Here is a photo of the revised low/reverse accumulator piston assembly, showing the new one-piece cap with the attached Viton seal just above the snap ring:

 

@pt500 I think in this thread or the referenced wrangler thread there was an indication that later transmissions had the one piece cap. I assume the cap is the piece leaning on the sharpie?

A lot of good diagrams of internal parts but I don't see any of where to reach this accumlator in the transmission and whether you could do it with the transmission in the (jeep) in this case. This is a 2011 wrangler that was one of the later models to have the 42 RLE and presumably might have had the updated cap so maybe I shouldn't imagine I could get out of no reverse this easy. Just following up for any knowledge and the wrangler thread is kind of old so I don't know what kind of response i'll get rebooting it.

But a great find and glad you brought the link forward in this thread.

thanks AT

PS This transmission was "rebuilt" about a year and a half ago. I assume that if it had the old style cap it would have been replaced at that point although I'm not always sure that "rebuilt" means doing more than some minimum to fix obvious problems rather than complete refitting.

 

Edited/corrected below: When removing the valve body (after removing the filter), just remove the several hex bolts attaching it to the transmission. Do not remove the black Torx screws; they hold the valve body together. See the Factory Service Manual and Youtube videos on the 42LE or A606 valve body for further clarification on removing the valve body.
-----
Replying to archibald tuttle (answers to questions below):

Sorry I'm late getting back to this - I don't have notifications set up for the discussion threads (too busy with other life stuff). For others that might be reading this, I will include a lot of basic info that you may already know.

I would think that your 2011 Jeep transmission had the updated cover/cap. If your transmission was rebuilt, I suppose it is possible (but ulikely) that they somehow used an old style cover/cap and O-ring in the low/reverse accumulator bore if those were included in the rebuild kit instead of a new-style cover. A rebuild should have replaced all the wear parts including all the internal seals that I believe can also cause no reverse. A good shop would use a brand-name "master rebuild kit" that has several dozen parts (you can see pictures of all the parts in the kits on ebay if you search on 42LE or A606 plus "rebuild kit.")

For some reason I don't think the Mopar technical service bulletin (TSB) I listed ever showed up on the Intrepid TSB list and maybe not on some of the Jeep TSB lists either.

To clarify again, as I said the above bulletin was BEFORE they came up with the permanent fix by using the new one-piece cover (without the separate O-Ring) with the AB suffix (4431617AB or 04431616AB). 4431617 without the suffix was the old cover that used the separate (flimsly) O-ring that broke. So the parts they are listing in the TSB are just replacing the broken O-ring and cover with the same old style. I couldn't find a TSB that references the new cover, but there must be one somewhere. Sonnax and Transtec may also have published something in their transmisson service bulletins for shops.

A good transmission shop would obviously check for this and install a the new cover and snap ring if needed. As the guy in the Jeep thread mentioned, there are also Sonnax brand repair kits if the accumulator bore is worn at high mileage. The ATRA certified trans shop guys should know all about the variouis fixes on the 42LE/A606 transmissions - they use Sonnax, Transtec, etc. parts all the time and and have access to their database with all the bulletins.

By the way, I think that Jeeps used on rough roads or off-road might be especially susceptible to the old cap and O-ring failure because maybe the low/reverse accumulator piston and springs could bounce on the top of the cap in a big bump and break the old O-ring like the guy showed in the Jeep thread (but that is just speculation).

As I recall, there were also some old threads on this website that cover other causes of 42LE/A606 "no reverse," but I wasn't able to locate them with the advanced search function (it isn't great). They may have been archived and no longer searchable. The other Chrysler/Dodge/Jeep websites probably also have threads on the subject since so many vehicles used that transmission.

One other easy thing that a trans shop can check is the two transmission speed sensors (they screw into the side of the transmission). I believe if at least one of the speed sensors (output sensor?) is bad (or its wiring\connector\nearby ground wires deteriorated, causing electrical noise), it can lock out reverse because it tells the trans control module that the vehicle is in forward motion. The speed sensors and cables are easy for a shop to check and replace/repair. Good sensors are from Standard Motor Products or Echlin (NAPA brand) - but get their regular line, not the economy line. Also for an electrical cause, a check of all cabling running to the transmission, solenoid switch, and trans control module is called for, as well as checking the ground cables for good attachment and any deterioration.

