The Stovebolt Site Forums Project Journals Project Journals 1941 GMC COE on a modern frame

Comment by Moderator: Please join us in giving a massive and sincere "Stovebolt" welcome to the newest member of our Project Journal forum, Dave “Homer52”!

We are absolutely thrilled to have Dave join our Project Journal forum and can't wait to follow along with his incredible project. Dave is embarking on the ambitious undertaking of transplanting a 1941 GMC COE onto a 2001 Chevy 3500 cutaway van chassis. And to make things even more interesting and unique, he's planning to mount the engine behind the cab! This is a build that promises to be a true testament to ingenuity and skill, and we're so excited to witness it unfold.

It's abundantly clear that Dave’s passion for GM trucks runs deep. He's already got a fantastic collection in his stable, including a peaceful 1941 GMC, a completed 1946/1947 Chevy street rod sitting on an S10 frame, a 1945 GMC panel truck, and a 1941 Chevy COE with an as-yet-undetermined destiny. With this kind of history, we know he's bringing a wealth of experience and dedication to his new project.

While Dave initially started his journal in the HiPo forum, his build is so exceptionally unique, and we're so impressed by the skills he'll undoubtedly employ to overcome the challenges this transformation will present, that we knew he absolutely had to be featured here in the Project Journal forum.

Welcome aboard, Dave “Homer52”! We're all incredibly excited to see your 1941 GMC COE project come to life.

Here’s the start of Dave’s journal:

Just sitting on blocks getting an idea how things will fit. Dave.

Looking nice. What is the frame from?

2001 chevy 3500 cutaway van.

Very solid looking truck!

Here are more pictures of my project, the fittings in question are from the transmission to the radiator, from the engine to the radiator for oil cooling, also the power steering.

I don’t believe I can use stock hoses and tubing because of the long runs to the middle of the truck.


Another question, by moving the engine to behind the cab I have taken so much weight off the front end it has affected the alignment and I will have to change coil springs or shorten the existing springs. I have to come up with some sort of tool to remove and replace those coil springs. I know I have to use caution!

So it's not going to be a Cab OVER Engine anymore. But I suppose if you did do that the cab would be a LOT higher than it was on the old chassis. You were talking in another thread about framing around the engine on the cab floor. Did the engine width make that not doable? I assume that mid engine location is going to be a lot lower than shown in your third pic. Unless you're talking a V-drive like a boat would use.
Alaska Rubber could fab longer hoses for you, especially for the power steering. Probably a hydraulic shop in Homer as well. You'd probably need to bring your wheelbarrow of cash along. Steel tubing could be used for the tranny cooler lines, probably the PS lines as well.

The fittings are easy and you have several options.

1. You can buy adapters to go to a standard hose: https://a.co/d/4zprzNJ

They are ugly and stick out a long way, but work.

2. The stock hard lines have nice bends where they come out and run parallel to the frame. You can cut those off and flare the ends to an AN fitting and get AN soft (or hard) lines to reach where you need to go.

3. The fitting in the transmission and the radiator will unscrew because they are NPT inserts. You can remove those and replace them with whatever NPT fittings you like.

Personally, I like to go with Option #2. The stock hardlines are nice and tight and it is really convenient to be able to quickly disconnect them.

The suspension question is more complicated. Let me think on that one a bit. Autozone will loan you a compressor tool. I have seen a few lowering kits for that vintage truck that might work, but let me cross-reference the van 3500 against the other availavle suspension types before I lead you down the wrong path.

The fittings

I think I would wait until the front suspension is loaded with everything finished, you'll have some weight up front just due to the cab being further forward. The mid engine location is still gonna' have some of the weight on the front end.

Good thought! I have a lot of planning to do.

The power steering fittings in your last picture are M16x1.5 metric o-rings.

You can do the same trick where you cut them off and flare them for your preferred fitting or you can get an adapter to inverted flare here.

I agree with 78Buckshot, the weight on the front end will probably be the least of your issues, I can't wait to see the finished product!

When I move the engine behind the cab should I install a crossmember right at the motor mount location? I will be moving the tailshaft cross member.

This is fascinating exchange here. Gonna move it over to Hi-Po, as a better spot for even more!

