The Stovebolt Site Forums The Shop Area Engine Shop '57 3600 rear end saga

'57, 3600, duallys: The gearing is likely 4.57 or some such and I'm finding that I'm not the only one who finds that too low for even normal driving. So, for all of us, here's what I've learned so far. Higher aftermarket gears are not available although there seems to be some awareness that there is a market for them. They have the molds for them, they just haven't made a run and no one knows if they will. Don at Patricks in Az says he is working on that. A local driveline shop had an oldie like mine in their yard and broke it open. It was a 4.11 and he said the rebuild parts are pricey. $1200 to rebuild it and maybe use those 4.11 gears if they are any good. He claims that only $400 of that is labor, the rest being expensive bearings and such. Cost/benefit seems low. Maybe he's overcharging, I don't know. I met a guy there with a driveshaft business who told me to see his buddy with a truck salvage yard. Salvage guy said that my 52 1/2 inch backing plate to backing plate is quite small and suggested I go look thru his inventory. I plan on going there tomorrow and with any luck I'll find a late model rear end with full float axles, modern brakes and a gear ratio that will allow freeway driving. Otherwise it's plan C. Don't know what that will be. Perhaps engineering to alter a wider rear end? Anythings possible if you have the $$$$$$$.

There's another discussion of this from a different posting in big bolts but so many guys are interested in this subject that I thought I would create a stand alone posting for it. Today I went to a truck salvage and searched his rack of rears for the better part of an hour. The lot guy finally came and helped me. After showing him what was in the truck now he took me over to an 88 Suburban with a Dana 60 3.73 with full float axles. Not set up for duallys but I'm told an adapter is made for that. He got $646.50 and I got him to throw in the drive shaft. The shocks looked new and he said he'd leave those on too although don't know if they will be useful. It even has a 90 day warranty. His fork lift was broken so I go pick it up on Wed. I'll be looking for those adapters in the meantime. More $$$$$$.I hope there's not a problem with adapters.

Dana 60? In an '88 'Burban? I think that it may actually be a 14 bolt GM corporate full floater.
I don't think that GM used Dana axles in their trucks in the '80s for the rear. Either way, it'll be plenty stout. I beleive that the only difference for a dually rear on a GM is wheel stud lenght, I've never seen any type of adapter on dual wheel American trucks, regardless of brand. The last dually I saw with an adapter was a Toyota, and it was an aftermarket conversion. Some sort of motor home thing, I remember the owner wanting the cheapest tires for it.

Bill, Thanks for that info. I'm learning as I go and have learned to double check the things I'm told. I wasn't going to argue with the guy since I know less than just about everybody. 3.73 was crayoned on the thing and that's my main concern. I did the measurements of the width and the spring mounts myself which is good. The salvage yard fellow who told me it was a Dana made himself sound like an expert. On the other hand, he did smell of alcohol and it was 10AM.

Backing palte to backing plate measurement is not of much importance on a rear axle so long as the springs fit between them.

It is important to have the same wheel mounting surface to wheel mounting surface measurement, or be prepared to find or have made wheels to make it fit you intended application. This measurement is best taken with a tape measure, a helper, and two straight edges.

Educate yourself on the differences between a dana axle and the rest of them.

Don't spend your money till you understand all the info that you can find on the part you intend to buy. Be your own expert. Don't trust any salesman, including a drunk one at the junk yard. Do your homework and buy what you need for the reasons that matter to you, not what the salesman thinks are your needs.

On another note, the price quoted for the axle you are looking at sounds high to me. I am only 3,000 miles away, and that may make a difference, but $300 to $400 would be top dollar to me, $250 sounds very reasonable.
Check eBay for past auctions, ones that actually sold, that is a good indicator of fair price.

Grigg

GM used a lot of Dana axles on their van,s. Either one are stought. I prefer the GM corp. rear end. They are easier to work on. I agree with Longbox if you put in longer studs the duals will fit but the brakes are smaller.

I think I will take two wheels off the truck and take them with me when I go pick up the rear end. I'll need rollers on it anyways and I can see exactly if they will fit or not. If not I guess I can back out of the deal. I have no knowledge of what constitutes a fair price for a used rear end. In Southern California there are few salvage yards due to environmental and the high value of land. So it could be a matter of supply and demand of the local mkt. Thanks for the tips. I'll check around.

Grigg, You were so right and I'm so dummm. I got online and found carparts.com, entered my zip and got a huge list of salvage places in my area. Suburban rear ends went from $250 to $400!!!! Man was I getting reamed or what?????

I have a Dana 70 I'm told came out from under a 80's Chevy 1-ton (Diesel). I never saw the rest of the truck, so all I know is what the axle looks like.

