The Stovebolt Site Forums The Parking Lot Big Bolts 3600 rear end

Greetings to the truckmeisters out there. Hoping to learn about my new truck, a '57, 3600 with a dandy little dump bed that I just learned (thanks to this website, "advanced design", oh my gosh!!!)is not a one ton like I was told when I bought it, but a 3/4 (guess I overloaded it a wee bit). Also learned that it wasn't the 283 he said it was but a 350 truck motor from the mid 70's. After upgrades to the ignition and carb, unraveling the bird's nest he called wiring, sandblasting, painting and working towards general respectability (I probably won't be using valet parking just yet) I'm at the rear end. It's geared so low it's downright abusive. At 50mph that engine is really whirlin'. The drive shaft turns 4 1/2 turns for one of the wheel. I guess this makes it a 4.57 or some such but I'm told they don't make gears for this 10 bolt, 11 inch GM (a very small market). I hauled 4000lbs and took off in 2nd, uphill no prob. Plenty of power and torque. I know I can buy an aftermkt overdrive that bolts on where the carrier bearing is situated for a mere 3k but I was hoping someone might have a more, uh, creative solution. Perhaps there's a rear end out there that might include the bonus of improved braking along with a higher gear ratio. What about two speed axles??? Are they always geared low and lower???

Skip,
I consider only the late 47-53 and sometimes the 54 trucks as Advanced Design. Someone else may have more on this.

As for better gears for your truck.

You don't need a two speed, they are all really big and slow. With the exception of some rare and really old stuff that is probably not worth the money or effort.

You may want to look in to swapping a t-5 from an S-10 for the overdrive.

Start measuring vans you see in parking lots to see if the track with is the same or close to yours, then find a rear in a salvage yard for that van, it will probably have a 3.XX gear ratio if it is newer. I just sold a Dana 60 from an 80 something Ford 3/4 ton van. The axle flange to axle flange is 4" wider than a 52 Chevy 1 ton, perhaps exactly right for your truck??

Most any new axle can be easily adapted to disk brakes with a kit if you wish. Don't put disk on the rear unless you have them on the front.

Look into the Saturn overdrive that bolts on before your transmission, cost less than the gear vendors unit I think.

Taller tires help with the speed. My 52 1 ton fits some 8r19.5 tires that are 31" tall.

Decide how fast you want to go and at what engine RPM. Plug the numbers into this page and find what tire size, gear ratio, and overdrive ratio you need to do what you want. If you plan to work your truck don't gear it so fast that you can't start off with a load without burning the clutch.
http://www.4wheelparts.com/4wp/ORS/gear_calculator.asp
There is a better one out there but I can't find it right now.

Grigg

Here is the gear calculator I like.
http://www.drivetraindirect.com/t_gear_calculator.htm

Grigg

A '57 Chevy pickup is a Task Force truck, not an Advance Design.

GM used the same rear axle design on 3/4- and 1-ton trucks up to I think 1972. There are a couple of ratios available that might better fit your needs, including one real hard to find set that is about 3.70 (I don't recall the exact ratio).

I think the 3.whatever is most likely found in a later truck with a big block and an automatic, but I've never found one. The swap is pretty easy and can be accomplished in only hours according to some who have done it.

Task Force. Even better. OK, now that I'm up to speed, thanks for the tips. I think I've seen mention of the Saturn overdrive. I was led to believe it was a Jeep only device??? Can be made to work in any vehicle??? I've been so busy restoring this thing I haven't looked at the tires until you mentioned it. The fronts are 8R17.5 about 30" tall, the rears 7-17.5 29" tall. This probably helps to explain the bizarre handling characteristics of this E Ride and the funky way it sits (tad higher in front). The rubber is the only thing that was good on it when I bought it last October. So going big in back will be help lower the R's a little. Meanwhile, I look for a later model with a big block and automatic who is willing to give up his member. Is there a problem putting dually wheels on 3/4 ton van rear end???

Grigg, I looked into the Saturn overdrive. The site I looked at showed the unit being installed in a jeep transfer case. You saying there's a way to make it work in a GM four speed? You are right, it's a third the price of a gear vendors overdrve. It would be nice....

I think that the Saturn o/d is for Jeep/Scout 4x4 only. You may be thinking of the Ranger o/d that is made by the same company,Advance Adapters. The Ranger unit would be a good choice, you keep the 420 trans, the o/d unit mounts in front of your existing tranny. It moves it back about 7 inches. It works as a gear splitter, giving 8 forward and 2 reverse. I belive that they make them with different front and rear index bores/bolt patterns so they can be used to adapt later trannys as well.