Are you shortening the frame for the more blunt nose on the COE?

Yes, today I cut the front frame off just forward of the sway bar fittings. I put the front grill hood and one fender on, things look pretty good, front wheel seems to be centered in the wheelwell.. I think I may cut some off the rear of the frame also, I don’t know what I will be doing behind the cab yet.

Do you think I should have a cross member right where the motor mounts will be? Dave

The photobucket link in your thread does not work for me. Your build is unique and really interesting to me and other ‘bolters. As the Moderator of the Project Journal forum, I’m looking at your build as a possible submission to the Journals. One of the requirements is to eliminate photo links, as so many links over the years have been broken losing the pictures associated with the post.

May I suggest using the Attachment Manager to post your pictures. You can now post up to ten per post. If you need help with attaching the pictures, there is a link on the left margin explaining the process. If you still need hep, I can assist.

I was waiting to hear about cutting the frame before commenting on this. You want to maintain comparable stiffness to the unmodified version.

You want to make sure that you keep the frame sufficiently stiff across the front suspension to make sure it doesn't shift under heavy cornering.

Looking at the GM Upfitter Guide there is a big crossmember in front of the axle. Did you keep that? If not, you will definitely want to put in a heavy duty crossmember in the front section.

All I cut off was about 4-5" forward of the sway bar. All existing cross members are still there with the exception of the tailshaft cross member which I will reinstall.

Do you have a picture of the frame? What I can't tell from the documentation is if there is a crossmember between the control arm mounts or not.

Looking online, it appears that it has a crossmember that the engine mounted above. It is hard to tell the truck vs van frames apart in those pictures though.

This photo shows it but not great. Yes, there is a cross member between the control arms.The engine mounts sits on the aft portion of this cross member. Just let me know what photos you need and I will get them.. Dave

Some more photos for reference.

If you keep the crossmember that the engine was bolted to, you should be fine.

If you are pulling that one out for some reason, you will need to stabilize the front end.

My plan is to leave the front crossmember as is, i will still have to deal with the coil springs. Dave

I concur with other recommendations that you wait on tinkering with the springs/airbags until you get the engine and cab mounted where you want them and can measure what change you want with it fully loaded.

I think my path now will be to get the cab positioned on the frame so I can build a subframe to support the cab. After that I think I should position the engine and get the driveline set. Then on to body work.

The spec from GM is that the lower control arm should be level with the ground when sitting at full weight on a level surface.

You can pull the spring out and put blocks under the control arms to get them into that location for eyeballing where you want the fenders to end up relative to the tires.

Then when you have your weight/distribution figured out you can figure out what you need to do spring-wise to get the steering geometry correct.

Edit: with the springs out, you could run a ratchet strap around the frame to hold the control arm instead of blocks. That would let you lift and lower the frame without needing to re-set the stands under the control arms.

I now see I need to amend my procedure. I should remove sheetmetal from the frame, reinstall engine so I have some weight on the coils, remove the coils, then remove engine, position lower control arms, then install sheetmetal to get proper stance. After all that I can move engine to behind the cab and do all body work knowing when complete I will have proper stance before getting the geometry where it needs to be. Wow that was a mouthful, hope I'm thinking correctly.

I am not sure you need the engine weight to take the coils out. A spring compressor should do the job just fine.

I would recommend getting the cab location correct before mounting the engine, that way you can adjust the engine location to where it is convenient for the cab instead of having to modify the cab for where the engine ended up.

I feel like where it is sitting right now is + or - 1 inch horizontally from where it needs to be it's just the vertical I'm not sure of. I was thinking if I had the engine sitting in the original position I could remove the upper control arm, shock , swaybar and steering linkage and then lift the frame to release tension on the spring. I am going to call OReillys and see if they have a spring compressor.

Do *not* try to take it apart that way. That is a great way to turn the spring into a rocket. If you are lucky it won't remove your arm or something worse.

A spring compressor is the right way. Any of your FLAPS should have one.

I will do it that way, I don’t like petting a snake. I am out of commission for a few days., had a big lump taken off my chest, way more than I thought, about 2 hours of cutting. Got home and I started bleeding, had to go back tonight and get it redone.

Homer just hang in there.

