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

Yes, I would love to see a photo. I did see the photos, before they disappeared, and I thought I saved them, but I am not finding them now.

This isn't the road I am currently going down, as I have a 3.82 ring and pinion.

I researched and read about this every way I could, including your method, or an aftermarket 3.55 ring and pinion (you know why this one wont work), Mitchell overdrives, Borg Warner overdrives in the torque tube (as seen in model A and Buick circles), Laycock aka Gear vendors overdrives, The possibility of a Jeep or Studebaker top shifter plate on a rambler t86 with overdrive, Warner T5s, and a few other things... I could go on about this subject for hours.

I wanted to not change it too much, but the 4.88 is ridiculous. If I successfully get this 3.82 built I can just change the center section with the torque tube and be done. Most people don't have the option of doing this, as the 3.82 is rare as hens teeth. I do wish it was higher. Also the 36 axle is expensive to rebuild, and likely to be all screwed up when you look inside. I suspect you know all this....

I was looking for a 1937 housing to modify like yours until i got the 3.82. It is possibly a little more involved than what you did because the Pontiac has Bendix brakes instead of Huck. They made a change in mid 36 in the way the backing plates attach to the axle housing I'm guessing one of the two types would just fit the 37 Chevrolet housing, but Im not sure. Regardless, none of this is insurmountable anyway as I have access to a lathe and a mill here.

What is the the center to center distance between your 36 truck rear leafs? I know you had to move them in on the 37 housing.

"This isn't the road I am currently going down, as I have a 3.82 ring and pinion."

Bloo,

It is my understanding that the 3.82 factory "economy" gearset is not a bolt in because the 3.82 ring gear requires a unique differential case that is also extraordinarily rare. In the 52 years I've owned my '36 I've never seen a 3.82 gear set nor the required differential case offered for sale. Also, there is the question of how much of a gear change you want. Will a 3.82 get you there?

"I researched and read about this every way I could, including your method, or an aftermarket 3.55 ring and pinion (you know why this one wont work), Mitchell overdrives, Borg Warner overdrives in the torque tube (as seen in model A and Buick circles), Laycock aka Gear vendors overdrives, The possibility of a Jeep or Studebaker top shifter plate on a rambler t86 with overdrive, Warner T5s, and a few other things... I could go on about this subject for hours."

Yes, there are certainly many ways to approach this task. Here's another; years ago I met a guy who had grafted a Volvo OD into the torque tube of his Model A Ford. He said that the stock engine pulled the A at freeway speeds with no bogging problems. It gave him the option of 6 forward speeds but was an obvious modification,

I'm away from home for a few days but I'll be glad to send to the measurements between '36 spring perches. I saved the original rear axle so it's no sweat to get that dimension. If you don't hear from me within about 5 days please remind me. There is the risk of a possible "senior moment" that I usually deal with by doing stuff "right now" but that's not an option until next Wednesday.

I will look to see if the photos are saved anyplace except in the article. If not will the whole article, with photos, work for you?

I'm really glad you found the information in my article interesting.

Ray W

I used to think so, but after poring over the parts book until my eyes crossed, I now think that it is the 3.82 gears for the Chevrolet Standard that require a special differential case. As I'm sure you know, the Standard is a whole different rear axle.

I now believe the 3.82 gears for the Master and 1/2 ton use the same differential case as the 4.11 (and probably all the others). So, when the gears were offered, I jumped. I really should mock it up and see as I have the 3.82 gears in my possession.

Interestingly, the only piece I am currently missing is the differential case. Both of the ones I have are damaged.


I dont know.

I wanted more. It is fairly easy to calculate how to get to what rpm at 60 you might like, but then will the engine pull it? My best guess was 3.55, for a whole bunch of reasons, including things you have posted elsewhere, as well as the fact that all the aftermarket gears for the Chevy sixes with hypoid axles are 3.55. Larry Jackson made some sets of about 3.32 or so for the 36 rearend. Not very many. He isn't making any more. I would be willing to try it, but you cant get it. I hear those worked out well, but it does sound a bit high. My tires are 600-16.

