1949 chevy 3100 rear end questions

[ryans69chevy]

hey, my dad and i are working on a 1949 chevy 3100 1/2 ton (or so we think). It was used as a grain truck on my great grandpas farm and nobody really seems to know much more than that about it. the front end has a 6 bold pattern where the back end has an 8 bolt. the rear end is jacked up so high also prob so the extra weight wouldn't effect it.

were wondering what rear end from what other vehicles we could get to fit under this pickup without any modifications? we want something that can do good on the highway since we aren't planning on towing anything with it.

Thanks!

[raycow]

It sounds like a PO swapped in a 3/4 or 1 ton rear at some point. You probably wouldn't enjoy the gearing at highway speeds.

A few questions first. What kind of transmission does it have? When you look at the driveshaft how many U-joints can you see? Is all of the driveshaft exposed, or is any part of it enclosed in a tube so you can't see it turn?

Ray

[Steve@OldSub.com]

Originally Posted by ryans69chevy

were wondering what rear end from what other vehicles we could get to fit under this pickup without any modifications?

Can you post some pictures of how the rear axle is mounted. Somebody make some modifications to mount an 8-lug rear under the truck and suggesting a swap that does not require modification requires knowing what it looks like now.

Is the axle above or below the springs? Has the frame been modified?

If it still has the stock frame and springs you may be able to convert back to a stock type rear without too much trouble.

[ryans69chevy]

here is some of the pics i took ill post some more here in a min if i can. the tranny we believe is a 4 speed, it was originally a 3-on the tree not sure why they changed it. when we got the truck it still had the 3-on the tree "workings" as well as under the hood. as far as i can see there is nothing around the driveshaft i got some pics of it and how weirdly angled the thing is...i don't know if thats how it is suppose to be or not...

[ryans69chevy]

here is the rest of the pics of the rear end. i also took some of the inside of the cab. My dad and i are taking all the rust off and putting on POR 15 to protect the metal against future rust. I also have pics of the 216 cubic inch 6volt motor also if anyone wants to see those ill post them. hopefully someone can help us find a rear end that we could take out of some vehicle and put under this truck without any modifications if posible. thanks!

[T Hilde]

Yes, that is a 1/2 ton frame. Loose the axle and the overloads and keep the main spring pack and you should be back to a 3100. Are you wanting to restore this or ??? Because you will have a number of options available to you for the rear axle.

[ryans69chevy]

yes we want to restore this. we are actually in the process of that right now. we are prob gonna have the cab off by the end of the week. we want to have this thing be a good runner on the highway so maybe somewhere around a 3.08?? or what were you thinking as some of the options? we always like ideas! thanks

[raycow]

Originally Posted by ryans69chevy

the tranny we believe is a 4 speed, it was originally a 3-on the tree not sure why they changed it. when we got the truck it still had the 3-on the tree "workings" as well as under the hood. as far as i can see there is nothing around the driveshaft i got some pics of it and how weirdly angled the thing is...i don't know if thats how it is suppose to be or not...

The transmission swap was a necessary part of the open drive conversion because the original 3 speed was set up for a torque tube. If you would rather have the shifter back on the column you could use a 55-67 3 speed.

It looks like the PO swapped in the complete driveline from a later 3/4 ton and shortened the rear driveshaft to fit the 1/2 ton WB. It's actually not a bad job, other than the angle on the middle and rear U-joints. You could help the angle by lowering the rear of the truck or going to a one-piece shaft.

Your best bet for a rear end would be one from a 63-69 1/2 ton. This would get you 6 lugs and better gearing while remaining approximately the same width as stock. Check 4WD Chevy rears or any GMC rears first, as they are already set up for leaf springs. You might have to re-locate the spring pads to match your stock spring spacing. Most 2WD Chevy rears in those years are coil spring, so those would need spring pads welded on anyway.

Ray

[T Hilde]

Originally Posted by raycow

Your best bet for a rear end would be one from a 63-69 1/2 ton. This would get you 6 lugs and better gearing while remaining approximately the same width as stock. Check 4WD Chevy rears or any GMC rears first, as they are already set up for leaf springs. You might have to re-locate the spring pads to match your stock spring spacing. Most 2WD Chevy rears in those years are coil spring, so those would need spring pads welded on anyway.

Ray

Also look to the '73 and up 4X4, they were six lug also.

