4.11 gears

[51chuck]

I have a 1951 Chevy 3600 truck.
It has a 4.57 gear ratio and I am looking for 4.11 gears, or are there other gears that might work to increase the truck speed?
Where might I find some?

 

[Bill Hanlon]

I have a 1951 Chevy 3600 truck.
It has a 4.57 gear ratio and I am looking for 4.11 gears, or are there other gears that might work to increase the truck speed?
Where might I find some?

First, realize that changing from 4.57 to 4.11 will net you only 11% increase in speed at the same engine RPM. If you top out at 50 now, you'd make it to 55 assuming your engine had the power to pull the additional load.

You probably already know this, but the whole center section is interchangable between 3600/3800 Chevy and 150/250 GMC starting in 1946 and going into at least the early '70s. Some of the later model 3/4 ton, larger V8, automatic transmission equipped vans had this same center section with 3.73:1 gears. Those gears would give you a 22% boost in speed at a given RPM.

Sadly, I don't know where to find either.

My 3/4 ton has a complete rear axle from a late 60s GM car with a 3.55 gear. The stock six cylinder engine is happy going down the road at 65 MPH until it gets to a hill.

 

[51chuck]

First, realize that changing from 4.57 to 4.11 will net you only 11% increase in speed at the same engine RPM. If you top out at 50 now, you'd make it to 55 assuming your engine had the power to pull the additional load.

You probably already know this, but the whole center section is interchangable between 3600/3800 Chevy and 150/250 GMC starting in 1946 and going into at least the early '70s. Some of the later model 3/4 ton, larger V8, automatic transmission equipped vans had this same center section with 3.73:1 gears. Those gears would give you a 22% boost in speed at a given RPM.

Sadly, I don't know where to find either.

My 3/4 ton has a complete rear axle from a late 60s GM car with a 3.55 gear. The stock six cylinder engine is happy going down the road at 65 MPH until it gets to a hill.

Thanks Bill
My brother and I will look into this info and let you know if we have any luck.

 

[Chiro]

What Bill said. I know of a few people that have done that swap and are very happy with it. You might want to upgrade the brakes after now that you can go faster.
Andy

 

[coilover]

I don't waste my time looking for hens teeth so just go to Rock Auto and order a ring and pinion (R&P). There is 3.42 available for the 8.875 R&P which most have or 3.55 for a Dana 60. If the truck is just a cruiser the shallow gears are fine but if a load hauler or trailer toter then the 3.73 would be better. 8.875 R&P $160, Dana $202. One used to have to change carriers at the 3.73 break but now they offer thicker ring gears to compensate.

 

[Bill Hanlon]

Stock is a H-050 from GM, Evan. He'd have to change the whole rear axle.

 

[51chuck]

After some research it looks like a 67-72 chevy 3/4 ton C20 diff will interchange with my 51 diff. So I should be able to order a 3.73 ring and pinion for a 68 C20 and it should be an easy swap out. Am I right or wrong?

 

[Bill Hanlon]

I don't know if the ring and pinion will interchange. I've heard that the whole "chunk" will interchange. I've never done it personally.

1950 through 1960 use the same part numbers for the differential carrier and all associated parts. I don't have documentation any newer.