Re: 637 V8 gas engine
 

That sounds like a Clark 5-Speed Trans. I had one in the '62 6500 and in my '67 7500. It liked it as I could go through 9 Gears and only have to downshift the Rear twice.

Re: 637 V8 gas engine
 

It is a 62 4000 with a 305 V6, wide fenders and very large front end. Was a brush rig for the local fire department here where I live. Has 15K original miles. 1000 gal water tank with Wisconsin engine driven water pump. The truck was originally a 2 wheel drive, converted at the dealer to 4x4.
I also have a 65 KV4000 with wide fenders and the same front end and transfer case.

Re: 637 V8 gas engine
 

Very true, very true. However, I was speaking from a repair standpoint, not a longevity standpoint. Dad's shop replaced a number of crankshafts in the Toro-flows while a GMC dealer for Georgia Highway express. They would not had to have been replaced if they had been Tocco-hardened. I have seen only 1 637, and it was in a steel tilt cab. The other 637 I only know from speaking to the owner at the time. When I look at the repairability of an engine, I look for things such as the design flaws, like the type of hardening on these shafts. I can't for my life understand why these crankshafts (gas & T-F 637 and T-F 478's) weren't tocco hardened.:banghead::banghead:

Re: 637 V8 gas engine
 

Bob, the D-cab was the aluminum cab (crackerbox).:thumbsup:

Re: 637 V8 gas engine
 

Road rangers of that era would more than likely been the RT-610 or RT-613 series transmission. These trannys are rated at 600 ft lbs of torque and were found behind many gas-engine trucks of all major brands of the day. This one looks like the RT600 series of Fuller transmission.:coolphotos::coolphotos::coolphotos:

Re: 637 V8 gas engine
 

Anybody know where to get a fuel pump for one?
Mine went out a few years ago and I ended up covering the hole with a plate and mounted an electric one on the frame.

Napa books all said discontinued.

Re: 637 V8 gas engine
 

Yes! I'm sure you are correct about them being a Clark. Dad took the Whole Darn Family sometimes, Mom rode Shotgun, my Sister and I traded between the sleeper bunk and sitting on the doghouse. The truck tended to jump out of 5th, and got "Tarp Strapped" into 5th so rolling hilly roads were driven like a roller coaster, just shifting the 2-speed.

Too bad GMC didn't Tocco harden the 478 & 637 crankshafts. International Harvester Tocco hardened crankshafts in the old Farmall H & M model farm tractors. Some just months away from 80 ( eighty ) years old are still running regularly with the original crankshaft. I've only ever seen ONE broken M crankshaft and heard of one other. Undersize main & rod bearings are NOT common in them.
Company I used to work for Nitrided lots of parts. Biggest advantage of Nitriding was the low temperature the process exposed the parts to, nitrided parts needed little if any finishing after nitriding. Depth of hardness was not real deep but deep enough. If crankshaft was reground nitriding would have to be redone.
Chrome plating crankshafts was common, but not used much anymore. On a stressed part like a crankshaft pealing the chrome off was a possibility. A plasma metal spray technique would be better, but enough heat is put into the crankshaft all the journals would have to be reground.

Re: 637 V8 gas engine
 

Right, I believe the RR in my '71 9500 (J-Model, Conventional Cab btw) was an RT-610.

Re: 637 V8 gas engine
 

Too bad GMC didn't Tocco harden the 478 & 637 crankshafts. International Harvester Tocco hardened crankshafts in the old Farmall H & M model farm tractors. Some just months away from 80 ( eighty ) years old are still running regularly with the original crankshaft. I've only ever seen ONE broken M crankshaft and heard of one other. Undersize main & rod bearings are NOT common in them.


I know GMC Tocco hardened 401 and 478 crankshafts back in the 60's, I have a factory shop manual that mentions it. In the 70's Tocco process was replaced with Tuftriding according to my factory parts manuals, they recommended after turning the cranks to have them Tuftrided, the posibility Diesel versions didn't have this process. When I had the crank turned on my 478 I told the machinist to have it tuftrided he told me that process was replace with Nitriding so that's what was done on my 478 crank:upyes:

Re: 637 V8 gas engine
 

Really!
No answer to a good question, on where to find a part for a 637?
The 637 replaced the Twin Six.
And no one has any advice on how to find a new fuel pump?
Do you even know where it is mounted on the 637?

Re: 637 V8 gas engine
 

2-Ton;

I've gotten some parts from EBay a few times and even went to NAPA and asked the Guy to look in his Old catalog stash as opposed to the computer. I've had several "New" pumps fail because I guess they were too old stock and the diaphragms would break.

Is the old one rebuild-able?

So in the end, I went with a Carter electric and no more problems.

https://www.summitracing.com/oh/part...4070/overview/

*PUMP LOCATION-I think some one mentioned the fuel pump is located on the top front of the engine mounted up with the arm pointing down looks like.

Re: 637 V8 gas engine
 

Thanks Funk
I did the same thing.
NAPA pulled the old hard copy out and showed me where it was discontinued years ago. Thought about taking the arm off and putting it on another pump.
But went with an electric pump.
The old pump is not rebuildable.

And yes, it is mounted on the front, top center of the engine with the 12 inch arm vertical.

Story of the truck here.
https://www.stovebolt.com/gallery/ki...on%201967.html

Don

Re: 637 V8 gas engine
 

I'm the one who has the running 637 on youtube. The pump you see on the engine is actually for a v6. I simply changed the arm like Two Ton suggested. I do have a couple of those pumps now if someone needs one. Not sure how long they sat on the shelf though.

Re: 637 V8 gas engine
 

I believe I put your video on the boards over at Heavy Haulers on the '67-'72 Chevy truck site. We have some 637 fans over there as well.

I'm also the one that used to drive a 637 V-8 Gas in a GMC J-9500. It was a '71 model with the very rare combo of a 10-Speed Road Ranger behind it.

Re: 637 V8 gas engine
 

I've never driven anything with a 637. I need to get this one I have into something. I'm going to try and get a HEI from a Buick 340 on it. I got some extra adapters from We7x.

Re: 637 V8 gas engine
 

You would need an HEI from a Buick 350, the 340 was long discontinued by the time the HEI was introduced.

Re: 637 V8 gas engine
 

You're probably right. I got one on Ebay that fits them all the way back to the 215. It was probably for a 350.