Rear axle ratio

WZ JUNK · January 08, 2016, 01:10:10 PM

The Lincoln rear axle in the 1954 Chevy is a 2.75 to 1 ratio. It probably came from a car that was not AOD. My information on the Chevy Caprice donor car, that I used the TBI engine and 200R transmission, says that it probably had a 3.08 to 1 ratio rear axle. The 54 will use a little bigger diameter rear tires than the Caprice. So the end result will be a higher ratio than the original Caprice donor. The Caprice was design for the slower speeds at the end of the gas saving 55 MPH era. I wonder what this difference from 2.75 to 3.08 will mean. This is to be a highway car and not built for performance, but just a good travel car with enough zip to climb a steep hill comfortably, or pass another vehicle easily. When I get into terrain that is hilly and curvy, I could shift out of OD to D. Will spending the money to change the ratio justify itself ?

What do you think?

John

enjenjo · January 08, 2016, 03:46:16 PM

I think you will be fine. I built a 48 Ford with the same combination, and it drove fine. The overdrive was pretty much highway only though. The 200R4 has a pretty low first gear, so they are not a dog from a stop. And if you want to change it, 9" gears are still pretty common.

chimp koose · January 09, 2016, 12:00:32 AM

I would leave the gears alone ,your 54 chev is likely a fair bit lighter than the caprice the driveline came out of . Drive it as is and if the performance bothers you , then look into a change .

parklane · January 10, 2016, 04:00:54 PM

A friend has a 305/700R4 in his 54 Chev with a lower gear than yours, and it works really well.

58 Yeoman · January 10, 2016, 06:14:11 PM

I'd bought a rear axle out of a 64 Merc that was supposed to be a 3.00 according to the tag. I've been told that that was a good ratio for the Caddy 425 engine in the 41 Poncho. IIRC, it turned out to be around 3.55. You can't always believe those tags.

kb426 · January 10, 2016, 07:28:06 PM

John, depending on all the factors for calculations, I decide where the engine will be good at 65 mph in od. Most of us have a tire size in mind for stance so the gear ratio is the variable. You have enough info to make the decision.

WZ JUNK · January 11, 2016, 07:51:00 AM

Thanks to all those who responded. I believe I will leave the existing ratio in the car until I can drive it some. Changing the ratio later will not be a big problem.

John

papastoyss · January 13, 2016, 12:54:49 PM

Quote from: "58 Yeoman"I'd bought a rear axle out of a 64 Merc that was supposed to be a 3.00 according to the tag. I've been told that that was a good ratio for the Caddy 425 engine in the 41 Poncho. IIRC, it turned out to be around 3.55. You can't always believe those tags.

That 3:55 is a good choice if you're using a 700R4/4L60 trans.

58 Yeoman · January 13, 2016, 01:54:11 PM

Quote from: "papastoyss"
Quote from: "58 Yeoman"I'd bought a rear axle out of a 64 Merc that was supposed to be a 3.00 according to the tag. I've been told that that was a good ratio for the Caddy 425 engine in the 41 Poncho. IIRC, it turned out to be around 3.55. You can't always believe those tags.
That 3:55 is a good choice if you're using a 700R4/4L60 trans.

No, it's got the TH400.

papastoyss · January 19, 2016, 12:23:17 PM

W/the T400 & that big motor I would look for something in the 2:80 -3:00 range for highway use.

58 Yeoman · January 19, 2016, 04:08:48 PM

Quote from: "papastoyss"W/the T400 & that big motor I would look for something in the 2:80 -3:00 range for highway use.

Yeah, that's what someone else had told me, and that's why I picked that particular rear end. But someone must've changed the tag. No big deal for now. I may not be getting that car on the road after all.