upgrade differential ratio

1994 CADILLAC FLEETWOOD
115,000 MILES
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94FLEETWOOD
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Hi, I am planning on using my 94 Cadillac Fleetwood to tow a camper trailer. The diff. ratio it has is at 2.56:1 (not the best towing ratio).
I plan on upgrading to a 2.93:1 (from a Brougham) to increase the towing capacity to 5000lbs. Will this affect the pcm? Is there a tuning that must be done to the chip?
Aug 29, 2011 at 12:22 AM
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MHPAUTOS
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No change there is required, but with the different diff ratio you will get an inaccurate speedo reading, you may be able to change the speedo drive to one for a model with that ratio.
Aug 29, 2011 at 2:03 AM
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94FLEETWOOD
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Thanks for your input. The car has 235/75/15 tires on. Originally, it should run on 235/70/15. Would this slight difference in tire size compensate the speedo difference a little?
Aug 29, 2011 at 2:08 AM
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CADIEMAN
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their is about 4 to five gears with different teeth nunbers.make sure you have a good tranny cooler and a heavy duty radiator if possable.thanks for using 2carpros
Aug 29, 2011 at 9:30 PM
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MHPAUTOS
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It is only the dia of the trye that will alter spedo readings, both are 15" so ther is no differance there.
Aug 29, 2011 at 10:28 PM