For a complete diagnosis a good ATRA certified shop (atra.com) should be able to do a scan for transmission diagnostic codes with their Snap-On (or similar) scanner. A shop can also do pressure tap tests tests on the transmission without removing it. You can't really "diagnose" anything by removing the transmission; that would be like pulling the engine to do a compression test. All the transmission tests and a bunch of diagnostic tables and flow charts are in the Mopar Factory Service Manuals for the car year in the transmission section (pdfs on this site for Intrepids and maybe on the Jeep sites too). There are also more detailed Mopar supplementary transmission service manuals for the cars and Jeeps (sometimes available on ebay). The shops likely have these supplementary manuals and bulletins in their databases.

Your questions:

Yes the later one-piece cover/cap is the part on the yellow sharpie shown in the photo.

As I wrote, I believe the new covers have been used in production transmissions starting around 2004-2005, but the best way to confirm that for Jeeps would be to look at the exploded view valve body parts diagrams in the dated Mopar parts catalog for the year of the vehicle and compare them to two I posted above that are from a single page right after the valve body parts listing. There are some of those parts catalogs on this site for Second Generation Intrepids of those years in pdf format, and the Jeep and other Mopar car websites may have them also for the later years.

As far as servicing, the accumulator bore where the cover resides (and holds in the piston and springs) is in a cylindrical bore in the transmission above the valve body as shown in the TSB pdf I linked to and attached. And no, the transmission does not have to be removed to remove the valve body and access the accumulator bores (there are three above the valve body and one contained in the side of it). The Factory Service Manuals (some in pdfs also on the websites) explain the procedure. The trans shops do it all the time if the diagnosis indicates a possible valve body problem. They can also just remove/replace the solenoid switch (often called the solenoid pack) mounted to the valve body if the diagnosis indicates a possible problem there - remanufactured ones are still available for that. (On early versions of the Chrylser Ultradrive transmission the solenoid switch may have been mounted externally on top of the transmisson.)

The four accumulator pistons have two inexpensive teflon rings that can wear, but are easily replaced. I think the accumulator bores can also wear in normal service, but like the guy in the Jeep post said, there are Sonnax repair kits for that. If there is a problem with the valve body itself that can't be repaired with a different type of Sonnax kit, remanufactued valve bodies are probably still available to the trans shops, but they are probably at least a couple hundred dollars.

I assume that you will be taking it to a transmission shop, which is really best. The ATRA trans shop mechanics know all this stuff. But this is what would be invovled to check for the updated cover and accumulator bore wear/damage:

The valve body is on the bottom of the transmission and can be accessed by dropping the pan and draining the fluid, then removing the filter (very messy and can spill trans fluid all over). There is a very slow way to first siphon some of the fluid out of the fill tube first so it isn't so messy. And then to get to the accumulator bores and pistons (one of which has the cover which is held in place by the snap ring) you have to remove a few bolts supporting the valve body. Do not remove the black Torx screws; they hold the valve body together - see the FSM and Youtube videos for clarification on removing the valve body. Some of the bolts may be different lengths (can't recall); if so, you've obviously got to pay attention to that and record the different hole locations. And you also have to do a procedure explained in the FSM to position the shift linkage/manual shaft to get the valve body to drop without hanging up - a bit tricky. It has to be in the same position for insertion of the valve body.

The sealing ring on the shifter shaft that extends up from the valve body may also cause some slight resistance when lowering the valve body. This "seal, manual valve lever" (p/n 4412836 or 04412836) along with another small "seal, 2nd & 4th clutch feed" (4412291 or 04412291) and a tiny cone-shaped filter "screen, regulator valve" (3878313 or 03878313), all on the valve body, can can also be replaced with aftermarket parts that are still available to the shops or online. They are inexpensive.

So it is a difficult, tedious, messy job on your back at home, but taking off the valve body to check for this failure in the low/reverse accumulator cover and any accumulator bore wear/damage is actually a relatively easy job for a trans shop with the car on a lift.

As I said, a good ATRA-certified transmission shop (for shops, see American Transmission Rebuilders Association, ATRA.com), should be able to access all the info on this fix as well as the other possible ones for no reverse in their service bulletin databases (published by both both Mopar and the transmission parts suppliers).

As far as the parts, the accumulator pistons and teflon rings are still available from the trans shop's parts suppliers if those are needed. There are aftermarket parts, but I believe the Mopar interchange part numbers are 4446620 or 04446620 for the accumulator piston and 4446544 or 04446544 for the teflon rings (2 on each piston). All the parts are shown in the Mopar parts catalog exploded diagrams and tables (as I said pdfs for different years on this site and probably the Jeep sites too).

