Gear Swap Question, Experience Needed - DodgeIntrepid.Net Forums - Dodge Intrepid, Concorde, 300m and Eagle Vision chat
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post #1 of 35 (permalink) Old 11-13-2013, 01:43 PM Thread Starter
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Gear Swap Question, Experience Needed

Would like to say hello again, been away for quite a while. My new interest is in getting better mileage, all time best of 30.75mpg.

Anyway, I have the 3.89 gears already and i went cheap with used tires and have 215/60/16's so now my cruising rpm's are a bit high and really limit my mileage conquest. 2100rpm at 60.

QUESTION: Can the two sprockets at the rear of the transmission be transposed so the larger one is on the output shaft and the smaller one is on the diff. shaft?

Thanks.
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post #2 of 35 (permalink) Old 11-13-2013, 01:54 PM
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I am going to guess that the answer to that question is no. However, that particular gearset can be swapped out with the gearset out of a base model 300m which has a gear ratio of 3.66 instead of the 3.86 gears that are currently in your car.
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post #3 of 35 (permalink) Old 11-13-2013, 02:22 PM Thread Starter
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yes, but that only lowers cruising rpm by about 100 or so. I'd really like to get down around [email protected]
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post #4 of 35 (permalink) Old 11-13-2013, 02:25 PM
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if you want lower RPMs at 60mph you should put in the 3:66 gearset that come in 3.2L and 3.5L cars (non 300m special)
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post #5 of 35 (permalink) Old 11-14-2013, 12:33 AM
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Originally Posted by beeblebrox82 View Post
if you want lower RPMs at 60mph you should put in the 3:66 gearset that come in 3.2L and 3.5L cars (non 300m special)
This is your answer. 3.89 is what comes with 300M Special's and 2.7L LH vehicle's, it's the go-too for torque and speed. Only other options would be Prowler gears and Prowler Pro Gears. But performance options.

If you run some numbers and know your math and find it will be in more of your favor swapping output shaft and differential shaft gears; then it is an option. Providing both gears are not identical in tooth count (excuse me if I never counted them LOL).

Pretty easy procedure, more so with the transmission OUT of the car.

- Raise the vehicle. Level is recommended since you likely don't want to be showered in extra transmission fluid. But consider this a good time for a new gasket and filter.

- Put in a jack to support the transmission, if you secure it under the oil pan, I suggest a wood block across the entire pan to ensure nothing gets dented.

- Remove the six bolts on each side of the support beam, which connects to the body and engine cradle. CAREFUL, they will shear as they tend to corrode, suggest putting anti-seize on everything you put together that is steel-on-steel.

- Remove the four or six bolts securing to the transmission. CAREFUL, they will shear if they are built up with oxidization.

- Remove the gear cover.

To remove gears, just rotate the fancy clip until it lines up with the gear splines and pulls off. Gears slide off very easily.

You'll need to visit Dodge and get some ATV transmission sealant for the cover when sealing it back up.

Expect to loose 2-4 liters of fluid as well. Use ATF-4 ONLY. If you reuse your old fluid via catching it by a container, I SERIOUSLY recommend a paint strainer in the funnel with a magnet. This way all dirt and debris is caught.


That said, I get 30-35 MPG with my Police 3.5 with ported heads, new injectors, 3.89 gearing and shift kit, on autostick. Mind you I'm driving terribly, well - by the books and it feels slow and awful.

In the famous words of Jeremy Clarkson... POOOWWWEEEERRR!

Last edited by SRT6INTREPID; 11-14-2013 at 12:39 AM.
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post #6 of 35 (permalink) Old 11-14-2013, 06:46 AM
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There's no fluid in the area of the chain and sprockets is there?
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post #7 of 35 (permalink) Old 11-14-2013, 08:45 AM
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There's no fluid in the area of the chain and sprockets is there?
Yes there is, the ATF+4 provides the lubrication.
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post #8 of 35 (permalink) Old 11-14-2013, 12:52 PM
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Ahh. OK. Learned something. I see in the sketches of the chain area with the cover off in the FSM a "chain oiler" referenced.

Last edited by peva; 11-14-2013 at 12:58 PM.
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post #9 of 35 (permalink) Old 11-15-2013, 09:38 AM
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There's no fluid in the area of the chain and sprockets is there?
Yeah - I didn't think it was in the ATF sump either but it is.

