The Stovebolt Site Forums The Parking Lot Big Bolts Building my diesel Franken' Truck

I've brainstormed quite a bit and figured my cheapest/most unique non- CDL way to go is to use stuff I've got laying around the farm. So what I have is a 48 GMC 1.5 ton (no engine) and a 79 Chevy C70 diesel with a 4-53T Detroit/5 speed tranny with 70,000 miles. I was wondering if I could use The Detroit, the C70 rear axle and my original frame? With the C70 rear axle (2 speed) would I still be able to use it with no CDL license? Feel free to give other ideas, tell me what will work and what won't, but keep in mind this is a low budget operation. This project won't be in action for at least another year. Also would my original 3 row radiator be sufficient for cooling this engine?

No CDL needed to drive a truck that has a GVW of less than 26.001 pounds. So if you move the C70 driveline to your 48 GMC you're good to go.

Mike B

Sounds like a GREAT swap! That later model axle should get you up to 60 M.P.H.,if not a little more. Some others more familiar with this swap,can inform you of clearance issues,as well as motor mounts,and such. Good-Luck,Keep us posted,and Happy Holidays!

Axle from a C-70 is pretty huge. I feel you'd be better off with something smaller and with faster gears for a 1.5 or 2 ton truck. Perhaps a Dana 70HD or an 80.

Radiator should be sufficient for the 4-53T.

The axle in a C70 would probably be an 18,500 Eaton. You will almost need to keep the 2 speed behind the 5 speed, and I don't think you will find a better ratio than what your truck was born with. It was probably a 5.29/7.20 or a 4.86/6.86. It depends on which 5 speed you have. If you have a close ratio 4th and 5th, it will have the wide ratio Eaton. If you have a wider ratio 4th and 5th, you will have the closer ratio 2 speed. You will need at least 10 speeds for the little 4-53T and a 5 and 2 is the most practical way to get 10 speeds. The frame width of your 1 1/2 to n should be the same as the C70. I

Grigg, I was thinking the same thing when I looked at the axle. I thought " Holy S#$t that pumpkin has to be 20" tall". I have a few questions about your Detroit build, I couldn't find your post about it. What were the major mods you had to do, radiator relocation? fire wall? front axle/ oil pan clearance? inner fender wall cutting?

The 48 1.5 ton rear frame is 36" outside, the C70 ought to be 34", not the same. A 400 series GMC would have a 34" rear frame, but not the smaller trucks.

My own build thread is quite old, bad picture links... this project has taken a long time and then life got in the way, so still not done. https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=752661&page=1

Here are a fair amount of pictures of my project. https://picasaweb.google.com/118082...ictures02?authuser=0&feat=directlink
I did have to modify the firewall, mostly widen the indentation to fit around the wide Detroit cylinder head. Also needed to make a little room over the flywheel housing so later the transmission can be removed without removing the cab. Aditionally I used a 3" body lift.
The radiator is in stock location (except 3" higher). Inner fenders may or may not need trimming, not sure yet.

The GMC turns out to be a little easier to swap because more room between radiator and cab.
Here are some pictures of a friend's truck that I was able to start the conversion on. Also turned out the GMC front engine mount crossmember if holes are enlarged from oval to round fit perfectly with the Detroit 4-53 front engine mount from GM truck like yours and positions the engine well in the available space.
https://picasaweb.google.com/118082...dranger02?authuser=0&feat=directlink

Grigg

I didn't realize that the 1 1/2 ton trucks had a 36" frame. Moving the spring seats an inch on each side shouldn't be a problem. If you can squeeze the motor in, getting the rear to fit should be no problem. However, you didn't mention. Does the 70 series have air brakes. If it does, it would be a problem. Unless you go all out and put air disc on the steering axle, it wouldn't really work. However, the Eaton 3rd member will fit in a hydraulic brake banjo housing out of a fire truck. RT series Fullers did OK on vocational trucks, but they have such a big gap between 9th and 10th gear that you have to wait for a down hill stretch to get into 10th gear. Detroits almost need a 13 speed to be drivable on the highway with a single speed rear.

The little dump truck in this picture was had a Detroit with a 5 and 2 and would up in a similar project to what you are doing.

https://plus.google.com/10819770718...5975870034&oid=108197707187186692269

A few years ago I bought, drove a lot, and later sold a 61 F350 with a 6V53T and Roadranger RTO-610 transmisison, 0.80 OD ratio. It was a very nice combination, about 400-500 RPM drops in all gears when shifting from about 2,300-2,400 RPM. It made some serious torque after 1,800 RPM so was very comfortable to drive in and out of 9th and 10th gear, not a large step. Most I hauled with it was between 20,000 and 30,000 lb total truck and all for a couple thousand miles, OD was less used then, but available on the moderate down hills. https://picasaweb.google.com/lh/photo/zqtbm_-eztH-KxNHD8O4rdMTjNZETYmyPJy0liipFm0?feat=directlink

Unless you use it commercially you don't need a CDL no matter how big it is.

But as others have said unless you are rated over 26,000 you aren't commercial anyway.

I don't have a CDL and so far no state I've lived in has required one. (Ohio, Georgia, New York, Virginia) They have exceptions for non-commercial/recreational use.
Tad

Thanks everybody for the pictures, it always makes work easier to have a visual helper. And to answer crenwelge's question, I have seen the model 70 in air or juice brakes, this one happens to be the juice. Isn't it nice when a dream falls together!?!?

Due to the Detroit being fairly heavy will I need to upgrade/change my front suspension?

If it is a 1 1/2 ton, I am assuming it is a 300 series. They had a pretty good front axle. The springs were made to haul part of the load. If your springs are in good condition, it should be no problem.

I agree.
The 6cyl is not a light engine either. The 4-53T weighs more, but only a few hundred more.

Does anyone have any pics on trucks with Dayton wheels in the rear and budd type on front? I don't know how bad or good it will look with that combination.

I ran my entire fleet with Budds on the steering and Dayton on the drivers from the 60's until the mid 90's. I switched to hub piloted because outboard drums are not possible on Daytons. This was a very common practice. Schneider National ran thousands of cabover Internationals that came from the factory with Budd on the steer and Dayton on the drivers. Before outboard drums became common, stud piloted or what we called Budds were a real pain. Wheels would crack between the holes and studs would break and you had to pull the whole hub. Daytons can stand a lot more twisting and are still specced on severe service trucks like garbage trucks.

I have a similar setup to Grigg's in my '37 GMC. What wheel bolt pattern do you have now? If 5/10, then a D-70 or 80 come with that pattern. 22.5" tubeless wheels are available, however, hard to find. Fit and Look correct in the fenders.

You want about 3:1 final drive ratio if you wanted drive on the freeway, plan how to achieve that from the start.

Good luck.

Yeah Ed I have 5 on the front and 10 on the back, but I wont need to be going any faster than 55mph for local driving. My plan is to have a decent looking/ reliable/ cool sounding truck to take to shows and light farm work.