And as I said the new cover part number is 4431617AB or 04431617AB (either is correct), or I think the aftermarket numbers are A92949A and B82053. The snap ring number is either 6501695 or 06501695 and if you've got an old broken one to match it is very close to the size of a standard snap ring size available at good hardware stores which may work. (But check the exact thickness with the old one so it will fit in the slot). Both parts are still available through local and some online Chrysler/Dodge/Jeep Mopar dealers. If you want to buy them to take a look or discuss with the mechanics at a shop, ebay sellers also sometimes have them. Here are a couple links as of 6/23 (same seller):

Transtec B82053 Cover, Accumulator Low/Reverse

Cover Accumulator Low / Reverse Bonded. 194506093854 | eBay

Find many great new & used options and get the best deals for Cover Accumulator Low / Reverse Bonded. at the best online prices at eBay! Free shipping for many products!

www.ebay.com

$7.56 shipped

Mopar D92896 Snap Ring; Reverse Accumulator Cover A604 (41TE), 42 LE, 41TE, 41AE

Mopar D92896 Snap Ring; Reverse Accumulator Cover A604 (41TE),42LE,41TE,41AE | eBay

Find many great new & used options and get the best deals for Mopar D92896 Snap Ring; Reverse Accumulator Cover A604 (41TE),42LE,41TE,41AE at the best online prices at eBay! Free shipping for many products!

www.ebay.com

$3.35 shipped

If you take it into a shop, let us know what they diagnose and repair for the no reverse.

The LH cars were a great leap forward for Chrysler, but Lee Iacocca could have saved us all a lot of trouble if he had the Chrysler engineers do more stress testing on the various Ultradrive transmissions.

 

Replying to archibald tuttle (answers to questions below):

Sorry I'm late getting back to this - I don't have notifications set up for the discussion threads (too busy with other life stuff). For others that might be reading this, I will include a lot of basic info that you may already know.

I would think that your 2011 Jeep transmission had the updated cover/cap. If your transmission was rebuilt, I suppose it is possible (but ulikely) that they somehow used an old style cover/cap and O-ring in the low/reverse accumulator bore if those were included in the rebuild kit instead of a new-style cover. A rebuild should have replaced all the wear parts including all the internal seals that I believe can also cause no reverse. A good shop would use a brand-name "master rebuild kit" that has several dozen parts (you can see pictures of all the parts in the kits on ebay if you search on 42LE or A606 plus "rebuild kit.")

For some reason I don't think the Mopar technical service bulletin (TSB) I listed ever showed up on the Intrepid TSB list and maybe not on some of the Jeep TSB lists either.

To clarify again, as I said the above bulletin was BEFORE they came up with the permanent fix by using the new one-piece cover (without the separate O-Ring) with the AB suffix (4431617AB or 04431616AB). 4431617 without the suffix was the old cover that used the separate (flimsly) O-ring that broke. So the parts they are listing in the TSB are just replacing the broken O-ring and cover with the same old style. I couldn't find a TSB that references the new cover, but there must be one somewhere. Sonnax and Transtec may also have published something in their transmisson service bulletins for shops.

A good transmission shop would obviously check for this and install a the new cover and snap ring if needed. As the guy in the Jeep thread mentioned, there are also Sonnax brand repair kits if the accumulator bore is worn at high mileage. The ATRA certified trans shop guys should know all about the variouis fixes on the 42LE/A606 transmissions - they use Sonnax, Transtec, etc. parts all the time and and have access to their database with all the bulletins.

By the way, I think that Jeeps used on rough roads or off-road might be especially susceptible to the old cap and O-ring failure because maybe the low/reverse accumulator piston and springs could bounce on the top of the cap in a big bump and break the old O-ring like the guy showed in the Jeep thread (but that is just speculation).

As I recall, there were also some old threads on this website that cover other causes of 42LE/A606 "no reverse," but I wasn't able to locate them with the advanced search function (it isn't great). They may have been archived and no longer searchable. The other Chrysler/Dodge/Jeep websites probably also have threads on the subject since so many vehicles used that transmission.

One other easy thing that a trans shop can check is the two transmission speed sensors (they screw into the side of the transmission). I believe if at least one of the speed sensors (output sensor?) is bad (or it's wiring or connector deteriorated), it can lock out reverse because it tells the trans control module that the vehicle is in forward motioin. The speed sensors and cables are easy for a shop to check and replace with good ones like from Standard Motor Products or Echlin (NAPA brand) - their regular line, not the economy line. Also for an electrical cause, a check of all cabling to the transmission and trans control module is called for, as well as checking the ground cables.