The short answer is 3.82 is the highest thing that I could get for this axle.

The Pontiac engine is a 208ci flathead with precision insert bearings and full pressure oiling. In theory it should survive being wound up longer than the 207ci Chevrolet. Maybe 3.82 will be enough. It is so difficult to judge how much torque the engine has because the gears are so low. On the highway it will gain speed on any hill in high gear, no matter how steep. I have only had it to 53mph though. It would go faster, but it is just screaming at 53.


Yes, thank you! From the article (how far the springs mounts were moved) I should also be able to extrapolate what that distance was on the 37. I am not in a hurry for this information as I doubt I will be able to tackle this project again until early winter.

1935 Standard 3.82 ring gear and pinion part #601749. requires use of 601755 case.

1936 Standard 3.82 ring gear and pinion #602044 requires caes # 602031.

Late 1935 and all 1936 Master and late 1935 and all 1936 1/2 ton trucks ring ggear and pinion (3.82) 602477 existing case is used. Special case not required.

The case (part ring gear attaches to) is different for the Standard models due to the pinion gear being larger in diameter and would contact the housing. The case from a 4.11 would work but material would need to be removed in the area the ring gear attachw=es to to bring the ring gear away from the carrier.

The Master hosing has enough room on the sides so the case change is not necessary.

The same is true when a 3.55 is installed n a 1940-1954 rear end that had a 4.11 ratio.

The 3.82 will reduce the 3000 RPM at 60 MPH to about 2800 RPM.

The 1936 Pontiac uses case #602276 for a 4.11 and I do not see ths number for Chevrolet. Actually the Pontiac case is different for each of the three ratios Pontiac used.

My two cents:
Any gears lower than 3:55 (higher numbers) is not enough return for the effort. As Gene and others mentioned, 3:73 is still gonna rev pretty high RPMs.
Also consider the rear tire height can be changed with different tire manufacturers will help to deal with the gears you already have. Any way you decide to go will be an improvement. Most important is lowering the RPMs for preservation of our precious engines. The reward when we accomplish what people say can't be done is pretty cool too.

I should have mentioned that ring gear and pinion # 602477 was also used for 1937-1939 1/2 ton trucks when a 3.82 ratio is desired.

I would say a ratio like 3.73 is ideal for replacing a 4.11. It reduces engine speed by 10 percent which doesn't sound like much but makes for a dramatic change for highway driving.
With a 216 engine it makes 65 MPH a confortable driving speed with the engine turning less than 3000 RPM.
If it was available for a 207 engine 60 would be a comfortable speed with less than 2800 RPM.
At any of the above speeds you will still look like a turtle when driving on a freeway or interstate.

To add another reference point I am very pleased with the overall performance of my '37 Master coupe with a 3.73 axle.

Most of my driving is around town with a lot of stop and go. It accelerates well enough to keep up with traffic. I do drive some portions of the interstate within the area and 65 is not a problem although it gets pretty noisy. It really runs well and is enjoyable to drive at 55 to 60 on the 2 lane roads.

My 207 engine in 3rd in overdrive gives me around 3:25 gears (4:11 rear) on the highway. I just think 3:73 would be minimal.

Thanks for the responses everyone!


I did not know that. Could those numbers be with the ring already riveted on? The "parts book" Early Times Chapter (Pontiac) has posted shows 364538 (like a Chevy) for all 1935-36. I don't think it is an original book, so it could be wrong, I guess the implication is that the differential case will have to come from a Chevrolet. That isn't a huge stumbling block as both of my Pontiac ones are bad.

http://chevy.oldcarmanualproject.com/parts/1929_54/351.htm

https://web.archive.org/web/20170317194133/http://www.earlytimeschapter.org/documents/1935-36_parts_book.pdf

You know I have 4.88 right now, right? It will definitely be a noticeable change. Yes, it still sounds too low. I love this car, but it's too slow to take out of town.

I may need to make an axle like Ray's after all. I had a 53 belair with a stick and a babbit-pounder 235 when I was a kid. The 3.70 gears seemed about perfect, but then I remember the speed limit was 55 then.


