The Stovebolt Site Forums The Shop Area Driveline '40 rear end ???

I've posted in the General forum and the Engine forum about the truck I just got delivered. I'm still going through it to see what I've got and trying to decide which way I want to go with the build. I was originally going to do a daily driver restoration and keep it as original as possible. I knew the rear end had been switched but so far I can't figure out with what. I've attached some photos of what's under the truck and could use some help identifying it and suggestions for replacing it.

At some point someone put a 5 lug unit in. It also appears to have heavy duty springs since the original, from what I've seen had 7 leaves and this one has 10. It's also an open drive unit. They also removed the emergency brake lines and handle from the cab. The rear shocks have also been disconnected for some reason. I've attached some photos that I've taken so far.

I've located a complete '40 drive line with a complete closed drive shaft and rear end with the wheels and emergency brake lines. There's no handle so I'd still have to locate that. I've also found a '51 complete drive line, which is much closer to where I live. Question #1 is the '51 and '40 drive line basically the same? Will the '51 fit the '40 truck? #2 would I be better off just switching it out for something else, Camaro, Nova, Ford 9" etc.? I plan on just using the truck to drive back and forth to Home Depot and maybe take it to a few car shows when it's done. I doubt it will ever see a freeway.

Joe

Here are some additional photos from under the truck. The last one shows the position of the wheel in relation to the fender.

I am not sure this would work Joe, but I have heard that if you flip the leaf springs around your tire may be centered in the wheel well.

This problem has to do with swapping different year axles on trucks and passenger cars alike. I may need to do that when I swap the '55 Series 2 rear axle on my '46.

This is a passenger car, but you'll get the idea, same hold true for trucks.

Hey T,

I'll have to check the measurements between the axle and the mounting positions. If it does move the axle back I'll have to see how far out it pulls the drive shaft from the trans. But it's worth a shot.

Thanks,
Joe

I've seen this fix the same problem on trucks also. I'm pretty certain if it doesn't help 100%, it will help most of it. The ones I've seen get really close to center in most cases. I think it is worth measuring and/or trying if it looks right.

Finally got out to measure the spring/axle distances. From the front spring shackle to the center of the axle is 27", from the rear it's 25" so reversing it would only bring it closer to the front of the rear fender. Like I said, I don't know what year (or for that matter make) the rear end is but I know the fenders are wrong. As I said in some posts in other sections I'm going to get it in the garage take all the body off and decide what to do. I'm leaning toward a 283/327 swap with a Mustang II front and some 4 link rear. Maybe a T5 and some rear end with a 3.73 or lower final drive. I've read here somewhere that Nova or Camaro rear ends will work with the '40 frame.

Joe

If I was going to put a V8 in mine it would be a 327, best SBC and first fuel injected engine to be built. The 283 is it's little brother, probably gets better gas mileage, but less power. But I'm keeping the 235 that was put into it before I got it.


Your frame should be like mine, I have a '46, which was the same as the '41, and I'm pretty sure there isn't much different on yours sans the grill and light differences.

I found a '55 Series 2 rear axle and using it so I can reuse my wheels. If you plan on getting new wheels, those camero and nova rears typically have 5 lug 4.75" diam pattern on them.

S10 will work well in your truck also, most likely the 2WD, the 4WD is about 4" wider and people use those for the AD trucks, but those truck are also 4" wide fender to fender. Another I've seen both rear axles and front clips is from a corvette. And if you get lucky on one of those it will have disc brakes, probably not as useful on the rears, but couldn't hurt if you plan to get with disc brakes on the front as well.

Hi T,

I'm going to do a compression check on the 235 as soon as I get time and see what readings I get. My original thought was to keep it as original as I could, but given that the drive line has already been replaced I was thinking the V8 swap might not be a bad idea. It looks like some work has been done to the 235. I see new fittings on some of the lines, the carb has obviously been rebuilt so I'm still trying to see what my options are. There are a few 327s I've found on Craigslist that look promising.

I'm definitely going to be taking it all apart, including removing the cab, since I will have to replace the floor under the gas tank/seat riser. The bed is going to be replaced too. That will allow me to box the frame which will give me the option for more power.

It's already got the 5 lug wheels on the back and 6 lug original wheels on the front. I was thinking about going with a 5 lug set up so I could use Cragers or American Racing 5 spoke wheels. Something about those that I just like the look of. So I guess once I get the body off I'll be able to see exactly what the prior owner put in the rear. It looks like a 10 bolt but that about all I've figured out so far. I have no idea about the year, ratio or if it's a posi or not. The trans is a 4 speed but I'm not sure what kind yet. The Muncie they used in '53 should have a closed drive line, but this one is open. I guess it's one of those things I'm going to have to wait until I get all the panels off to see what it is. I've attached a photo of the top of it trans.

I was thinking about doing a Build Post in that section and posting photos as I progress.

Joe

JoeR, your plans sound very interesting. What is the year and model? There are many times that I wish I would have done what you are planning regarding an older mixed up truck. The 327 really got my attention (my all time favorite), Crager chromes, oh my gosh had several sets on various rods. You need to contact some of the bolters about your other questions but. it would definitely be advantageous to put a 5 lug on the back. 4 Cragers are max. Good luck and go for it. I'm the odd man out of the group because I have always had great luck with 9 bolt Ford rear ends. As for the tranny mine is out of a 1940 3/4 ton Chevy truck, great trans. for the farm or an all stock restoration the number on mine is K96 L. There are many links on Stovebolt to match up what you have. Good luck and have fun. I have probably saved ten of thousands of dollars on shrinks by just working on my old cars and trucks. Hey I may be crazy but I sure get along fine with everyone on this site. Doc

Got the floor board off and took these photos of the transmission. I'm still not sure what I'm looking at.

