What rear end do I have?

[Sams '66]

70 mph at 2900 rpms.........anyone?

thanks

Sam

 

[youwish2bme]

Wouldn't that be a 3:36???? I thought though that all L79 came with 3:70's... What does the case say? AO I think is 3:70's. I'm sure someone will chime in with the correct info because I'm just taking a guess.. You could always jack up the car and turn the wheel one revolution and see how many times the driveshaft turns..Dave....

 

[61 Silver]

Hi!
There is a post on the NCRS web site on the same topic. If your components are the same, the answer is a 3:70 differential. 3000 RPM’s = 70MPH.

http://www.ncrs.org/forum/tech.cgi/noframes/read/124316#124332

 

[BarryK]

I could live with that although I want to go a little higher myself, maybe up (down?) to a 3.55 or even 3.36. my car currently has a 4.11 rear in it and while it's fun to accelerate with it and fell that low end jolt when i hit the gas, highway cruising gets tiring very quickly, especially with the louder sound of the sidepipes. at 70mpg I'm around 4000rpm or so it's loud and I keep wishing for that extra 5th gear I don't have to smooth things out. The mirrors are vibrating so much they are almost useless. I'm hoping by next summer I can get the rear in my car switched out.

 

[youwish2bme]

I thought that 2800 at 60 mph was 3:70? At 70 mph I was normally around 3200. Barry I'm glad I'm not the only one with mirrors that vibrate so much that they are about useless..... The 5 spd should help me out a little though.. Dave..

 

[BarryK]

at least you have a 5-speed. I have the orginal 4-speed (M20 I think).
If i'm actually accelerating at the time I don't even waste my time trying to look at the mirrors, they are completely useless!
LOL

 

[Sky65]

70 mph at 2900 rpms.........anyone?

I'm thinking a 3.36. Try this link. I believe stock tires are 27" in diameter.
http://www.quiknet.com/~ke6vut/rpmcalc.html

Sky

 

[youwish2bme]

Sky that's what I thought too.. Dave...

 

[WayneC]

Given:
Stock 205/75x15 tire gets 744 tire revs/mile
2900rpm @ 70mph
transmission is 1:1 ratio in high gear

calculations:
744 tire revs/mile x 70miles/hour x hour/60 min = 868 tire revs/minute @ 2900 engine revs/minute

2900 engine revs/min divided by 868 tire revs/minute = 3.34 axle ratio

 

[Sky65]

The 5 spd should help me out a little though.. Dave..

Yo Dave
Are you putting in a 5 speed? Which one?

Sky

 

[youwish2bme]

Keisler Tremec.. Installed it and just waiting to fire the motor... I'm waiting on fuel line fittings hopefully I'll be able to tell ya how it drives after this weekend... Dave..

 

[Sky65]

Dave
I would like to put in a 5 speed myself. I'm thinking of using a Richmond. Did you consider richmond? Why the KT?

Thanks
Sky

 

[Ron Miller]

70 mph at 2900 rpms.........anyone?

thanks

Sam

Looks like a 3.36, see http://www.drivetraindirect.com/html2/calculator2.html, for example.

rlm

 

[youwish2bme]

Sky it was because of the complete kit. The Richmond is claimed to be a direct bolt in too.. That is if you can fab your own transmission mount. The rest though can probably be done easily enough but with that being said the Keisler is with little to no modifications goes right in. Plus the Richmond 5 spd is a 1:1 not a overdrive if I remember correctly.. Sorry Sam didn't mean to hijack your thread.. Sky email me at david.hitchens@na.biomerieux.com I'll tell you a few things that I learned but I don't plan on airing out here on the forum... Dave..

 

[Sams '66]

I'm thinking a 3.36. Try this link. I believe stock tires are 27" in diameter.
http://www.quiknet.com/~ke6vut/rpmcalc.html

Sky

My tires are 215/70/15

 

[Sky65]

My tires are 215/70/15

I looked on Tire Rack's site and checked a few tire manufactures specs.
http://www.tirerack.com/tires/SearchTires.jsp
For the 215/70/15 one was 26.8, one 26.9 and one 27. Still looks like a 3.36.

Sky