The Stovebolt Site Forums The Shop Area Driveline Is the high speed rear end upgrade worth it?

I'm at the point of doing the rear end upgrade on my 41 with 235 with 3-speed. Everything is standard except the 235. Will I be unhappy without the upgrade, what are the thoughts? Dave

depends entirely on how much you'll be driving it and where, your grandad put up with slow speeds

Bill

OK, can anyone tell me what would be the comfortable top speed for this truck in the original condition?

45mph down hill with wind pushing you.

Assuming that you have the original rear end with 4.11 gears, and assuming you are running a bigger optional tire like 6.50x16 (29" tall) you would be topping out at 63MPH which is 3000RPM. That is also assuming that your 235 is '55-'62 vintage. If the motor has been re-built and balanced this is your max. speed. I wouldn't run any 235 over 3000RPM max. If you have an early 235 from '41, it has babbitt bearings, in that case I would not push it over 50 MPH 2380 RPM.

"comfortable" top speed would be about 45-50 if your brakes are top notch and the road is decent, regardless of the engine - the brakes and suspension are the real limiting factor, these vehicles weren't built for comfort nor designed with modern roads in mind, at a sustained 50mph the driver is the first thing to give out

Bill

I agree with red58, I neglected to mention brakes, steering components, suspension, and road conditions are all important factors in determining top speed. Safety First!

Thanks, everything is being addressed, new kingpins, tie rod ends,bendix brakes on the front, new shackles and pins and spring end bolts. I'm doing everything, I guess with all that said I don't really need to go much over 50. NO interstates around here. Yes it is a full pressure 235 just rebuilt, trans rebuilt, I guess I should go through the rearend and check bearings and all that. Thanks for all the comments. Dave

With a 3spd, 7.50x16 tire and 4.11 rear (and a 216) I can keep up with the slower traffic on the highway pretty easily. Steering and stopping are what concern me more. I'd do the gear swap if you plan on running it at freeway speeds for extended periods of time.

I did a 400 mile round trip last weekend and in my area 70-75 mph is about average for the right lane and 80-85 in the left. With the 3:55 gearset and a warmed up 235 I can keep up and use the left lane occasionally. Bumps can get a little intense at those speeds with the solid axle though.

My 39 with a 216 had 4.11 gears. Got tired of hearing the engine putting out high rpms at 40-45 mph floored. Had 3.30ish gears made for it. BIG difference. I can cruise at 55 mph with plenty of gas pedal left. It has great steering, brakes, and suspension. I do need to replace the tires next Spring. Undecided to use bias or radial tires.

rickmg - How's torque and acceleration?

The transmission in my 39 is an original 3 speed. With the 3.33 gears rather than the 4.11 there is a torque/power difference in 1st gear taking off from a stand still. Not enough to make it a nuisance. I can still idle down the road in 3rd gear, give it gas and accelerate. I've owned and driven this truck since 1977. I changed the gears 6 years ago. I wish I had done it sooner. It is much more enjoyable to drive. The bonus is I get 20+ miles per gallon.

Mothertrucker has the gears in stock. [email protected]

Dave,

I think you'll be happy with the upgrade. I rebuilt my rear in my '53 several years back and could notice a difference quite easily. I still have the original 216 in mine and can only imagine a full pressure 235 would be better equipped to handle highway speeds.

I've driven both before and after the upgrade down I-5 through Seattle and it was not very enjoyable of a trip with the 4.11 gearing. I could actually pass people with the 3.55 gearing!

I think you can expect to pay around $700 for the gear set and bearings if my memory serves me. It's worth the price in my opinion.

Jeff

My 49 is stock except for a 235. 3 speed, 4:11 rear end and 650-16 bias-ply tires. Have owned it 14 years driven around town at 40 mph and once in a while it goes on the highway. I sit fat, dumb and happy at 55 mph. I am of the theory if it was designed by a bunch of GM engineers to operate as it does then why would I need to modify it. My opinion.

1956 235s were used in cars and trucks with tires/brakes/etc that were not very much more advanced than 47-55 equipment.

The pre-54 engines, being low-pressure and having babbitted rods, might have been matched with the 4.11 due to the older technology, slower speeds, and/or maybe the older roads.

The high-pressure 235 came out in 1954 (in trucks) and so did a 3.90 rear end. 3.70 rear ends were stock in many 1956 cars (with 1956 235 engines). I think the available overdrive had an affective rear-end ratio of about 3.28. So, apparently, the GM engineering of the rest of the vehicle might have been designed to handle that rear-end ratio and resultant higher speeds?

Nonetheless, I am also hold the opinion that I prefer my vehicles the way that "god" (their maker, GM) made them. However, I can live happier and quieter with the hidden 3.55 ring & pinion gears (and, I am really glad I used the installation kit parts).