The Stovebolt Site Forums The Shop Area Driveline Rear end swap advice requested--1957 GMC one ton panel

I recently purchased a '57 GMC one ton panel. It has the Spicer rear end with the very low gear ratio, I'm assuming somewhere in the low 5's. Since I can't change the Spicer gears (at least I don't think I can...please let me know if I am incorrect), I will install a different rear end.

I have an Eaton HO52 with 4.10 gears that I can install, but I'd rather get a gear ratio in the mid to high 3's.

I want to keep the 8 lugs and large drum brakes.

I have read other posts that there are some direct swap rear ends (e.g. mid 90's Dodge heavy vans) that will meet my needs. Anyone have any advice about what I should be looking for?

An ideal set-up would be a direct swap, 3.55 ratio, use the same 8 lug rims, large drums and limited slip. The limited slip would be nice, but not necessary.

Thanks for your help,

Matt

Might be a D-60, check on the diff. casting for a cast number, 51, 60, 70, 71, etc., that will be a start, then you can see what gears are available.

Ed

Ed, thanks. The Dana 60 looks like it would be a good swap.

I found a GM 14 bolt 3.73 Posi from a '94 Suburban 3/4 ton. Rough wms-wms measurement indicates that it will fit. Before I go crawling around under the truck to get more accurate measurements, anyone have any experience swapping out for one of these?

Thanks,

Matt

Cant you change the carrier and ring and pinion in a Spicer?

FF 14 bolts are a good alternative, cheap, plentiful, might be less work for a novice gear changer, IF, measures up right, otherwise easy to change gears.

Ed

It is my understanding, perhaps incorrectly, that there aren't any options with tall enough gears for the Spicers that came with these trucks. If I am wrong, I'd love to be corrected because I'd rather do as jmoore suggests.

East Coast Gear Supply lists a 3.54 ring and pinion for a Spicer/Dana 60. I don't know anything in regards to compatibility.

Did you look at your diff. casting and find the diff. number so we know what rear end we are talking about?

Ed

The older Spicer differentials have different pinion offset (below ring gear centerline) and new gears don't fit the old housings. Not sure what year the change?
I had a 65 F350 and ran into this problem, I think it was 0.5" offset for the old one and 5/8" for modern ones. I was not able to find faster gears I wanted and swapped the entire axle.

Ed, I was thinking the exact same thing when I read jmoore's last post. I haven't had the truck delivered yet because the old tires are rotted and the new ones that I ordered haven't arrived yet. I am going to pay a visit to the truck during the week and will get the casting numbers.

I looked at some pictures that I took under the truck and the rear end might not be original. It has shock mounts welded to bottom of both sides of the axle (no shocks, though) which makes me think that it might be a later model. I'm pretty sure that if it was original, the lower shock mounts would have been separate brackets attached to the spring ubolts under the axle bracket.

I will get the casting numbers. I also plan to jack it up to see if it is an open or limited slip differential and I'll estimate the ratio by counting the tire/driveshaft revolutions.

Matt

Numbers should be at the corners of the casting. Good luck.

Ed

I visited the truck today and checked a few things. The axle is a non-posi Dana 60 with a 4.10 ratio and a C-30255 casting number.

I don't think that it is original to the truck because of the shock mounts welded to the bottom of the axle that I mentioned earlier.

Maybe I'm in for a pleasant surprise? Is this one a good candidate for replacing the gears?

In the short term, I can certainly live with the 4.10 gears. That in itself was a pleasant surprise.

Now if it had only been a posi...

Thoughts?

Thanks,

Matt

It is easy to put up to 3.54 gears plus posi in there, depending on your engine and use.

Ed

Ed, thanks. The 3.54 gears are very reasonable, too, compared to the kits for the 1/2 ton pickups. My plan is to switch to the 3.54 gears, but leave it as an open differential. The posi idea was a nice to have, not a need to have.

Thanks again,

Matt

FWIW
Chase at East Coast claims their gear set will fit.
Possible need to change the yoke if pinion spline count is different.

My 59 Burb is running a limited slip Dana 60 3/4 ton full-floater. I'm using a mid-1970's GMC housing with a 3.73 Ford ring and pinion and a Dodge pinion flange. Some International applications ran the same setup, so a pretty wide variety of parts will swap around to get what you want.
Jerry

Thanks to everyone for all of the input.

I got lucky and found a NOS Dana (not a knock off) 3.54 ring and pinion for the rear end on one of my junkyard picks. Someone had bought them, never installed them, and I found them in a parts truck with a few other goodies. I haven't installed it yet.

I'm trying to get most of my parts assembled before I begin on the panel later this summer.

Matt