Hello Suburban experts out there!

I'm looking for an advice to get the differential ratio changed to 3.42 from stock 3.08 on my 2015 Suburban LT 4WD.

Questions:
1. Do I need both front and rear ratio changed since it's a 4WD?
2. Any recommended mechanic in Chino, California?
3. What's the cost range?
4. I have the default factory tow receiver. Does that mean I have a transmission cooler?

Thank you in advance,

LK

 

Welcome to the forum.

1. Yes
2. Dealer would be a good start as I'm sure the computer will have to be reprogrammed for the different ratio.
3. Probably in the range of $3,000 to $4,000.
4. I believe you have to have the heavy duty trailer package to get the transmission and oil coolers.

 

I have heard and read good things about Superior Auto Styling in Ontario. They're located at 1125 North Hellman Avenue

 

Thank you!

 

Regarding the factory transmission cooler, just get a flashlight and look through the grill. It should be a stand alone square cooler in front of the rad. If you don’t have one they are easy enough to get installed. The engine oil cooler, if there is one, is integral with the rad. If you get under the driver side you should be able to see the lines exiting the block. The transmission cooler lines are on the passenger side and obviously are connected to the transmission.

SD

 

Not sure what you want lower gears for but what you are asking is not much of a jump. 3:73 might do you better. Thanks. *BW*

 

My opinion, FWIW

 

If it’s a 2015 you probably have the 8L90 transmission new for 2015. Are you able to manually select gears on it.?

When we talk about rear end ratios, people who are old enough think about a final transmission gear of 1.0 and then they might have a rear end of 3.08, 3.42, 3.73, 4.11. Most would say a 4.11 is the one to buy if you are planning on towing.

But things are different now. The final gear (8th) on a 8L90 is 0.65. 7th is 0.85. and 6th is 1.0. You can see that the top two gears are overdrive gears.

So if you want your truck to act like it it had a 3.08 rear end like the old days, all you have to do is select 6th gear and it will have a transmission gear ratio of 1.0 and a 3.08 at the rear. If you shift down to 5th manually, your transmission gear would be 1.67 and the combination of the transmission and the 3.08 rear end would make it would act like a 5.14 rear end. Unfortunately there is no combination to make it feel like a 3.42. If you want to change to a 3.42 rear end you can, but consider the cheaper option of just selecting a lower transmission gear.