Pulled a rear brake drum today, what a PITA, after all was said and done i found the problem was a stuck emergency brake on that side. Also drained the differential by pulling the cover, did not find the drain plug until after, good thing, there was metal on the magnet, some big chunks. See no damage to ring or pinion! Guess I will now have to dig deeper, I have no history on this truck, maybe previous damage but don't think I can take a chance.

Here are the instructions from GM for how to measure the front suspension height. They say to replace parts if it is out of spec, but with what you are doing, I think you could trim your springs to get where you want to be.

Let me know if you need a zoomed in version or something.

Edit: I find it easier to measure from the ground up to the specified datums and subtract them rather than trying to measure from one to the other.

Pulled the coils yesterday, today was a short day but using wooden blocks I got Z to 4.5 inches, need fine tuning now.

Here is the diagram closer. Not a lot more detailed, but somewhat better.

Also some warnings and assembly instructions to go with it.

The torque spec is 101ft-lb (137N-m).

Here are pictures of the ball joint.

Based on the diagram, I think this is the spot that it means.

Dove into the differential today, found the damage, glad I tore it apart! Herei is what I found, now to fix it.

That's not ideal. I am planning to tear into my diff tomorrow. Hopefully it is less borked.

I have a replacement carrier on order, will be here in 6 to 8 weeks.

I have in the past few days boxed portions of the frame behind the cab where the engine mounts and the trans tailshaft mount sit.

Sounds like you are continuing to make good progress. Did you get the new crossmembers put in?

I did a LOT of calculating, i have plumb bobs hanging and i installed the crossmember for the transmission tailshaft in place and will make the final welds when i install the engine/transmission and confirm my calculations were correct. Right now it is bolted in place, the center section can still pivot until I weld . I have been doing small sheetmetal rust repairs because I didn't get any 18 0r 20 guage. Alaska steel was out, will go to Morgan steel next time. Borrowed my friends sheetmetal brake which will help a bit. Dave

mmm...sheet metal

Sounds like you have it all under control. It will be exciting to see how it turns out.

The yukon locker carrier arrived, now I am cleaning up the entire diff, there are metal fillings in everything and it has been a big job getting it clean. Soon to start the assembly then on to final adjustments. Dave

Are you going to put in new wheel bearings/seals while you are in there? It might be a good time.

Yes, everything will be new.

The new carrier went in today. I was very lucky, I just got the ring gear in place after sitting the carrier outside in -5 temps for 2 hours and heating the ring gear lightly with my heat gun when my friend walked in and helped me install and torque the bolts. Now to adjust backlash and wear pattern.

For the 2 previous days I worked at my neighbors place, he had a stroke and we installed an elevator because he lives upstairs in his aircraft hanger. He has lived up there for about 4 years, then fell and broke hip and paralyzed leg. In assisted right now but determined to get back home. I described him to some as fiercely independent, his good friend said not correct, that is no where strong enough language. By the way all these years he was using a spiral staircase, I don't know how.

I enjoy reading about your project COE. Much respect for your skills.

Well, I have recovered enough from covid to get back to work. Yesterday I spent most of the day building a spanner wrench for adjusting the backlash, I ordered one but it was too wide to fit in the gap. It would have been much easier to just have the commercial tool work, no such luck. I got the backlash set and the wear pattern is good also. I'm glad that is out of the way. Not knowing what the gear ratio was I checked and it must be 4.10 or close.Dave

4.11 was one of the more common ratios in those axles, so it is likely that.

Good to hear that you are recovering!

Engine and trans went in today, the tailshaft is bolted up, the front end is still hanging on the hook with blocking in case the hoist slips. When I boxed in the frame I left about 4 inches hanging below the frame but the lower 2 holes fall right at the frame channel, I will have to weld an extra plate onto them to basically raise and lower the mounting bolts about 3/4 inch.

Today I finished welding the floor in, went well.

Firewall is now bent up and installed, very solid.

I'm following,looks great so far ! I have the twin to your COE but, am looking at using a 95 Chevy 3500HD frame with mid or front LS engine.