[ryans69chevy]

Originally Posted by raycow

The transmission swap was a necessary part of the open drive conversion because the original 3 speed was set up for a torque tube. If you would rather have the shifter back on the column you could use a 55-67 3 speed.

It looks like the PO swapped in the complete driveline from a later 3/4 ton and shortened the rear driveshaft to fit the 1/2 ton WB. It's actually not a bad job, other than the angle on the middle and rear U-joints. You could help the angle by lowering the rear of the truck or going to a one-piece shaft.

Your best bet for a rear end would be one from a 63-69 1/2 ton. This would get you 6 lugs and better gearing while remaining approximately the same width as stock. Check 4WD Chevy rears or any GMC rears first, as they are already set up for leaf springs. You might have to re-locate the spring pads to match your stock spring spacing. Most 2WD Chevy rears in those years are coil spring, so those would need spring pads welded on anyway.

Ray

ya, it looks pretty good. i'm not sure if my great grandpa did the work himself or had someone else do it for him. But he has owned the thing from the beginning. we are going to change it up anyway. we want a 1/2 ton rear end. i actually own a 69 chevy c10 1/2 ton. I'm in the process of finding a rear end for this as well. So if i find 2 rear ends at a junk yard with around a 3.08 ratio I'm buying them! I have a couple questions on the driveshafts tho...

First of all could i get a rear end for the 49 from a 70-72 c10? Because 67-72 were all the same pretty much. I'm just trying to get a bigger window here so i can find a rear end easier. Ill try and get one that had leaf springs. If i was to get a rear end from a c10 1/2 ton would i need to get a driveshaft custom made to fit the 49? or could i take the driveshaft that i got the rear end from. I'm sure it will have a 2 piece driveshaft. and FINALLY...i want to get a rear end that i know has good gears still...so how do i know if they are good or not??

Thanks for all the help!

[mr48chev]

71/72 C 10's have 5 lug patterns. Later 4x4 rear ends may be a bit wide for the truck.
I have put a 56 rear end under a 53 3100 by using a set of aftermarket spring pads.

From looking at the photos it appears that they may have just added the helper springs on top along with installing the 8 lug rear end although they may have also used 3/4 ton springs.

What I would do is find the rear end that I wanted to run, pull out the 8 lug rear end and helper springs and install the new rearend in the proper place on top of the springs with new U bolts. Buy U bolts long enough so that you can install lowering blocks if needed or trim off the excess if you don't need the length but that will save buying U bolts twice. Put the truck together and drive it a bit and see what the stance looks like and go from there. You could probably get by with running the 4 speed and drive shaft that is in the truck now for the time being if the truck runs until you decide what you want to do. If you switch to a column shift three speed I'd suggest the later full syncro trans from the mid sixties. I have had one in my 48 for years and it is a lot nicer to drive than the older ones.

[raycow]

Originally Posted by ryans69chevy

First of all could i get a rear end for the 49 from a 70-72 c10? Because 67-72 were all the same pretty much. I'm just trying to get a bigger window here so i can find a rear end easier. Ill try and get one that had leaf springs. If i was to get a rear end from a c10 1/2 ton would i need to get a driveshaft custom made to fit the 49? or could i take the driveshaft that i got the rear end from. I'm sure it will have a 2 piece driveshaft. and FINALLY...i want to get a rear end that i know has good gears still...so how do i know if they are good or not??

71-up rears (and some 70) are about 1-1/2" wider than stock. They will work, but you may have fender clearance issues if you run wide tires/wheels, especially if you are lowered.

I'm not sure what later stock driveshafts will fit without modification. If you look at newer trucks, the engine sits farther forward relative to the front wheels than yours does. This means that even if you find one with the same wheelbase as yours, the shaft may be too long for your truck. You best bet is to get everything bolted together first, measure for the shaft length you need, and then head for the salvage yard with your tape. I have had very good luck finding shafts that way, and have needed a custom shaft for less than 10% of my swaps

Buying a used rear is always somewhat of a crapshoot, although I have never personally gotten burned. Naturally you will want to take off the cover and inspect for obvious damage, but this doesn't neccessarily guarantee that it will run quietly. Fortunately, most honest salvage yards will give you some kind of exchange guarantee.


Ray

[raycow]

You will want to get some rear shocks on there if you are going to be driving the truck on the street. As you can see, the stock shock links have been removed, probably when the rear end was swapped. If you can find or make the links, there are outfits that rebuild those lever shocks for people doing stock restos. However, it will cost less to change over to the tubular type, and they are probably a better choice for a driver.

