Cummins Diesel Forum banner

rear end swap questions

2K views 13 replies 7 participants last post by  GreaseDog 
#1 ·
hey guys, i have a 96 3500 extended cab that left the factory as a dually. the PO removed the rear fender extensions, and the DRW spacers on the front axle and installed regular SRW wheels on it. after looking at wheel and tire options (19.5, 22.5, 24.5) i've decided that i'm not going to put the fenders and spacers back on it. instead, i'm going to put the set of 37 x 12.50 Goodyear MTRs i have in the garage on it.

this leads me to my problem... the rear end is too wide.

i have in my posession a GM single rear wheel 14 bolt full float rear end that has been completely rebuilt, new everything... it's got a Detroit Locker in it, and has been converted to disc brakes (79 Chevy K20 front brakes). no worries on incorrect position of the spring perches or shock mounts, as they've already been cut off of the axle for swapping into another truck i own. basically, i'm just cannibalizing the truck for parts now.

my questions are as follows:
1. is it going to be the right width? how wide is the SRW axle from wheel mount to wheel mount?

2. what will the disc brakes do to my ABS? can i just eliminate it altogether if the discs mess with it?

thanks in advance!
 
See less See more
#2 ·
If you put the fenders back on the truck, the 12.50 inch wide tires will still be under the fender. I had 10.50 inch wide tires and there was plenty of fender to cover the wheels and tires.
 
#3 ·
i'm not sure what you're getting at here... i want to install the 37s (4 of them, on 9" wide wheels) , and install a narrower rear axle... no more dually. as it sits now, on stock SRW wheels, with 245 70 16s, the tires stick out of the fenders by about 2".
 
#4 ·
What are you going to do with the front? Are you going to swap a shorter axle in there also? Won't the 37's stick out past the fenders with the stock axle? Do you own a tape measure? If so, measure the axle currently under the truck and measure the GM axle and see if the difference is what you want. Does your truck have four wheel or two wheel ABS? Does the GM axle have wheel speed sensors on each side for the ABS, one in the middle like the Dodge or no sensor at all? Is your truck currently rear disc? If not, then changes will have to be made for the installation of disc on the rear since disc and drum are world's apart in stopping power.
 
#6 ·
i am going to leave the front as it is. the spacers have been removed, leaving me with a standard non-dually front axle.

yes, the 37s will stick out past the fenders... as it sits right now, with the dually axle in the back, and stock wheels (non-dually wheels), the tires are a good 2" outside the fenders in the back. the front is exactly like it would be stock. i'm curious as to what the rear end SHOULD be, if it were a SRW truck.

no, the rear axle has zero provisions for ABS, as it came out of a '73 Chevy. i'm not completely sure what the ABS system consists of. the truck is currently buried in the back of my shop, and i'm just trying to get my ducks in a row before i pull it out and tear into it.

as for swapping to disc brakes, ABS aside, the only thing i'll need is the adjustable proportioning valve. disc brakes take less pressure to stop than drums. like i said, this axle is being cannibalized from another truck that has been my project for several years.

the only info i really need is the stock width of a non-dually axle, and what i need to do to eliminate ABS.
 
#5 ·
You will probably have to put an adjustable proportioning valve in the brake system to get enough fluid pressure to work the back brakes if you use disk brakes back there. Drum brakes take far less fluid pressure than disk brakes from what I've always understood.
 
#7 ·
your going to run into more than an ABS issue.

Because the rear axle has a tone ring (speed sensor), that is what the PCM uses i believe for ABS and the speedo/cruise.

Your oldschool axle obviously doesnt have the provisions for such a setup. but im curious if a guy couldnt modify the tcase speed sensor to work for everything...
 
#8 ·
The ABS is simple if you dont are about ABS. Unplug the module under the hood, pull the light out of the dash. You will stop quicker without ABS, but you have the ability to lock the tires up. i agree that you'll probably want to get a proportioning valve to get the brake bias right.
 
#13 · (Edited)
I once had 94-01 dodge front Dana 60 srw in my garage. It measured to 72" wms-wms.

If your 14b end up too narrow, you can just run wheel spacers to widen it up to match the front.

Also, I'm pretty sure your 14b don't have parking brake now too.
 
#14 ·
planning on ditching the front unit bearings using Ford parts, so i'm gonna lose ABS compatibility at all 4 wheels anyways...

as for the parking brake, i can use a driveline brake mounted to the back of the transfer case. more holding power than a pair of wheel mounted parking brakes anyways.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top