Rear gear swap

[Speedracer39]

I have a 72 c10 with a 454 engine 400 trans and 373 gears 29 inch rear tires it is fun in town but not highway friendly. I am thinking about changing to 308 in the rear end and was wondering if anyone else has this set up. Or am I going to have to go to a overdrive to make me happy on the highway.

[demian5]

This has been beat to death. Use the search function in the upper right corner of the page.

[Speedracer39]

WOW —-must have been a rainy day in California

[TCCGRIZ]

Originally Posted by Speedracer39

WOW —-must have been a rainy day in California

Wow is right !!!
Personally I have no experience with your question but I know I have seen threads on it .
Easiest way to find them would be the Google search function on the board.
Hope this helps

[6768chevylover]

Overdrive is what I would do. Its so much nicer to spin the wheels with hammering the gas pedal instead of power braking to make them break loose.

[jessemthompson]

Originally Posted by demian5

This has been beat to death. Use the search function in the upper right corner of the page.

First off, this forum has a reputation for not showing it’s behind. If you have nothing constructive to add, don’t add!

To the OP, I would go with an overdrive. If you change to a 3.08, you’ll have to change your carrier out.

[cornerstone]

[quote= if you have nothing constructive to add, don’t add![/quote]

x2!!! THANK YOU!!! This is what our mommies told us and remember, mom is always right. I agree, get an OD transmission, like 6768chevylover said.

[Eddie H.]

Your cheapest option is going to a 3.08, even though you would need a different carrier. (good time to add a positrack carrier) , or you could probably find a complete rear axle with 3.08 gears pretty cheap. Going from 3.73 to 3.08 will make a noticeable difference in highway cruise rpm. Not as much as an overdrive, but much less expensive.
With a 454, you will have more than enough torque so that the higher gear ratio won't hurt city driving performance much either. In my 69 GMC, I have a small block 400, 400 transmission, and 3.08 gears, and it has no problems at all. I could melt the tires off of it if I ever wanted to.

[Keystone_Hate]

I have a 72 with a 350 and 4 on the floor. Used to have 373 and i went with 308 and a posi. It cruises at 2700ish RPM at about 70MPH. Not great, but its better than it was and way cheaper than a new trans. I'm happy with it.

[Speedracer39]

Thanks for all the feedback it’s always nice to hear what others have done and the likes and dislikes of both choices. I’m going to get together with a local trans shop and see how a 700r4 will work with my current engine as well as my block sitting in the garage that will turned into a 496 in the near future.

[1972RedNeck]

Originally Posted by Speedracer39

Thanks for all the feedback it’s always nice to hear what others have done and the likes and dislikes of both choices. I’m going to get together with a local trans shop and see how a 700r4 will work with my current engine as well as my block sitting in the garage that will turned into a 496 in the near future.

Don't do it. The best built 700R4 won't last behind a stock 454 let alone a mild 454 or especially a built 496. They just can't take the low end torque.

[chewychevy67]

I've been researching a gear vendor unit lately and that's what I'm using behind my th400. Looks like you would make better use of it than my setup will. You have perfect gearing/engine combo for it now.

[Speedracer39]

Originally Posted by 1972RedNeck

Don't do it. The best built 700R4 won't last behind a stock 454 let alone a mild 454 or especially a built 496. They just can't take the low end torque.

I have googled and found the same as you just stated. The machine shop that I use is the one who suggested 308 gears will have plenty of torque still to blister the tires. Gear venders overdrive was a thought but for the price tag I’m thinking gears will work out fine. Beings I’m shooting the wad on the motor Thanks again

[BCOWANWHEELS]

Drive it right and you,ll have no issues with built 700r4

[WorkinLonghorn]

Wasn't the 3.08 a car dif? I never heard of a truck with one. 67-72 had a 3.07 available but that's a different differential than a 3.08.
Anyway, I had a 3.07 with a 350 and 4 spd with 33 inch tires and I got 10MPG on the freeway at 60. Revs were very low. I know nothing about BBCs though. -BA

[BCOWANWHEELS]

tks have 3.07

[aerotest]

I have your combo with 3.08. Cruises at 2200 rpm at 60 mph. You would think it has overdrive. Works nice but not as much grunt off the line. It’s sufficient though. I am going to a 3.73 with gear vendors soon. Best of both worlds if you have the funds.

[Bigdav160]

Wasn't the 3.08 a car dif? I never heard of a truck with one.

Depends if you are rounding up or rounding down.

Technically 12 bolts (car and trucks) would be a 3.07:1 (14/43) and 10 bolts (cars or trucks) would be a 3.08:1 (13/40)

Reality is the terminology is used pretty interchangeably. This product is labelled as both 3.07 and 3.08

[volksworld]

if he wanted to "drive it right" why would he be building a 496?

[BCOWANWHEELS]

pulling torque