In the past few days I temporarily put the seats in and got them drilled and bolted in place. I got the steering column from the cutaway and put it in temporarily, I saw it had potential so I cut a 6x6 inch hole in the firewall and with its 2 universals I connected it to the steering gear, it looks like it will work just fine, now to engineer mounting structures for it.

Today I did some testing, the seat felt a bit low so I propped it up on 2x lumber. It was much better I may go with 2 inch square steel. I am going to use remote hydro boost, I think it will work nicely. About to order an electric emergency brake kit, it should make for more room in the cab.

Pulled the cab off again, need to finish welding subframe and build a frame for the gas tank.

Working on the gas tank install today, part way there, will try to finish tomorrow.

Look at what followed me home today! It is a 41 gmc coe, cab, doors, fenders and grille only. It is in WAY better shape than my chevy and I may have to change direction. If I changed directions it would only set me back maybe 2 days but put me ahead months, it's that much better shape.

First pic is at home, second is at the top of turnagain pass.

Nice find.

Convenient that it fits in the back of your pickup. Makes transport a lot easier.

That's not only a funny picture, that is a GREAT caption. Gonna snag it for future use.

I did a lot of measuring and planning, it went in with about an inch to spare, I had to put it up on 2 pallets to clear the wheel wells. I knew the old gmc and chevy truck were very close to the same but with differences, I have been finding more differances today, the most notable is it appears gmc did not use clutch head screws in 1941, they used Phillips heads. Maybe not all gmcs, my 41 pickup has clutch head screws, will have. Tolook at my 45.

I started on the gmc coe in the last 2 weeks. CHEVY CAB OFF, Gmc cab on. The doors were very ill fitting, I tried lots of things and finally put the doors on in the correct position without the hinge pins in. I then could see the misalignment in the hinges and got out the torch and heated and bent them. I also have the floor and firewall cut out, fitted the floor and need to have the firewall piece bent up. It will cover the firewall angle down to the floor then angle to lay flat to the floor. Made up all of the cab mounts and fit them to the subframe.

I put all the sheet metal together today just to see if it will work together, what do you think? Can you tell what I have done?

Looks good, Dave
Except for the Chevy Grille.

Looks good!

Looks good IMHO too! Only question I would ask at this point is have you cycled the front wheels full swing left and right to make sure the tires clear the fenders. Don't forget to allow for clearance for possible body roll when the truck is in turns that may close up a possibly too small gap.

Just got word that my parts that I had at the chrome shop are on the way home. Will be a long time before I need them. Yes, I did cycle the wheels.

What shop did your chroming?

Are you going with the Chevy lower grille? It looks pretty straight. I wouldn't have known you installed that except I checked the pic I took of your Chevy COE from when we first met. I guess also because it was red.

The big give away when finished will be the fenders, they are gmc and have the headlights in the fenders instead of on top as in chevy. I will post where I had the chrome done after I see them, hopefully in a week.

With this rig being mid-engine, I would think it would actually handle quite well. A COE isn't the kind of rig you'd think of taking sharp corners in, but this looks like all the weight is down quite low. I bet it will drive really nice through the turns.

I got my chromed parts today, at this point they look beautiful, time will tell how they hold up. Some were very pitted and now look perfect.



Done by

Red's Parts Attic
23220 Laura
New Caney Texas 77357-9236

You can check them out on the web.

Dave

Where's the pics of your chromed stuff?? We'd like to drool over it.

OK OK! It is REALLY DIFFICULT to take good pictures of chrome and I am NOT a good photographer.

I had to throw in the Chevy hood emblem that was done by art brass in Seattle (no longer doing automotive)
The gmc will be sporting chevy bright works. Dave

Ok, you're right about it being hard to take good pics of chrome. I think the best way would be outside with a nice blue sky reflected in them. But that's still some good looking stuff. I think they'll look great when installed. Thanks for the pics.
[on edit] Dave, Here are some good tips for photos of chrome.

I started removing body filler, what a mess, the person who did this must have bought filler in a 5 gallon bucket. I heat with a propane torch and scrape off with a wood chiesel. When I get it hot enough it comes off nice. I have the passenger fender done and 1/3 of the driver side. The passenger side photo has a 4 pound hammer laying in the debris pile. The metal underneath is pretty good, I don't understand the massive amount of body filler.