Ray

[ryans69chevy]

Originally Posted by raycow

71-up rears (and some 70) are about 1-1/2" wider than stock. They will work, but you may have fender clearance issues if you run wide tires/wheels, especially if you are lowered.

I'm not sure what later stock driveshafts will fit without modification. If you look at newer trucks, the engine sits farther forward relative to the front wheels than yours does. This means that even if you find one with the same wheelbase as yours, the shaft may be too long for your truck. You best bet is to get everything bolted together first, measure for the shaft length you need, and then head for the salvage yard with your tape. I have had very good luck finding shafts that way, and have needed a custom shaft for less than 10% of my swaps

Buying a used rear is always somewhat of a crapshoot, although I have never personally gotten burned. Naturally you will want to take off the cover and inspect for obvious damage, but this doesn't neccessarily guarantee that it will run quietly. Fortunately, most honest salvage yards will give you some kind of exchange guarantee.


Ray

Thanks for all the great info! It's making our job somewhat easier and so we aren't b-s-ing our way through this, although it is pretty fun to do esp when everything goes the way you want it too! I guess since we are attempting to totally restore this puppy buying a rear end from a salvage yard will have to wait for a little longer than we expected since we should bolt it up and drive it to make sure everything is alright.

We plan to go through the engine pretty good. Since you seem to be a genius in the rear ends do you have any advice for us as far as going through the motor. It's a pretty broad question, but this is gonna be the first time myself or my dad have gone internally into a motor so we want to make sure we do everything right. It's a 216, we have manually turned it over and it turned freely, but we haven't started it yet because it's filled with lots of gunk! I guess in the early 90's one of my cousins had this thing running for a school project, but we believe it hasn't run since then. I don't know if this is relevant but we plan on converting to a 12 volt system.

Again thanks for all the help!

[ryans69chevy]

Here is a pic of the 216. We have taken off the water pump so nothing is actually missing if anyone caught that from the pic.

[raycow]

If you are going to tear into the engine, most of the procedure is fairly straightforward, but it has a few peculiarities you won't find on modern engines. Before starting disassembly, definitely get yourself a shop manual if you are going to be doing anything more invasive than removing the valve cover.

To get the bellhousing off you must remove the flywheel first. Four of the bellhousing bolts are behind the flywheel. The timing cover is also unusual in that the bottom two bolts go through from the inside. You must remove the oil pan to get to them. It was fairly common practice on teardowns to helicoil the holes in the front main bearing cap and drill out the threads in the cover so the bolts could be re-installed from the outside. This procedure was not authorized by GM, but it saves some work if the timing gears subsequently need servicing.

Probably the oddest thing about the engine is the connecting rod oiling system. The rod journals are not drilled and fed from the mains as in most engines. Instead, the rod cap has a hole in it and a small scoop is attached undeneath. This scoop passes through a kind of tray affair which you wil see when you remove the pan. Be very careful when handling the tray, because it contains nozzles which are supposed to be aimed at the scoops. If the nozzles get bent out of place the oil stream will miss the scoop and the rod bearings will starve for oil. GM used to supply a special tool for aligning the nozzles, but I have no clue where you would find one of those today.

The rods to not have normal bearing inserts, but rather a cast-in-place babbit bearing which is machined to a specified diameter. Final adjustment of the bearing clearance is done with shims between the cap and rod. Aftermarket re-manufactured rods used to be offered which accepted insert type bearings to avoid having to diddle with the shims, but I don't know if those are still available. I believe there are outfits which can still re-babbit the stock rods if you are intent on doing a totally stock resto on the engine.

A lot of people building a driver will replace the 216 with a later 235 which has full-pressure oiling to the rods and no scoops, shims, etc. The 235 is practically a bolt-in, which makes the swap very easy. However, the 216 can provide very dependable transportation if you pay attention to its oddities and do something about the stock gearing.

On passenger cars, the 3.55 gears from a powerglide rear were a bolt-in swap and enabled the car to be driven reliably at highway speeds. Unfortunately, this swap does not work on the AD trucks, so Patrick's (and maybe others) offer 3.55 gears for the stock truck rear. These gears won't work for you because your original torque tube rear has already been replaced. Actually, open drive is really a better option anyway, because it gives you a wider choice of ratios and costs less than the Patrick's gears.

Ray