The Stovebolt Site Forums The Shop Area Engine Shop 3:38 ratio in a 56 chevy 3100 pickup with a(4-speed) 235 engine.

Can anyone give me any info or has anyone tried a 3:38 ratio in a 55-59 chevy 3100 pickup with a 4-speed transmision and a 235 six cylinder, I'm having the rearend gone thru as I write this and would like to no if it is worth putting this in while it is apart, I drove the truck before restoration and found that she winds out pretty good at 50 miles an hour,any help on this would be greatly appreciated. THANKS STEVE M. :rolleyes:

Which engine? Size does matter!

I think 3.38 is a pretty good ratio for a 216 or mild 235. I am going to 3.08 with my 261. With a 3.08, your engine will be turning 2360 rpm at 60 mph, which is pretty good.

I've got a '59 shortwide with the 4wd conversion. I'm running a 261 and the SM-420 four speed. I put the 3.38 gears in mine (front and back of course). I'm pretty happy with it but it's a pricey conversion(doubly so in my case). With the limited rpm range of the six I don't think you can expect more than about an additional ten mph from the conversion. Before I put the 4wd stuff in I had a three speed with overdrive and the conventional 3.90 axle ratio. The overdrive was much better than the 3.38. Unfortunatly it would have been too much engineering(for me anyway) to keep the overdrive with the transfer case. Another thought is the 5 speed T5 tranny. I think that would be ideal with the 3.90 ratio.

3.38 with a 235 can be marginal. With the right diameter tires that put your road rpm in the 2,400 range you should be okay if you're not in the mountains. There are several on-line rpm calculators, I usually go to Randy\'s Ring & Pinion

Eric:
I'm doing a NAPCO conversion on my 1957 Chevy - long bed. I want to keep the 3-speed OD trans (I have three of them actually). I have a divorced transfer case. What was the problem the caused you to drop the 3-speed. Thanks.

I don't remember for sure(I put the Napco stuff in 10 years ago) and I don't have my truck here right now to look at. I think it was something to do with the tranny outputs. The 3 speed has a splined shaft output to accept a slip joint on the driveshaft and the four speed output has a U-joint yoke? Something like that. Maybe I just assumed it wouldn't go and didn't look at it hard enough. I'm sure it can be done. With your long wheelbase you will have more room for any adapter you may have to make for the shaft between the tranny and transfer case. My truck is a short one and there is not much room between the tranny and the transfer case. Rear driveshaft angle is pretty severe also so I wouldn't want to move the case back any further.

I have also considered this, but have been told that a 235 I6 will/may not pull off the line with a 3.38 ratio. I sure wouldn't go any higher than that. For this reason I am looking for a 3 speed with OD for my 59 with a 235 I6.

Eric, any chance you still have the 3 speed OD kicking around and would like to sell it?

I have 1956 Chevy 3100. I have owned since 70’s. I installed 3.38 gears about two years ago after my 3.90 ring and pinion wore out. It was the best money I ever spent on the truck. At 65 mph, it improved mileage about 3 to 4 miles per gallon, plus the cab is so much quieter and the engine seems so much happier to cruise at lower RPMs. The 235 has plenty of torque to launch the truck just fine even with a bed full of firewood or to pull my boat.

NorthernGMC; Yes I still have the 3 speed + overdrive but I'm hanging on to it in case I want to use it in another future truck project. They aren't getting any easier to find.

The 3.38 gears pull off the line just fine. Even with tall tires and pulling a trailer. Low end torque is what these stovebolts are all about. You're not going to smoke the tires but if you want to drag race you don't want a 235 anyway.

Since you have a 4 speed anyway you will be able to get just about anything moving in 1st gear anyway, I would go for it.

We have a 46 3/4t. We have found a ring and pinion with a 3:55 ratio for 47 - 54. Does anyone have any advice as to wether there is something like this out there for our truck.

Tempest

We are both more body people then the mechanical side of things.

I'm at the start of the same project with a '57-1/2T but with a 350 and a 4.10 rear. I want a highway gear for mileage as I started saving the tires long ago.

Am I correct that the group likes the 3:36 for this. Other options??

Thanks in Advance