I have not been able to pull the cover off of my rearend yet, and check the gear size. So anyone who wants to have a go with it, be my guest.The rearend is an 8.2 GM 10 bolt. I have a 235x60x14 tire, on a 14 inch ralley wheel. I have a TH350, 3rd is still 1:1, 2800 stall. At 60 mph I am at 2550-2600 RPM. The rearend stamp says it's a 3.08. The fellow I bought the car off of had restored the entire car back to stock (EXTREMELY STOCK!), I'm not sure why he would go any different with the rearend, but I thought I was a little high in the RPM for a 3.08 gear.

Also, I wanted to ask you guys if you thought a 4.11 gear would be too much for my application, I want to beable to drive it an hour to the track, and I want to beable to highway it a little bit, The most highway it will see is that hour to the track though. It's pretty much a weekend warrior, wont have the time to drive it everyday once school starts again. This winter I am putting a 275x60x15 tire on my car, do you think with the change of tire it will be ok on the highway, or will it be not so bad on the highway now anyway? An Auburn Pro Series posi will be going in with it. Do you think I should stick to the 4.11, or go with the 3.73? I have a 283 with pretty stock internals, headers, intake, and carb. I dont have much time, so answers ASAP is greatly appreciated. Thanks!

Thanks again,
Joe Phillips

Probably is 3.08 gears. 2483 is the calculated rpm at 60. Allow for converter slip, the rpm you have is about right.

Originally posted by Jp-15:
An Auburn Pro Series posi will be going in with it.

Thanks again,
Joe Phillips FYI: If you get the Eaton posi it is rebuildable vs. the non-rebuildable (throw it away!) Auburn.

When I switched from 235-60-15 tires to 277-60-15 tires, my rpm dropped about 300 rpm at highway speeds.

I find with 4.10 gears, that in forth gear, I'm pretty close to two times the rpm, divided by 100 is pretty close to the mph.

That is 70 mph, is about 3500 rpm, in forth gear. (stick car).

I'd say 4.10s can be a little tiring, for long drives, but I don't mind too much.
(Not a daily driver)

Your little 283 might like the steep gear, and it will feel a lot quicker too, but 3.73 would most likely be easier to live with.

running 3.73 could be very tiring out on the highway even.......at 70 mph you would be looking at 3600 rpms to carry that speed with 255-60 -15 tires out back like my friends car which i drive sometimes......even for me thats to many rpms to carry over a long haul......

my car carry's 2.73 gears with a 2800 rated stall and 245/60 -15 tires and at 2500 rpms its nice to see im moving along at 75 mph.......

from the sound of it ..you want to drive it to the track and do some highway driving.....stick with a gear lower (number wise 3.23) then 3.55....... any more gear i think you will get tired of the rpms its going to turn if you are serious about driving it at 70 mph.............

even thou this seems extreme i ran my car for some time with 4.56 gears out back 4000 on up got real old in a hurry for driving out on the highway.......3.70 gears wasnt so bad (even had 275/60-15 tires) but if there was just a few more 100 rpms less it would have been better..........

i would shoot for a nice set of 3.55 gears between the 3.73 and 4.11 gears your not going gain really nothing runnin those over a set of 3.55 gears......performance wise......with 3.55 gears and 275/60 -15 tires your will be right around the 3000 rpms mark at 70.......

I run 3.73's witha 275-60/15 with a BBC. I usually drive the highway in the right lane at about 2800 - 3000 RPM. Still haven't bothered to calibrate the speedo, but that is about 63 -65MPH. Also, I run a 3000 converter and have found that it works well as a minimum to at least match your highway cruise RPM to your converter so the converter won't be slipping at extended highway driving.

take the advice of these guys, try 3.55 or numerically lower. my car had 2.56 gears from the previous owner, and i swapped in 3.73s with an EATON posi. i LOVE the performance, but driving to/from the track is somewhat of a pain. i have 2 drive in the right lane too, just 2 keep the rpms down. if u really wanna build the car toward highway cruising/mild rpm, i would stay away from anything more than about 3.55ish.

good luck! graemlins/beers.gif

Take the advise and go with 3.55. I have 3.73 on my 72 chevelle, and it does get boring after awhile, especially with loud exhaust!

I was running 4.10's in my 70 from April 2000-March 2004. I only changed them because the whine was so bad. The bozo I bought the rear from didn't set it up right. With those gears and a 28" tall tire, the car got 15 MPG on the highway as long as I kept my foot out of it smile.gif . This is with a 500 HP 454 resting under the hood. I drove it back from Eastern Massachussetts with the 4.10s rolling on the interstate at about 75-80 MPH cranking out 3700 RPMs, filled up once to get back to South Jersey.
I put 3.73's in it and there is not really a noticeable difference, only no more whine and maybe an extra .5 MPG.

I would put a 5-speed automatic with overdrive.
The overdrive would save alot of gas on the highway and the low 1st and 2nd gears would give you good acceleration. I am looking into this after I sell my TH400.

Originally posted by Chevelle007:
I would put a 5-speed automatic with overdrive.
The overdrive would save alot of gas on the highway and the low 1st and 2nd gears would give you good acceleration. I am looking into this after I sell my TH400. Haha You'll buy it for me? :D Just Joshin. I wish I could do that, but I just put in the TH350 that I had built. You guys say that you really didnt see that much of a difference from the 3.73 to a 4.11, should I just put the 4.11 in since I already have it? Or should I return it for the 3.73? A friend of mine has the same trans as I do with 3.73 gears, and we have the same exhaust set up, I dont mind the noise it makes on the highway at about 3000 he's doin 65 and he has smaller tires then I will have. So the choice is between 3.73 and 4.11.

Thanks guys!
Joe Phillips

JP-15, I'd advise that you keep the gears that you have in the car right now as more gear with stock cams only kill the gas mileage and does very little for performance. I'd also pass on the cone type posi-trac as that also will hurt the gas mileage. Just recognize the little 283 motors limitations and embrace its strengths,(economy), and save your money for the day you can swap in a more powerful motor. By the way, what kind of car is it in?

Hi Harold, Thanks for the advice. I plan on changing the cam in the motor soon to pick up a little more performance. In a couple years I plan on changing the motor over to a 383. I would like to beable to put just one gear in there and not have to change it when I change the motor, or even when I change the cam in the 283. I'm not worried about gas mileage too much right now as I won't be driving the car all the time. I'm trying to get bumped down into 14.9's with this motor. I think the 4.11 gear with a cam and some stickies could do it for me. The motor is in a 1966 Malibu.

Thanks for the help,
Joe Phillips

Hi Joe, This is a good car for a bigger small block on down the line. Your thinking about a 383 cu. in. one is right on the mark as this year Chevelle is fairly light, (about 3200 lbs.), with the little motor. Good luck and don't hit the 283 too hard so everything will be usuable when the bigger motor comes along.