Bill, Thanks for that. Interesting. I don't mean to sound dumb but I am. A 420 is the GM 4speed with the granny 1st that is currently is the truck? That would mean moving my shifter back on the floor then wouldn't it? (duhhh, lets see, 7 inches right? I'm not so dumb after all!) And because this is a dump truck I have a pto to contend with as well. I suppose I could just shorten the pto drive shaft right?....(appoximately 7 inches bubba!)

You are right, I was thinking about the Ranger overdrive that fits in front of the transmission.
The Saturn one is after..

No, I would not reccomend dual wheels on a semi floating axle. Could probably be done but I would only if it was a full floating one.

Yeah, I'm running a full floating now and any replacement would be that. Looking into truck salvage for a rear end or member. Overdrive a last, last resort.

I would suggest a Dana 70 as a swap, 8 lugs most of the time, good choice of gears up to 3.54.
Disk brakes available.
Often setup for dual wheels.
Good value for the money.
Take your time and shop around, take a tape measure.

Grigg, You are a genius. I went to a truck salvage togay and went thru their whole rack of rear ends. Very good learning experience. After about an hour the yard guy finally came over and talked to me. We found the rear end that is currently in my truck. He said "follow me" and took me over to where all the canabalized vehicles where up in the air. We ended up on an 88 Suburban with Dana 60 3.73 full float axle that was about as exact as can be in width and leaf mounts. $646.50 and I talked him into throwing in the driveshaft. Comes with a 90 day warranty. Will need adapter plate for duallys. To your knowledge, is there a problem with adapters???

Sounds like a suitable axle for your application.
But I am a bit confused, you say it is nearly the right width, and that you need adapters for the dual wheels?

Did your truck come stock with dual wheels? And is it really a 3/4 ton? If it were an AD model You could only get duals in 1 ton and larger...

You should be able to physicaly bolt dual wheels on without a problem even though it was intended for singles? However, the way the hub bearings are spaced in relation to the center of the wheels (load) may affect the life of the bearings if you switch to duals? This assuming the 60 you found has singles.
If it is a bolt pattern problem you have I would not use adapters, I would either find an axle with the pattern you need, or the wheels to fit the pattern you have, probably hard to find duals with fewer than 8 lugs.
Spring pearch spacing is easy enough to correct with some carefull measuring and welding. It should be exactly what the original was.
Driveshaft can probably be reused from original, length is proabbly exactly right and joint size too. In my 52 1 ton with a newer Dana 70 I had to shorten my shaft 1.375". The 60 is not quite as long as the 70 from center of yoke to center of axle, so you should be really close on the length of teh original shaft for working with a 60 axle. The Spicer U-joint size is 1350 on my 1 ton, and probably your 3/4 ton too. Dana 60 and 70 axles are most often equipped with 1350 size joints. New yokes can be purchased for about $65. I'll even have an extra when I switch my driveshaft to 1610 size joints soon.

Grigg,
I wasn't sure I bought what the guy was telling me about duallys not fitting but I didn't argue since I know nothing. I can't figure out a reason why they woudldn't just go right on. It's an eight bolt pattern. Stud length maybe but seems like you could just put longer studs in.

I'm really really confused about the tonnage of my truck. I was told it was a one ton when I bought it. I learned on this site that the 3600 is a 3/4 ton and that the 3800 is a one ton. The rear end in this thing is plenty beefy and it wouldn't surprise me it it's the same one for the 3800. I had 3900 lbs in it the other day. The suspension was definately overloaded.

As for driveshaft and ujoint stuff, that's another thing I know little about so I asked for the 'Burban drive shaft just in case. Then I figured I would sort it all out when I got it home. Need all the help I can get that's for sure.

Do your front wheels match the rear duals?
Do you want to keep dual wheels? If so, do they fit your new axle?

If all that works you have all the figguring done, just check your spring pearches and swap.

If you don't want duals, or want all 4 or 6 wheels to match and they don't now then there is still some more figguring to do....

After revewing your pictures...
I don't know enough about your, newer, non Advanced Design, truck to say if it is a 3/4 or 1 ton. Perhaps 1 ton?

I see that you will want to keep the wheels you have with the dual rears.

Assuming they fit the Dana 60 you found you are all set. If not then I would look for a 60 or 70 that has 8 lugs and came stock with dual wheels.

After thinking about it, I think you will be find using duals on what was a single axle. forget what I said earlier about the bearings and there placement, the load is sitll placed in the same relationship to them either single or dual. Anyone think otherwise, and why??

The Task Force 3/4 ton was available with dual wheels. On a '56, this option would include 7.00-17.5 6 ply tires and 10 leaf single stage springs.

That sounds right. No joy on that 'Burban rear end. I think the hub is too short. There's a little shoulder where the center of the wheel rides that is only deep enough for the one wheel. There may be other problems I don't know. I tried my wheels but the lugs were too fat.