I also have a couple of 14-bolt GM rears and since some of these are loose I have been watching prices. I see them on craigslist for $250 to $750 all the time. I'd expect you could get one easily in the $200-$300 range with a little patience.

One of my 14-bolts is mounted under a '50 Chevy 1-ton frame. I bought it that way, so don't know what it took to do it, but it looks like it fits there real well.

I'm a little rattled today. I gave the salvage guy a check last Saturday for the 'Burban rear end. I was to pick it up on Wed. So, I'm on jury duty today but called him on a break to discuss the price after I found out he was charging me two or three times the going price. The guy mad dogged me. Called me an unflattering name, said his brother is an attorney, should have done my homework, blah, blah, blah. Made the first cut on a murder trial. No kidding. I go back tommorrow for the first real day of jury selection. Do you think I can use the excuse that I can't serve because my truck needs to get restored???

Anyways, I got out of there a little early so I stopped payment on the check and went to another place. They were helpful. Let me try my wheels on the 'Burban rear end (priced at $300). The hub appears to be too short with a little shoulder that is only deep enough for the one wheel. I'm thinking that wheel centers need to ride on that shoulder. In any event, the lugs were too fat for my wheel to go on.

I may have made anther blunder. I bought a rear end off a Chevy 3500 one ton dually, that I thought might work for $450. We opened it up and found 12 41 on the gear. Makes it a 3.43??? I knew it was a tad narrower but I thought I could make it work. When I got home it seems I didn't take into account the amount of space taken up by the inner dually wheel and I think the thing is going to be too narrow to work. I bought some huge 19 inch wheels for fifty bucks each including some good tires. I'm going to try those to see if the taller tires lower my gear ratio.

No kidding, a murder trial. With lying in wait. It's been a strange day.

Tough day in court. Jury selection continues at a glacier pace. On the way home, I decided I would try out the 19.5 inch wheels I bought yesterday. The lug holes are larger than the lugs on this thing but I decided it won't hurt to bolt the duallys up tight and try them. They are much larger than the 17.5's that were on there and it raised the overall tire height from 29 to 33 inches.

I took it for a test drive. Took off in 2nd gear no problem. Don't have a tach so I can't be scientific about this but it's much quieter at cruising speed of 45 to 50mph. At 55 it's not screaming like it was and I feel I have much more left. Got up to 65 momentarily and while the engine had plenty more, the truck is beyond it's technological ability to go fast. I've never ridden one but it's like what I imagine galluping on a camel would be.

For those of you who know more than me, (that's all y'all), I ask: Are there potential problems with running these giant 19,5's on my little 3600 dually? How might I rectify the problem of the lugs being smaller than the holes???

I'm a little confused. How did you know how fast you were going?

The taller tires effectively change the ratio, but unless you've adjusted the speedometer for that change you are really going quite a bit faster than the indicated speed (provided the speedometer was right before).

The improvement noise wise might be quieter tires instead of the motor going slower. It may be that new tires all around might be all you really need.

What kind of tires did you take off?

Once I know these wheels are keepers I will likely buy new. The truck came with new 17.5 inch Yokahama radials on the front. The four rears are old cracked Highway tires however with lots of tread.

Speedo was pretty accurate if you trust those highway speed signs. How much faster would you estimate, was I going at say, 50mph??????

Looks like at 50 indicated you were doing about 57.
Speed

Skip,

There are hub piloted rims and lug piloted rims. The ones on your 20 year old small car are lug piloted (i.e. the lug nuts have a tapered section that aligns the rim to center on the hub). Big trucks are hub piloted. Which is to say that there is a fine fit between the hub and the center of the rim. These lug nuts are flat on the inside and simply hold the rim against the hub but don't align the rim in any way.

My 1958 3800 dually has 19.5" rims. They are hub piloted. The lugs fit snug through the lug holes in the rim. The rim center fits snug to the hub. When torquing the 8 lug nuts down to ~100 ft lbs it makes your rims and hubs a one piece structure capable of with standing severe side loading you might encounter hauling a load around a corner.

Now you say you had 17.5's and are looking to change to 19.5's. The clearance should not be a problem (front to back), but you might have to lift your truck an inch or two to get top to bottom clearance. If you never plan on carrying a load then don't bother.

I am concerned about your large stud holes on the rim and small studs. You likely have 1/2" studs but your rims are made for 9/16 studs (I'm just making an educated guess here). This is NOT a good situation. Once again, carrying no load and driving around the block is probably no problem, but if you carry 2 tons of gravel 500 miles on a windy road... that could spell disaster.