That 4.11 and borg warner overdrive setup was common in a whole bunch of cars. I had a Nash with that. It really does make a tiny engine usable. Knowing what you know now, having driven your overdrive, would you have picked 4.11 to use with it if it wasn't already there? If not, would you go lower or higher?

I know you have the 4:88. I am sure your tranny gearing and tire size play into the equation. You can't push the brakes, front end, steering, etc. It is dangerous. Cruising at 55-60 mph at 2200 rpm's is a million times better than 55-60 mph at 4000. It makes you feel like you are going faster knowing you have more pedal and the anticipation of seeing your pistons all over the highway is gone! I don't know your car but we can all sympathize. Try to calculate what you need to reduce your rpm's to 2200-2500 at 60 mph. Factoring your hilly terrain you don't want to overwork the engine so 3:73 might work for you. Ray's set up would have been my second choice.
I have tripled the miles this year venturing further away with the OD. I looked at all my options and the convenience of already owning the OD and Mike's spare rear and torque tube made my decision for me.
As far as the 4:11 with it I know now that if I had a lower gear (3:55 - 3:73) with it the engine would have bogged at lower speeds. I only use the OD in third. It is not mountainous here on Long Island. For my situation it is perfect.

I missed that this morning. Was doing the research before breakfast.
Each Pontiac ring gear and pinion came with the correct case attached.
The Pontiac 4.11 gear and case is the only one from the bunch with a number series that Chevrolet used. I would be willing to bet the 4.11 came with the Chevrolet case and it has a similuar part number for the case of 602476 by coincandence.
For a simple change the 4.11 with the 6.50X16 tires would make the smooth straight eight very smooth up to at least 60 MPH.

My car guy uncle always called the Pontiac eight the "lazy eight" because of the lack of power for an 8 cylinder car. It was quite a small 8 with only 232 cubes.

Just checked my 1935 parts book The 601276 ring gear and pinion and case is listed for late 1935 Master. Does not appear in 1939 parts book.

HA! Well, this is a lazy six I guess. I have often wondered what they were thinking, as in a given year the Pontiac six and eight were always very close to the same size. The engine design is even very much the same. The cars are the same from the firewall back. They just added length to the nose to make room for the eight.

My tires are 600-16. That is 28 inches tall, at least in theory. I have good bias plies on the car, and a set of radials already here, also 28 inches tall. looking for wheels....

I did consider getting taller tires like 6.50 or 7.00, but I like the way it looks with the little 6.00s, and also radial choices are very limited in 16 inch.

The only older Pontiac 6 I ever drove was when I started in the dealership in 1950 It was a 6 Standard and was the slowest car on the used car lot. Looked like a low mileage original car at that tme.
Like I said, it was the only one I ever drove.
I had a 1935 Olds 6 and it had the strongest high gear of any car I had but had a 4.40 rear end and an over sped engine.

I know it is a different situation, but I once did the 3.55 (Power glide) gear conversion to an, otherwise stock, 1951 1/2 ton pickup. I moved the spring mounts on a '48 passenger rear end and modified the driveshaft length.
I did not convert the rear bakes because the truck owner decided not to do it.
The overall drivability of the truck changed dramatically. I would do it again without thinking twice.
My buddy, the owner of the truck, was not planning to haul hogs to market or lumber to a job site so a slight reduction in hill climbing performance was not an issue.
I was planning to use a PG gear set to build a rear axle for my '35 Standard but my situation has changed and I will not be making that modification. I have a '54 PG rear axle in reserve in case another need arises.

Mike

Bloo,

The center to center distance between spring perches on my '36 PU is 40 1/2 inches.

I'm slow in getting back to you on this because I'm in Santa Rosa CA where the fires you've been seeing in the news are. We were finally allowed to leave the evacuation center yesterday, a college campus, and come home to a house still standing. Others are not so lucky. Whole neighborhoods have been reduced to ashes as literally thousands of residences burned. The sky is still filled with smoke from fires still burning over a week after this all started.

