Originally Posted by Grigg
Someone mentioned 0.63 OD ratio as a good idea.
I don't think it is a good idea for a truck with limited HP.
Grigg

I made the comment that the 0.63 OD would be a good match with a 4.10 rear diff. I cannot be dogmatic about my opinion because I have never driven with a 0.63 OD gear and a 4.10 diff. I just looked at the math.

As I understand gearing, the engine doesn't "see" individual gears. It just "sees" the final math of the combination. The overdrive gear of 0.63 X the 4.10 diff = 2.58. Another way of achieving the same final drive would be to have a 2.58 diff with a 1:1 4th gear. The engine doesn't know the difference between the two examples.

My truck is a 1/2 ton, so it's lighter than a 1 ton, but I do have personal experience with it. My 0.73 OD gear X the 3.73 rear diff = 2.68 and I love the power I have in 5th gear. I can let the RPMs drift down to 1600 and climb right back to 2100 without bogging the engine.

So I do think a 2.58 final drive would perform much like my 2.68 final drive. I will say that the 0.63 gear is a HUGE drop from the 1:1 ratio 4th gear. If the truck would see a lot of hills, then it would be nice to have a gear between the 1:1 and the 0.63.


The 0.73 OD gear would also be very nice and are found in some S10 models and most V6 Camaro T5s. The only catch is that those same S10 and V6 Camaro T5s have a 3.75 1st gear. That would put the 1st gear math at 15.375 which would make 1st gear very low. The world class V8 Camaro T5 has a 2.95 1st gear and brings the 1st gear math number down to 12.095 which seems OK for a 1 ton first gear. HOWEVER, the V8 Camaro WC T5 is always 0.63 overdrive - and that is the very reason I suggested the 0.63 OD gear with a 4.10 diff.

The V8 Camaro NWC T5 has a 0.73 OD gear but is very hard to find.

1965 Chevy C10 Shortbed 1/2-Ton Stepside
Truck College
In the Stovebolt Gallery
In the Project Journals Forum
The Build BLOG on Weebly
T5 Transmission Build page