You can easily loose 1-3L of fluid from the back cover alone.

I put in seven liters of fluid when I dropped the pan for a filter and the gear swap.
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post #10 of 35 (permalink) Old 11-17-2013, 12:23 PM Thread Starter
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Originally Posted by SRT6INTREPID View Post
This is your answer. 3.89 is what comes with 300M Special's and 2.7L LH vehicle's, it's the go-too for torque and speed. Only other options would be Prowler gears and Prowler Pro Gears. But performance options.

If you run some numbers and know your math and find it will be in more of your favor swapping output shaft and differential shaft gears; then it is an option. Providing both gears are not identical in tooth count (excuse me if I never counted them LOL).

Pretty easy procedure, more so with the transmission OUT of the car.

- Raise the vehicle. Level is recommended since you likely don't want to be showered in extra transmission fluid. But consider this a good time for a new gasket and filter.

- Put in a jack to support the transmission, if you secure it under the oil pan, I suggest a wood block across the entire pan to ensure nothing gets dented.

- Remove the six bolts on each side of the support beam, which connects to the body and engine cradle. CAREFUL, they will shear as they tend to corrode, suggest putting anti-seize on everything you put together that is steel-on-steel.

- Remove the four or six bolts securing to the transmission. CAREFUL, they will shear if they are built up with oxidization.

- Remove the gear cover.

To remove gears, just rotate the fancy clip until it lines up with the gear splines and pulls off. Gears slide off very easily.

You'll need to visit Dodge and get some ATV transmission sealant for the cover when sealing it back up.

Expect to loose 2-4 liters of fluid as well. Use ATF-4 ONLY. If you reuse your old fluid via catching it by a container, I SERIOUSLY recommend a paint strainer in the funnel with a magnet. This way all dirt and debris is caught.


That said, I get 30-35 MPG with my Police 3.5 with ported heads, new injectors, 3.89 gearing and shift kit, on autostick. Mind you I'm driving terribly, well - by the books and it feels slow and awful.

In the famous words of Jeremy Clarkson... POOOWWWEEEERRR!

I understand all the gear options. You say you have done the gear swap so here is a more specific question. Are the two individual gears in the transmission similar enough they could physically be installed "backwards". Call me crazy, but this is actually my goal.

Just curious, do you hand calculate your mileage or is it by the overhead display? I find my display to be anywhere from 15-25% optimistic.
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post #11 of 35 (permalink) Old 11-17-2013, 01:17 PM
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When I just had a set of gears in hand that I sold something seamed different between them besides the size. It might have been the hole size or number of splines.... just cant remember.

Here is a pic of them,



From this pic it does seam possible if the splines are the same number

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post #12 of 35 (permalink) Old 11-17-2013, 02:05 PM
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Originally Posted by ksa8907 View Post
I understand all the gear options. You say you have done the gear swap so here is a more specific question. Are the two individual gears in the transmission similar enough they could physically be installed "backwards". Call me crazy, but this is actually my goal...
This doesn't answer your question, but this will give you an indication of the results if you do it (of course, whether you can do it or not I guess depends on if the shaft diameter and keying are the same and if there's room for the 33- or 34-tooth sprocket inside the trans. output side of the case):
Attached Images
File Type: jpg Calculations.jpg (41.1 KB, 28 views)

Last edited by peva; 11-17-2013 at 02:07 PM.
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post #13 of 35 (permalink) Old 11-17-2013, 02:27 PM
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I do believe the gears can be interchangeable, but everything will be off speed wise and your low end would be so terrible, but supposedly MPGs will increase.
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post #14 of 35 (permalink) Old 11-17-2013, 02:33 PM
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Peva - Where did you find that chart?

It leads me to believe you can swap the gear locations but with some slow take-off
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post #15 of 35 (permalink) Old 11-17-2013, 02:47 PM Thread Starter
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thank you all for the info, chances for this working seem high enough, ill prolly give this a try soon. Also, instrumentation is no concern, i use the torque app so i can either correct the data coming from the computer or just use gps speed.

I'm not too concerned about "off the line" acceleration, it's not exactly stellar anyway.
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