VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 36 High Speed Diff

Bloo,

The 1936 Pontiac 8 was rated at 162 ft-lb torque and the 1940 Chevrolet truck 216 motor was rated at 168 ft-lb.

Both my 37 and 40 Chev pickups had their original 216 engines (rebuilt) when I installed the 3.55 gear sets in them, but I've since installed a 261 Chev 6 engine in the 1940 pickup. Now that is the perfect drive train combination. Plenty of reserve torque at 65 mph and probably capable of 85 mph or more, though I never drive over 70 mph (except when passing) because it just doesn't feel safe with the original suspension, steering and brakes.

When I rebuilt the Pontiac 8 motor, I installed .030 over aluminum pistons, and, with the 4.11 rear end, the engine was turning over at about 3250 rpm at 65 mph. I was quite confident that the motor could sustain that speed all day long, and, in fact, it did on many occasions until the deer collision.

The 1936 Pontiac 8 cylinder engine had a 3/8" shorter stroke than the 6 cylinder, and the crankshaft of the 8 was actually lighter than the 6, enabling a higher rpm red line than the six. The actual horsepower and torque differences between the two motors was pretty minimal.

Good luck with your project this winter.

Mark

I do not know the torque of his 6 Cyl. 208 C.I. engine but in my estimation a 4.11 would be about all it could handle on all but level ground. There was a reason they used a stock 4.4 ratio to give adquate performance.

Well, I guess we are going to find out. Their priorities certainly weren't the same as the priorities of modern drivers.

I have often wondered if it is a weaker engine than a Chevrolet 207 (the Pontiac is a flathead), or if the engineers just thought it could handle RPM better because of the full pressure lower end. They probably didn't want it to feel weaker than a Chevrolet in high gear, as it cost a little more.

It looks from the performance curves in the Pontiac manual, and in Buick manuals I have seen from the era, that the engineers were designing for what they thought was best use of the horsepower available, in other words maximum horsepower occurring at what might be the practical limit for speed.

It also seems that the measure of a good car in those days was how well it can pull hills in high gear without downshifting.

One thing the Pontiac manual does say is (paraphasing because I don't have the manual handy) "studies have shown most drivers drive about 30 or 35 miles per hour".

I do know that Buick Special gears are 4.44, and nearly every owner is clamoring for something higher these days. That is a more powerful car then my Pontiac, yet still 4.44.

Today, if you have a car that likes to go 35 or 40 MPH, it feels like you are going to get run over. I doubt that was an issue in the 1930s, or even something the engineers thought about. The wide smooth roads were still a few years away.

If this could do a relaxed 50mph, that would be much better. I'll find out this winter...

Bumping this old thread because I am back on the project again. The only thing I was missing was a decent differential case.

I got a whole 36 Chevy 1/2 ton rearend from a forum member here (Thanks, Darwin!) and took it apart yesterday. It is different inside than what I expected. The parts do not match the rear axles I have so far.

The first big obvious difference is that this one is full of bronze bushings. The differential pinions are bushed on the shaft, and they have bronze thrust washers behind them. The side gears have bronze thrust washers beside them as well.

The differential pinion shaft size is 0.746" and the shaft is stamped 1772555 (the other 36's are more like 0.800).

The differential pinions have 12 teeth, are bushed in bronze with a 0.747" ID, and are stamped 1760740 (other 36's here are 10 teeth with an unbushed 0.805" hole).

The differential side gears have 18 teeth and are 1.684" where they drop into the hole in the differential case. They have a 1.260 major diameter on the splines. No part number is visible.(other 36 gears here are 1.783" where they drop into the case and have a 1.250 major diameter on the splines).

The differential case is very hard to read for the part number, but is probably 1782860. The side bearings are New Departure 0103.(Other 36's here have a`case marked 369951 and use New Departure 0100 bearings).

Ring gear is marked 1769899 10-41, and is riveted on, as expected. Ring gear ID is about 5.63" (it is 5.42 of the Chev Master & Pontiac stuff I have here).

I couldn't find part numbers even close to these in the books on oldcarmanualproject. The axle is probably Canadian.

What on earth am I looking at?

1936 is way different than 1937. Improvements in engineering where coming fast. Since the 1920's and into the 1930's Chevrolet was moving forward every six (6) months with improvements (changing engineering) and going back and improving on their older models, too. So you could get an improved head and carburetor set for an older engine to improve horse power in a year or two after your purchase. This made Chevrolet a good investment as they were taking care of their customers. There are even differences in Early and Late 1936 Chevrolets. That is why 1937 will not fit 1936 and looks so different.

This axle came supposedly from a 1936 pickup. I saw the cab, and it looked like a 1936 low cab to me. None of these internal parts match the parts books. The parts should interchange all the way up to 1939 1/2 ton if one believes the manual.

This uses the same side bearings as a standard, but is a slightly larger diff than a master. The axle shafts are slightly bigger too.

It seems odd that they would tool up and build a whole different axle for a few trucks in Canada. I guess it must have come from somewhere else at GM. The only likely suspect is the 1936 40 series Buick, a one year oddball that is similar but slightly larger than Chevrolet Master. Those Buick axles were all 4.44. This is 41-10, so more like what you would expect in a Chevrolet.

I wonder if it could be GMC?

Does it have a torque tube?

Yes it has a torque tube. And 6 lug flanges on the axles. I have not measured the torque tube yet, but will today.

Oh, yeah, it has Huck brakes.

Torque tube (and punkin) length is 60 1/2" from the gasket surface to the end of the torque tube. The u-joint spline sticks on out to 62"

The diameter of the surface where the packing nut would tighten, at the front of the torque tube is 1 3/4".

Look At 1936 Master parts list.

1936 Master is what this should match but doesn't. Literally none of the major parts fit. Close, but no cigar. The part numbers are also way off.

I was hoping to identify this axle in case someone, somewhere could use it. It needs bearings, but the gears look to be in fine shape.

I will keep looking for yet another axle to get a 364538 (cast 369951) differential case out of. That is the only part I still need to start assembling my project.

I checked Buick part numbers from 1934-1940 and they do not match.
I would suspect it was a Canadian "Special".

That sounds right. Check Buick parts list or other GM brands.

Dosen't (numbers) show up on any other GM make.

It seems to be none of the above. This is a spiral bevel axle with hydraulic Huck brakes, the window is fairly narrow for when it could have been built.

Thank you Gene and terrill for the responses! I guess it is a real oddball.