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Re: rear axle swap
Grigg #1128477 Thu Oct 08 2015 03:52 AM
Joined: May 2001
Posts: 478
K
koolkar Offline OP
Shop Shark
Originally Posted by Grigg
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 **** 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!

Re: rear axle swap
koolkar #1128612 Fri Oct 09 2015 02:41 AM
Joined: Jun 2011
Posts: 3,544
E
Shop Shark
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.


'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
Re: rear axle swap
koolkar #1128898 Sun Oct 11 2015 02:05 AM
Joined: Mar 2011
Posts: 735
T
Shop Shark
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.


1946 1.5-Ton Chevy Shorty Bus
In the Stovebolt Gallery
More pix on Flickr

All my best --- Tango
Re: rear axle swap
Tango #1128952 Sun Oct 11 2015 01:11 PM
Joined: May 2001
Posts: 478
K
koolkar Offline OP
Shop Shark
Originally Posted by Tango
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?

Re: rear axle swap
koolkar #1128957 Sun Oct 11 2015 01:29 PM
Joined: May 2005
Posts: 9,146
G
.
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.


1951 GMC 250 in the Project Journals [stovebolt.com]
1948 Chevrolet 6400 [stovebolt.com] - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
1952 Chevrolet 3800 pickup [stovebolt.com]
---All pictures [picasaweb.google.com]---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-
Re: rear axle swap
koolkar #1128958 Sun Oct 11 2015 01:45 PM
Joined: May 2001
Posts: 478
K
koolkar Offline OP
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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.

Last edited by koolkar; Sun Oct 11 2015 01:47 PM.
Re: rear axle swap
koolkar #1128981 Sun Oct 11 2015 04:31 PM
Joined: May 2005
Posts: 9,146
G
.
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.


1951 GMC 250 in the Project Journals [stovebolt.com]
1948 Chevrolet 6400 [stovebolt.com] - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
1952 Chevrolet 3800 pickup [stovebolt.com]
---All pictures [picasaweb.google.com]---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-
Re: rear axle swap
koolkar #1129001 Sun Oct 11 2015 06:40 PM
Joined: Jan 2008
Posts: 4,661
C
Shop Shark
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.

Re: rear axle swap
koolkar #1129035 Mon Oct 12 2015 12:32 AM
Joined: Dec 2008
Posts: 392
F
Shop Shark
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.


1956 Chevy School Bus Superior Body
In the Stovebolt Gallery
More pix in Photobobucket
Re: rear axle swap
crenwelge #1129077 Mon Oct 12 2015 05:07 AM
Joined: May 2001
Posts: 478
K
koolkar Offline OP
Shop Shark
Originally Posted by crenwelge
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.


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.

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