Ray W

Sure glad your home is okay. It is a tragedy still happening. Don't know about several VCCA members in the Santa Rosa area. Sure hope their homes are okay too.

Some folks have used a S-10 rear end. Seems that the '36 rear hydraulic brakes are close enough to the S-10 fluid requirement that no modifications are necessary. Emergency brake is a different story but understand it is not too difficult to hook up.

Thoughts and prayers go out to all affected

Wow!

Glad your home is ok. Hope you and your family are all fine. Thank you for posting the measurement.

bloo, let me know if you need any photos of the project. I think they are all on this forum at this link:

https://vccachat.org/ubbthreads.php/topics/334876/1936_Chevy_3.55_rear_gear_conv

Ray W

Bloo,

I sold you that 3.82 gear set back in December. I agree with you that they should fit with the differential case in your Pontiac. In 1936, Pontiac offered three separate rear end ratios: Standard was 4.55 for the 8 cylinder and 4.44 for the 6 cylinder; Plains ratio was 4.11 ( 6 and 8 models); and Mountain ratio was 4.89 (both models. I had a 36 Pontiac Deluxe 8 Business Coupe, and it had a set of 4.11 gears in it that were from a 37-39 Chevrolet 1/2 ton truck.

I found the 4.11 gear ratio to be quite satisfactory, giving a good balance of torque and speed. With 6.50-16 tires, at 65 mph, the engine was turning at 3,250 RPM, which seemed to be reasonable for the 8 cylinder motor. In fact, with the engine rebuilt, I drove it at 3,500 rpm (70 mph), and I believe it could sustain that speed all day with no problem. With the 3.82, you could expect the engine to be turning about 3,000 rpm at 65 mph, but you'd also realize a 7% loss in rear wheel torque, which would manifest itself in requiring more throttle to hold the higher speed. Based on my experience with a 3.55 ratio in my 37 and 40 Chev pickups, I would prefer the 3.82 over the 3.55 for extended highway travel due to the limited hp/torque of the Pontiac motors.

I'd be interested in knowing if and when you get the 3.82 gear set installed in your Pontiac, and how you like it.

Incidentally, I embarked on a road trip from Reno to Maine back in June in my Pontiac, but I hit a deer in Wyoming, which mangled the left front fender and tore off the left headlight. Luckily, the car was still drivable and I drove the 865 miles back home without incident. Disheartened and not wanting to deal with the repairs, I sold the car, as is, in August.

Mark

Mark, sorry to hear about your car.

I hope to get the 3.82 put together this winter. Since I bought the gears from you I have parted out 2 36 Pontiac axles, bought all the bushings and bearings (all but one are not readily available), and had the best driveshaft out of the pile spray-welded and re-machined. I even found a riveter in Seattle willing to take on riveting the ring gear.

One of my parts axles had 4.11, and whoever riveted the ring gear on that one managed to bend the case. I could have it machined straight, but it would still be at the limit for in/out runout (eccentricity). It had also spun one bearing in the carrier, but just barely and had not done any real damage.

The other was a 4.44 that had rust damage and had spun both bearings on the differential case. The bearing mounting surfaces on that one are fairly shot. I suppose It could be spray-welded, or the bearings loctited on, but I am hoping for a better case.

I am picking up another axle soon. Hopefully the case will be good. The case really is the only holdup.

I would be ecstatic if this car would do 70mph indefinitely, but I was not really expecting it. I have the 4.89 now and am not comfortable taking it over 53mph. 45 is more like it for extended periods. I was hoping for a steady 60mph. My tires are 600-16, and the new radials I bought are dimensionally the same.

I am also looking for more wheels. I bought a set, but they are basically junk. If you know anyone wanting to sell some, send them my way.

Extrapolating from this chart: http://home.znet.com/c1937/RPM.htm 3500rpm with 3.82 ought to be about 75mph!

How did the torque of that Pontiac 8 compare with your trucks? Did it have aluminum pistons when you were running it at 3500rpm? Are the trucks 216s?

Ray,

Those pics seem to have been lost in the photobucket cash grab. They are probably still in your account where you can see them but nobody else.

I just found the PDF, so I have them now.