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Discussion Starter #1 (Edited)
new TCM with 2.7 gears?

I'll be replacing my 3.2 SE gears with gears from a 2.7 shortly. If I want to correct the speedometer due to the final drive ratio change, the TCM needs to be replaced, correct?

If that is the case, does this module also retain the VIN of the car, and thus would need "reflashing", or is it a direct-drop swap?

thanks :)
 

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All modules in the car don't NEED to be reprogramed except for skim and PCM. But for proper operation they will need to be programed usein a DRB. The pinion factor has to be set or your speedometer wont work. Otherwise the TCM SHOULD come pre-programed. The shop from where you order it from should be able to tell you if it is a dead box or if it is programed. If it comes programed they will need your VIN and mileage to order the part. I have ordered a few modules for customers car's nothing for an intrepid yet, but even something so much as a radio for a caravan they needed the vin and mileage to order the part.
 

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Discussion Starter #3
So I would have to go to a Dodge Dealership and order a new TCM specifying my VIN, mileage, and the new gear ratio, or could a technician use the DRB to change the pinion factor in my current one?

Any idea on cost of a new TCM if that's the route I need to have a proper speedo reading?
 

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you can change the pinion factor any time you want. But you can specify a custom pinion factor on these cars. You only have three different tire sizes to pick from. Yopu can NOT change gear ratio. If a TCM for an intrepid is like every other module I have ordered, yes the dealer will need your VIN and mileage. They cant order a module by gear ration. You might be lucky and find the part number for a TCM that has the gears your looking for, but chrysler has so many part numbers it can be pretty hard to find.
 

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Discussion Starter #5
gotcha.

any idea of which pinion factor the 2.7 has? or a chance the technician might know it?
 

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The gear ratio is part of the main program in the TCM - changing it isn't gonna' help you get the speedo corrected for the 3.89 gears. Only 2.7L and 300M Special PCM's have the correct gear ratio.

I've heard rumors of a couple of after-market things that can adjust the speedo but you'll have to research that ...
 

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Discussion Starter #7
I'm not sure I follow D76. As mentioned above, the gear ratio cannot be changed by the TCM. The gear ratio is determined by the gears themselves.

But the pinion factor in the TCM can be changed. This is the multiplication factor that the computer uses when reading the output shaft sensor (correct?) and multiplies by to get the speedo reading.

What I need to know is which pinion factor I need to have the TCM reprogrammed to.
 

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The pinion factor is merely the tire size - and all the factory sizes are so close that there's virtually no change between them. Here, you do the math ...

225/60/16
225/55/17
245/45/18

All well within ±1% of each other - not nearly enough to make up for the 3.89/3.66 (~6.3%) change you're talking about ...
 

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Discussion Starter #10
the Kenne Belle Optimizer II can be reprogrammed for 2.7 gears to correct the speedometer?

SWEET!
 

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Discussion Starter #12
2000, yep

thanks for all the help guys, I'll get the KB
 

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SPOOK R/T said:
As long as it is a 1998 to 2001 models.
95PGTTech said:
2000, yep

thanks for all the help guys, I'll get the KB
I think Spook is refering to the years K-B covers, not the correction for the gear ratio. K-B doesn't correct for that, either - sorry. But they do make a great program for the PCM ...
 

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Discussion Starter #14
I'm lost again now, sorry :(

Am I going to need a 2.7 TCM to get my speedo to be corrected?
 

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There are some other black boxes (not PCMs) out there that are supposed to correct for the speedo. I don't know who makes them or if they're even still around but some members have had them. I don't think the 2.7L will run your 3.2 very well - though others have used a 2.7L PCM to run a 3.2L engine I doubt it's an optimal program. I guess I just don't see what the big issue about the speedo is - you won't be anywhere close to the first guy to run 3.89 gears without correcting for them ...
 
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