The Stovebolt Site Forums The Parking Lot Big Bolts rear axle swap

I've been looking but can't find a topic regarding rear axle swaps for a 1 1/2 ton. I have the 2 speed vacuum shift that is stock. I also have a 95 chevy 3500 h.d. for a donor. I want to swap the entire axle assembly and use the cross member from the 3500 so I can have rear shocks. I realize I will probably will have to rework the drive shaft but am wondering about spring perch relocation. my back is hurt right now so I can't go measure.anybody know if I will have to relocate the perches? u bolts using the stock springs?

I used the same axle from a P30 chassis and had to move the spring pads. Think the 3500hd has same frame width, still be nice to measure and check.
Had you asked this morning I could have measured a 3500hd at lunch... A friend of mine runs a junk yard and had one on the roll back as he stopped for lunch too. Just a cab and chassis, would have been real easy to measure.

I have a 2015 3500HD. The frame rails are 34". Moving spring seats is no big deal. Just cut the old ones off and weld new ones on, It doesn't have to be a particularly good weld because the U-bolts are what does the holding. What are you going to do about wheels? A driveshaft shop can make any kind of driveshaft you need and they are not very expensive.

using the 19.5 tires and wheels. the c.o.e. already had the wheels changed when I bought it. guess i'll start calling spring shops tomorrow to try and find spring perches

by the way......

I assumed the 3500HD is one with an I-beam axle and 10 lug wheels, back when HD meant something. Seems everything now days is HD or Super Duty...

You may use the spring pads off the original axle as it, the Dana 80, and 70HD all have 4" axle tubes.

it is a 3500 h.d. with 10 lug 19.5 wheels. thanks for your help.

Although today's 3500HD is built with a pickup cab, they have more capacity than the old 3500 with 20". The wheels are 17" duals with 8 hole metric.

https://plus.google.com/11263693037...5156051106&oid=112636930370126476644

Thee trailer has 17.5 singles that carry as much as 16" dual with a lot less rolling resistance. Although I have a CDL, the single tires keep me under the radar with DOT hassle. Most troopers haven't been taught that 17.5 singles carry more than16" duals.
The term HD with a GMC is not just a macho term. Take a look at a 2015 3500HD GMC. It amazes me how they are build, and I have been around trucks for over 50 years.

ummmm...... about what, 16000 pounds of Emeryville there?

Yes, they're capable trucks.

With out side tracking this thread too much.. My point was if ALL the standard pickup trucks are now called "HD" and "Super Duty" then what do you call something that really is heavy duty in comparison to them? "Extra Super Duty", or "Extremely More So Heavy Duty"... I find the whole thing ironic and comical.

Grigg

I don't think you are side tracking at all. in fact, you make a very good point. especially when updating our old iron, the search for parts can be a difficult process. in my case, the donor truck came from 175 miles away, and I had to borrow a long enough trailer to load the thing. imagine if it had been a 3500 with 8 lug wheels instead of a real h.d.. all that time and money wasted as well as a day off work for nothing.

you make a very good point about the manufacturers calling things by different names for marketing purposes. it's the same old thing in a different bag and can lead to confusion, loss of time and money and getting REAL [censored] at the outcome. perhaps time for reminder to be very specific when you order or buy something that you cannot see in front of you to avoid confusion. in this case I was well aware of the difference in the 3500 series and asked about the lug nuts before committing. I also asked for pictures and measurements to make sure the thing would fit the trailer. it did, with about 3 inches to spare.

actually.............. this sidetrack has a great deal of merit. thanks!

I put P 3500(baby school bus) running gear under my '37 GMC, using the Saginaw power steering box and hydroboost. I was able to move the fenders out 1.5" to accommodate the stock 3500 front axle. For a 1.5 ton, put P30 spindles on a 2 ton axle(stories here) use 3/4 ton power steering box.

I went with a Dana 80 HD out of a '98 Chevy 3500 for my '46 1-1/2 ton School bus. Had to relocate the spring perches about 7/8" outboard but had tons of gearing options plus it came with disk brakes. Good fit overall with no issues.

another question. what did you use for a master cylinder? how did you fit it?

If you have the whole 3500HD truck and will be using brakes from it then use the MC and booster from it. Already a good system from the factory, no reason to look for something else.

the 3500 was a burn out. master cylinder (hydro vac) was burned pretty bad. took only the back axle and sent the rest to the scrap yard. local zoning prevents keeping junk cars. so, until I find a p-30 front axle, it's front drums and rear disc brakes. by the way, this is a cab over. no place to mount a brake booster without butchering. thinking i'll have to spring for a new booster/ master cylinder that mounts to the frame under the floor. then will need a new proportioning valve/ check valve. options for that are 2 lbs. or 10 lbs.. by the way. i'm keeping the 235 as it only has 39,ooo miles. coming up with a power steering setup won't be easy i'm thinking.

I can't advise on rear disc and front drums, never tried it and generally not recommended.

In mounting your MC consider putting it under or even behind the cab wherever is enough room, and use a long pushrod from the original pedal.

If you won't be using PS then a common vaccum booster and MC is a great choice. Don't need hydroboost if you won't have a PS pump.

Depending on the MC and proportioning valve you use either may include residual pressure valves. If you need individual ones then 10psi are for drum brakes and 2psi for disc brakes.
I used a standard brass GM style proportioning valve (2 inlets 3 outlets) and also used a pair of 2psi residuals, MC is under the floor.

I would be very cautions with disc brakes on the drive and drum on the steer. Having more braking action on the drive is what causes you to switch ends on slick pavement. I was a licensed salvage dealer for many years. I stayed away from anything that had a fire. Fire distorts things that you would never believe it could distort.

I put in a new axle in my 56 1 1/2 tone with rear disc brakes. 10 lug pattern same as the original. Went from a 6.17 gear ratio to 4.63. Spring pad difference was 3/8" overall center to center so I open the alignment hole 3/16" on either side to fit. The axle I used was from a 2001 HD3500 truck. I drove it a couple times and the brakes functioned just fine. I did keep the hydrovac in and put in a new stock MC. I put in a residual valve going to the rear discs. The axle tubes are the same diameter as my stock axle so I reused the part that clamps to the axle with the U bolts and has integrated shock mounts. I did get new U bolts for it though as recommended. I have drum on the steer axle still, but have acquired a stepvan and took the front axle for the disc brake swap that Grigg described in another post. I also kept the rear axle because it was in great shape, longer gears and disc as well. Thought someone could use it for a swap too. It's a Rockwell Model C with 5.29 gears.

fire was in the engine compartment. very little cab damage and no damage further back. had a 40 gallon gas tank that was undamaged. (I kept that). getting good and useful info from you guys. thanks. keep it coming.

My Dana 70HD came from an 80's P30 motor home chassis and if I remember correctly I moved the spring pads 1" each to the outside.

Helped a friend with a Dana 80 for his 53 GMC 2 ton and it lined up perfectly, spring pads were already the right width. We never could figure out what the axle came from but my best guess is an Oshkosh step van, it had 6 lug Budd wheels.

I will be installing a 3500 master on my rig with the Dana 80. It now has disks all around. Hope to get started on that fun trip soon.

Correction to the Master Cylinder question...

Mine is actually from a c-2500...not 3500. Sorry 'bout that.

I will be starting the hanging process pretty soon but have to do a fair amount of fabricating around it.