You can either find some spacers and put them on your studs, but a 1/32" thick spacer will not last for long. Or you can have some spacers welded onto your rims. Or you can drill out your hubs and drums for the 9/16" studs. This will require more effort, but is perhaps the best idea. You'll have to get the drilling done at a machine shop. You'll have to remove your hub/drum combo (easy on these full floater axles). Take it to a shop and have them press out the old studs. Then have them drill for 9/16 studs and install them onto the hub / drum. While you have it apart you might consider getting some new wheel bearings and possibly brake shoes.

My $0.02.

Everyone's $0.02 is worth the crown jewels to this old truck boy.

Just think, at 50mph, I was smokin' down the road at nearly 60mph!!!! And at 65, I was going at close to... mach one!!!!!

Very good explanation of lug/hub piloted wheels and explains how the wheels become integral to the hub. I would think that this could help explain why it's not a good idea to force the issue by putting dually wheels on a hub designed for just the one, something I had contemplated doing with the 'Burban rear end.

Had not considered clearance. Not a problem empty but fully loaded???. The leafs are close to the tires. Brakes have been redone and plan to upgrade if possible down the road. (upgraded brakes and some kind of power assist to the extent that these things are possible).

I thought of making spacers but pictured them being a very weak solution. I do like the one of replacing the studs. Cheap insurance.

You guys are the best...

One thing you might look into is cross referencing the studs at the flaps. They should have a wheel stud book that gives the dimensions of the studs. You should be able to find 9/16" studs that have the same knurl (spined part) as the original 1/2" studs. It won't hurt if they are a few thousandths larger, they'll just fit tighter. You can install new studs easily your self using a nut and a stack of washers. You use the nut to pull the stud in with the threads, the washers act as a spacer and a thrust surface. There is also a tool available for about $35, but for a one time use the nut/washer deal will be fine. I did the same thing on my 3200 to change from 7/16" studs to 1/2" studs.

Roger that. Will look into it. Thanks Bill!

Your rear should be hub piloted. ?
use this page to help you with figuring speeds and gears and tire size.
http://www.drivetraindirect.com/t_gear_calculator.htm

I looked at the chart...33 inch tire with a 4.56 rear end at 65mph is whirlin' at over 3 grand. I decoded the engine by way of a book and block numbers. It has a mid 70's, 350 truck motor. What is a good highway cruising RPM?????

listen to someone who knows small blocks, but to get you started I would guess 2,000 to 2,300 is a happy cruising speed.

You don't say how you want to use this truck. If you are going to haul heavy loads with it I would not be too concerned about spinning a 350 at 3000 running down the freeway.

With an HEI (started in pickups in '75 I think) they will turn way past 5000 and they have a good pressure oiling system and a valve mechanism that can handle turning fast.

2000 to 2300 is fine for a light empty pickup.

My 1-ton pickup with 4.11 gears and 31 inch tires runs down the road just fine at 75 or 80 even pulling a trailer. At 65 its turning about 2900 at 75 its about 3300.

Empty thats a bit of a waste, but loaded I appreciate the power it makes turning faster, and this isn't a 350 its a 454.

The smaller your motor or bigger your load the more important gearing is to performance.

From what you've said I wonder if chasing a ratio change is the right place to start. You may want to spend more time determining why its noisy and riding like a camel. It may be the ratio change isn't going to fix the problem, but will eat up some serious money.

Yes, hub piloted. And I will be installing the larger studs to accomodate the big wheels. Very good information guys. I do learn alot each time I get feedback and I hope others with this issue are reading this as well.

It won't see heavy daily use. Original plan was to use it on my little acre property 200 miles from here where it would just sit most of the time. However, I have become attached to it so I now want to keep it here for occasional use (a load of stone for a friend) and drive it when I go up there. That's why I need to make it more freeway friendly, (take the strain off the driver and the motor.)

The motor has good compression. Installed an electronic distributor and rebuilt the quadrajet, new exhaust system, sound deadening material inside the cab. Driveline work has been done. With the addition of the 19.5 inch wheels, the noise is greatly reduced and the R's have been lowered considerably. I don't mind driving 50 to 55 MPH to keep the R's down. Using the calculator that Grigg referred me to that would mean RPM's in the 2500 range. Before the big tires, the R's were about 2800 and it was quite a bit louder. I have decided I don't want to change out the whole rear end. I will keep looking for a 4.11 member. Hope springs eternal.

It is a galluping camel. You can't sip an nice cup of coffee whilst driving this thing unless you want to take a chance on wearing it or running off the road if you know what I mean. So, steering and suspension are the next projects.

Some day you guys are going to rule the world!!!! Old trucks everywhere!!!!