Axle swap

[rideitall]

I have a 95 C1500, 4.3 V6, with the GU6 3.42 rear end ratio w/ drum brakes. I have an opportunity to get a 3.08 GU4 (I want the 3.08 since I don't tow and prefer the better mileage that should result) w/ disc brakes. Question: While I know the axle will bolt up, what changes will need to be made, if any, to accommodate the discs in the rear? Currently the system is ABS disc front/drum rear.

Thanks in advance from a new member.

 

[ChrisAU]

You could take the discs off the rear and just put your drums there without any modification. Where did you find a rear with discs though? The 99-06 10 bolts are different than 88-98s.

 

[rideitall]

It's claimed to be from a 92 GMC 1500 GU4 option w/discs and should bolt up fine but I'm not sure about the changing over to discs (If it does in fact have disc, I haven't seen it yet). Would like to keep 'em if it's do-able.

 

[outalne94z71]

It's claimed to be from a 92 GMC 1500 GU4 option w/discs and should bolt up fine but I'm not sure about the changing over to discs (If it does in fact have disc, I haven't seen it yet). Would like to keep 'em if it's do-able.

the only gmt 400 that i am aware of to have rear disk is the c3500hd you either have a converted axle or one from a newer truck

even the 454ss did not have rear disk

 

[DGA1]

It might be cheaper just buying a gear set, $150-$200 if you do the work yourself, and swap it.

 

[axisT6]

The additional load from the 3.08s may actually cause you to lose MPG. It is commonly thought that if you decrease RPMs (numerically lower gears) that mileage will improve. This is partly right. 3.08s will also put more load on the engine. Engine load has a more direct affect on MPG than RPM. Bear in mind also that you have a V6 in a fullsize truck. That engine will need all the help it can get. Depending on your tire size, you may want to switch to 3.73s or leave the 3.42s in and do simple engine mods to get more MPG.

You want a gear that allows you to be in the upper end of your torque curve most of the time.