For a complete diagnosis a good ATRA certified shop (atra.com) should be able to do a scan for transmission diagnostic codes with their Snap-On (or similar) scanner. A shop can also do pressure tap tests tests on the transmission without removing it. You can't really "diagnose" anything by removing the transmission; that would be like pulling the engine to do a compression test. All the transmission tests and bunch of diagnostic tables and flow charts are in the Mopar Factory Service Manuals in the transmission section (pdfs on this site for Intrepids and maybe on the Jeep sites too.)

Your questions:

Yes the later one-piece cover/cap is the part on the yellow sharpie.

As I wrote, I believe the new covers have been used in production transmissions starting around 2004-2005, but the best way to confirm that for Jeeps would be to look at the exploded view valve body parts diagrams in the dated Mopar parts catalog for the year of the vehicle and compare them to two I posted above that are from a single page right after the valve body parts listing. There are some of those parts catalogs on this site for Second Generation Intrepids of those years in pdf format, and the Jeep and other Mopar car websites may have them also for the later years.

As far as servicing, the accumulator bore where the cover resides (and holds in the piston and springs) is in a cylindrical bore in the transmission above the valve body as shown in the TSB pdf I linked to and attached. And no, the transmission does not have to be removed to remove the valve body and access the accumulator bores (there are three above the valve body and one contained in the side of it). The Factory Service Manuals (some in pdfs also on the websites) explain the procedure. The trans shops do it all the time if the diagnosis indicates just a possible valve body problem. They can also just remove/replace the solenoid pack above the transmission if the diagnosis indicates a possible problem there - remanufactured ones are still available for that. The four accumulator pistons have two inexpensive teflon rings that can wear, but are easily replaced. I think the accumulator bores can also wear in normal service, but like the guy in the Jeep post said, there are Sonnax repair kits for that. If there is a problem with the valve body itself that can't be repaired with a different type of Sonnax kit, remanufactued valve bodies are probably still available to the trans shops but they are a few hundred dollars.

I assume that you will be taking it to a transmission shop, which is really best. The ATRA trans shop mechanics know all this stuff. But this is what would be invovled to check for the updated cover and accumulator bore wear/damage:

The valve body is on the bottom of the transmission and can be accessed by dropping the pan and draining the fluid, then removing the filter (very messy and can spill trans fluid all over). There is a slow way to siphon the fluid out of the fill tube first so it isn't so messy. And then to get to the accumulator bores and pistons (one of which has the cover which is held in place by the snap ring) you have to remove several Torx screws supporting the valve body. As I recall, I think (?) some screws may be different length, so you have to pay attention to that. And you also have to do some careful things explained in the FSM with the shift linkage to get it to drop without hanging up - a bit of a pain.

The two other accumulator pistons with springs inside are loose and can fall out when the valve body is dropped down. The aluminum pistons and their sealing rings can be damaged if you drop them (the rings are replaceable). Then you can access the low/reverse accumulator (which is supposed to be held in by a snap ring, but as the Jeep post said, it can be broken). Those other two loose accumulors are tricky to get back in properly - you have to use a thin rigid plastic sheet to hold them in place as you bolt the valve body back on with the several screws.

So it is a difficult, tedious, messy job on your back at home, but taking off the valve body to check for this failure in the low/reverse accumulator cover and any bore wear/damage is actually a relatively easy job for a trans shop with the car on a lift.

As I said, a good ATRA-certified transmission shop (American Transmission Rebuilders Association, ATRA.com), should be able to access all the info on this fix as well as the other possible ones for no reverse in their service bulletin databases (published by both both Mopar and the transmission parts suppliers).

As far as the parts, the accumulator pistons and teflon rings are still available from the trans shop's parts suppliers if those are needed. There are aftermarket parts, but I believe the Mopar interchange part numbers are 4446620 or 04446620 for the piston and 4446544 or 04446544 for the teflon rings (2 on each piston). All the parts are shown in the Mopar parts catalog exploded diagrams and tables (as I said pdfs for different years on this site and probably the Jeep sites too).