Looks like a Chevrolet 4 speed transmission, with original bell housing with the pedals mounted to the bell housing.

This transmission doesn't have synchros on any of the gears, AFAIK.

Hi Doc,

I know what you mean regarding the therapeutic nature of what we do, lol. Plus we keep those great trucks on the road! I restore old wood working equipment too, so I've got a double dose of sanity. I think.

Regarding the transmission, as Trad said, it looks like an original GM 4 speed, but shouldn't it have a closed drive line? Is it possible to remove the torque tube without changing everything else?

The rear has 5 lug, it's the front that has the original wheels with 6 lugs. But I'm seriously considering one of those Mustang II front ends, which will give me the 5 lugs. As far as the rear goes I guess I'll have to wait until I take everything apart to see exactly what rear end is there. I had a '64 1/2 Mustang convertible that I put a set of Cragers on, looked perfect.

I'm looking forward to pulling it into the garage, pulling all the sheet metal off and seeing which way I"ll go.

Joe

Hey T,

As I wrote to Doc's message, shouldn't there be a torque tube if this is from a '53 Chevy? I thought the open drive line didn't start until '55? I'm thinking the prior owner sort of grabbed a piece from here and a piece from there, like the Johnny Cash song said, lol.

Joe

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Did I do something wrong?

No Joe, it wasn’t you. All is well, carry on!

Whew!

So it looks to be a SM420 4 speed transmission. I'm not sure if that is going to work if I go with a 327 up front. I may have to locate a T5. I'm going to see if I can get the truck into the garage this week and put it up on jack stands and scrape off the gunk on the rear end and see if I can locate any casting numbers or some how identify it. I'll also turn the wheels and see what the ratio is. Maybe pull the cover off and have a look inside. After looking at the outline of the old fenders on the bed side panels I'm thinking it's the '47 fenders that are the problem since the outline of the '40 fenders is a good 2" further forward, which would give the wheels the room then need.

The other part that is missing is the emergency brake and the lines. The pulleys are on the frame but I'm guessing when they replaced the engine/trans/rear they pulled the brake and just never replaced it.

Joe

The easy fix to just make a local driver would be to swap that 4 speed out to a 3 speed of the same vintage. The 3 speed would have 2nd, and 3rd gears synchronized. That would get you back to a stock six bolt axle torque tube if that is the direction you want to go. That unique master cylinder bracket should still fit. Once you start down the other path it will be a money pit in my opinion. If you drop in a v8 well then you will have to upgrade the brakes, then you will have to upgrade the steering, then you will have to upgrade the suspension, then the wiring, interior, 3 point seatbelts, door latches, etc... The list will be long, and possibly never get done. Which would be frustrating.

That 4 speed could be out of a 3/4 ton long bed pickup. I believe they had a 2 piece drive line with a carrier bearing.

Art

A 420 trans will work fine with a 327, however high gear is direct. T-5’s high gear is some sort of OD, depending on gears. A T-5 will not withstand a lot of heavy loads, rough driving.

Ed

had a 420 behind a 350hp 327 in my '63 1/2 ton with 3.73 rear. It was pretty sweet setup. 1st was no longer granny, but still didnt use much. No overdrive, but neither di the old camaros, chargers and mustangs. Upper three gears were all synchro. I'm with Ed. the T5 out of s10 is lighter duty but there are other t5 options.

The fenders look like they came off a AD truck (47-53). If you change back to the ‘40 fenders, the wheel centering problem may go away!

Hi Art,

That's the decision I'm trying to make, go as original as possible or modify it. I'm making a list of all the things I'll need to do the upgrade. As you said, suspension, frame boxing, wiring etc. There are several Mustang II packages that include the cross member, suspension, including disc brakes and steering. I was planning on getting a wiring harness anyway since what's in there now is just about 100' for red 14 gauge that runs everywhere. I'm just going to see what the bottom line is and go from there. I'm not going to be putting in some monster LS motor with 600 hp, I'm thinking something like a simple 327 with a Holley or I've just found a Fenton intake with 3 deuces that would look pretty cool under the hood.

Joe

Hi Phil,

Yeah, they're definitely post '47 rear fenders. I've located a set of pre '47s and I think that should solve the issue. I can see where the correct fenders mount and it's about 2 inches forward of where these are so that will give me plenty of room.

Joe

Hey Larry,

I'm hearing that the 420 is a pretty bulletproof trans. Unfortunately mine isn't going into reverse. I'm thinking something isn't meshing in there so I'll be taking the top off this weekend and having a look. I'm not too concerned about an O/D gear since I don't plan on doing any freeway driving with it, just back and forth to Home Depot and a car show or 2.

Joe

Novak in SLC has all the parts and diagrams for a 420 you will need.

Ed

If you are looking for a 6 lug axle check out the Colorado rear ends. There are 2 different widths. 1 is 63.5 inches wide and 1 is 60 inches wide. the 60 inch is the 1 i will be using in my 40.

Joe

4wd is the wider one.

Ed

The Colorado came with a choice of 3.42, 3.73 and 4.11 gears. There is also the limited slip that was offered on the four wheel drives and anything with a towing package.