Rear end gear ratios

[markabailey]

Hello all,

I am in the process of changing the original stock factory 3 speed on the column manual transmission to an PowerGlide 2 speed automatic transmission on my 65 model 1/2 ton Chevrolet pickup. I have purchased an 64 model chevrolet pickup from a gentleman to be a donor truck for my project here. It has the original stock factory 2 speed PowerGlide transmission in it. It is all intact as well to include the transmission, steering column, crossmember, radiator with internal ATF cooling tank and driveshaft. It was a real jewel to find for myself having all of these original factory parts in it. The truck itself is not worth tring to restore, but the transmission components are still good in it. I am having the transmission rebuilt currently.

My question is will I need to change out the rear end in my truck when I put this 2 speed PowerGlide transmission in? I do not know what gear ratio either truck has in it currently. By keeping in my existing rear end and installing the PowerGlide transmission and components, will this be acceptable for my truck? I want to be able to drive the truck at crusing speeds on the highway at 55-65 MPH and hopefully at the same time be able to not do any damage to the engine due to excessive high RPM's. I might do some hauling with the truck in the future, so I want to be able to pull a load with it as well. I realise that gas milage will not be good with this transmission any way you go, but I would like to have the "best" possible gas mileage as well.

Could anyone help me with determining the gear ratio of the rear end in my truck currently through identifications on the rear end, VIN number, ect? Also, what would be the BEST rear end gear ratio for the truck to have once the 2 speed PowerGlide transmission is installed? Like I mentioned above, the truck that will be recieving the PowerGlide transmission is a 1965 Chevrolet 1/2 ton LWB fleetside with a factory stock original 3 speed on the column manual transmission.

If anyone could help me in this it would be much appriciated. Thanks again and I look forward to viewing your posts in the near future.

 

[JQ_72]

I might can help a little. I am a '65 owner also and have done
a lot of research on 64-66 data,options,etc. One inportant factor
is what size engine your truck has. Most all 6 cyl. engines
came with a .373 gear ratio regardless of trans. type. I'm not
positive about this, but I believe most 8 cyl. trucks had the
.307 ratio. I recently put a powerglide in a '66 truck that was
originally a 3-speed. It was a 6 cyl. truck and had the .373
rear end. I couldn't tell any difference in the engine rpm's.
If you have a v-8, the .307 ratio is the way to go (good hwy.
speed and pulling power).

 

[Richard]

Hey, Mark

Might have a little info for u goto americanclassics.com
and at the bottom click on vin info andit will give u
rearend ratios for both trucks.


any problems

e-mail me at
Badbowty37510889@Gateway,net

 

[ftyler]

It seems to me that the 3.08 is a little too high to run with the powerglide, considering that the powerglide has an extremely high "low" gear ratio (1.82).

Seems that take-offs would be s-l-u-g-g-i-s-h, and the extra effort to get a heavy pickup moving with such tall gears would put strain on the transmission's clutches. Somebody correct me if I'm wrong.

With a powerglide, I'd stay with a 3.55 or lower (numerically higher) gear. I'm not sure if GM mated any high speed rear ends to the powerglide. It's worth checking into.

-ftyler