And as I said the new cover part number is 4431617AB or 04431617AB (either is correct), or I think the aftermarket numbers are A92949A and B82053. The snap ring number is either 6501695 or 06501695 and if you've got an old broken one to match it is very close to the size of a standard snap ring size available at good hardware stores which may work (but double check the thickness). Both parts are still available through local and online Chrysler/Dodge/Jeep Mopar dealers. If you want to buy them to take a look or discuss with the mechanics at a shop, ebay sellers also often have them. Here are a couple links as of 6/23 (same seller):

Transtec B82053 Cover, Accumulator Low/Reverse

Cover Accumulator Low / Reverse Bonded. 194506093854 | eBay

Find many great new & used options and get the best deals for Cover Accumulator Low / Reverse Bonded. at the best online prices at eBay! Free shipping for many products!

www.ebay.com

$7.56 shipped

Mopar D92896 Snap Ring; Reverse Accumulator Cover A604 (41TE), 42 LE, 41TE, 41AE

Mopar D92896 Snap Ring; Reverse Accumulator Cover A604 (41TE),42LE,41TE,41AE | eBay

Find many great new & used options and get the best deals for Mopar D92896 Snap Ring; Reverse Accumulator Cover A604 (41TE),42LE,41TE,41AE at the best online prices at eBay! Free shipping for many products!

www.ebay.com

$3.35 shipped

If you take it into a shop, let us know what they diagnose and repair for the no reverse. Lee Iacocca could have saved us all a lot of trouble if he had the Chrysler engineers do a few more months stress testing on the 42LE/A606 transmission.

You have quite extensive knowledge of the subject - an area that I know very close to nothing about.

I will comment on this one group of sentences:

One other easy thing that a trans shop can check is the two transmission speed sensors (they screw into the side of the transmission). I believe if at least one of the speed sensors (output sensor?) is bad (or it's wiring or connector deteriorated), it can lock out reverse because it tells the trans control module that the vehicle is in forward motion

The speed sensor output signals are single-wire binary pulses (5 volts, ground, 5 volts, ground,...). I believe that any credible failure of one of the speed sensors will result only in a reduced number (usually zero, never more) of pulses. Also, the sensor output signals contain no direction (forward vs. reverse) information. The only speed signal schemes that I know of that also provide direction (in addition to speed amplitude) information are those with quadrature signals (utilizing multiple wires/signals per "sensor"), and the sensors on these cars are single-signal/wire sensors.

Having said all of that, no reason not to verify that the speed sensors are properly working.

I'm open to being told that I misunderstood some of what you said or that anything I said is not correct. And this is only a small part of all that you said (which, again, I have close to zero experiential/practical knowledge about). 👍

 

RMP RPM

👍

 

RMP RPM

👍

Thanks, fixed them. Getting old, like the car.

 

I think they are saying in this article below that at least on the AW50-40/42LE transmission it is is also possible to swap the input and output speed sensor connectors, which would also cause no reverse. If so, then best to only replace one sensor at a time to not confuse the two wires and connectors. And/or label them.

Edit 1: I looked at the spare sensors I have, and on the 1st Gen Intrepid 42LE at least, yes the pins and plugs are identical, however the connector locking tab is 180 degrees different. But I supposed you could force it and mistakenly swap them.

Aisin AW 50-40/42LE No Reverse After Overhaul

Aisin AW 50-40/42LE No Reverse After Overhaul

Problem:After overhaul or R&R of the transaxle, the transmission will not get Reverse from Neutral or Park. If the transmission selector is placed in Dri

www.sonnax.com

Edit 2: Here's another article below that spells out what the transmission control module (TCM) may also be doing on the 42LE and similar transmissions when it locks out reverse due to a faulty output speed sensor signal:

"The cause may be that during installation, the vehicle-speed sensor was placed into the location of the turbine-shaft-speed sensor on the case. This will create a vehicle-speed reading in the Park position because of the turbine shaft’s rotation in the Park position. The transmission control module will cancel Reverse application by turning on solenoid 1 to block the application of the B3 clutch, which is the low/reverse clutch. Once the selector is placed into Drive, the turbine shaft will come to a stop and Reverse will apply from the Drive position. "

Transmission Digest March 2005 (my favorite magazine for light reading)

March 2005 Issue - Transmission Digest

Issue Summary: We provide exploded views of the valve body and identification of components in AW50-42LE units. After overhaul, the speedometer on a Volvo/SAAB vehicle equipped with a 50-40 LE series transaxle may register in the Park position, and there may be no Reverse when the driver selects...

www.transmissiondigest.com