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John, Master Automotive Technician
Category: Car
Satisfied Customers: 9176
Experience:  ASE A1-A8 & L1 Master GM Tech 40 years experience
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1998 gmc suburban: 4x4..turbo diesel..the gear ratio..highway

Resolved Question:

I have a 1998 gmc suburban 4x4 with the 6.5 turbo diesel. I am intrested in changing the gear ratio to make the truck better for highway use. i think it has the 3.73 now but it may be the 4.11 , it takes 2100rpm to hold it at 70. i have seen 3.08 on some of these and was wondering how much i should be looking to spend to change my 4x4 to this and if there is a higher ratio available than the 3.08? what would the drawbacks be to doing this ? i do not plan to ever tow heavy loads or use the 4x4 for anything extreme.
Submitted: 8 years ago.
Category: Car
Expert:  John replied 8 years ago.

Hello jcooper990,

The cost of replacing a ring & pinion gear set,pinion bearings,side carrier bearings,grease & sealer is around 1000.00 per axle.There are some higher ratio's.2.70,2.73,2.39,2.58 are what I see listed in a GM production option book.This would make a difference in torque output to the wheels at low speed ,but a 6.5 diesel should handle it well,a gas engine would most likely has an excessive engine clatter.If you changed it & ever did carry a load,this would be hard on the automatic transmission clutches.

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