Tomorrow I am picking up a 1956 GMC 370 LCF that was a factory Coleman 4x4 conversion. The cab it pretty good but it has some weird stuff done to it and some holes cut out... I want to put the 4x4 axles under my 59 Spartan. are the leaf perches in the same place? does anyone know? I am not sure what chevy size the 370 cross references over to but from what I can tell the frame on my 59 could be .12" wider. What I am wondering is did they change the perches on the axles to make up the difference or is it in the hangars?
.12" is less than 1/8 ". Even if the perches on the axles are off by the 1/8:, there should be that much play on the spring pack. If that is all they are off by, you should be able to just bolt it on.
The F-370 has a standard GVW of 19,500 pounds and optional up to 22,000 pounds which puts it on the fence between a 5000 Series 2 ton and 7,000 Series 2-1/2 ton.
Your '59 100 with Cast Spoke wheels is more than likely rated at 25,000 pounds GVW, so swapping axles will be a GVW down grade.
FYI, Low Cab Forward (LCF) is a Chevrolet thing, GMC just called that style the "F" Series.
Cuda, I am aware that it's only eighth of an inch. Seems like just forcing it over isn't the correct thing to do though. However I've never done this before. I'm not familiar with tolerances with things like this.
Mike, thanks for the clarification on the cab name.
I'm was thinking it might be a downgrade but the tag on my truck actually says 19.5k so I guess it'll probably be the same. I'm never gonna get near it anyway so I'm not too worried.
It's actually got a straight 6. I haven't pulled the number yet but I think it might be a 426.
And it is a pretty dang nice truck. Not really any rust, but I don't have the bandwidth to work on a second rig. I was gonna take what I need and offer the rest up here on the bolt.
Who made the 4x4 drive line, Marmon-Harrington or NAPCO? Is anything broken in the 4x4 driveline, parts may be made of unobtainum.
As soon as you pull the axles, transfer case, linkage and cross member it will be basically be scrap, as it will be very hard and expensive to move what's left.
Check the rear brake sizes...the GMC could be 15 x 4 while the Chevy is 16.5 x 5.5.
What are the gear ratios of both trucks? You could be going from slow to slower...
The GMC will have a 15,000# Corporate rear and the Chevy will have a 18,000# Eaton rear.
Mike it was a Howe-Coleman conversion. Do you know on most of those conversions did they replace just the front axle or both? I thought they needed to be a matched set. The front diff and hubs have Coleman cast into them so I know the front axle is theirs.
Also everything is complete and in working order.
I don't know the gear ratios because I haven't pulled the info off the axle tags yet. Hopefully tomorrow. I also don't plan on going anywhere fast. That's why I drive a 1959 truck. If I need speed I hop on the Buell 😉
If the gears are too low, one could add a Brownie, if there is enough driveline length, remember to use it only in 2wd. That engine could also be a 302.
Ed
Last edited by EdPruss; 03/18/201911:32 AM.
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
I think you need to spend some quality time comparing the two trucks front hubs to see if there is room for the Air Brake hardware on the back of the Backing Plate on the H-C axle. I think the knuckle takes up a lot of real-estate and you may be stuck with using the Hydraulic Brakes it came with.
Normally the truck was ordered knowing it was going to be up-fitted with a 4x4 front axle by a third party vendor, so they ordered it with the correct rear axle ratio from the start to save money.
