700R4 gearbox on an 82

Sat 23 Jun 12 20:06

700R4 gearbox on an 82

Anyone know? On an 82 with standard 700R4 gearbox, what should the revs read at 60mph, assuming all is working as it should? I am getting a reading of around 2000 rpm. I am pretty sure this is about right with the lockout working but thought I would just check.

Thanks

Sat 23 Jun 12 20:30

Re: 700R4 gearbox on an 82

Depends on the final drive Adrian. That's 30mph per 1000 rpm which sounds like more revs than I would expect at 60mph.

Obviously tyre diameter affects the gearing too but my 93 used to run slightly over 80mph at 2000 revs and that was with a ridculously high rear axle ration at 2.59:1 (yuk!)

93 coupes with the optional 3.07 rear gear get 62-63 ish mph at 2,000 rpm so if your 82 has a 3.07 or similar I guess it's the right ballpark.

Have you bought an '82 Adrian?

Malc

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No corvette at present.
2005 Mustang GT 5-speed

Previous Corvettes:

1984 red Crossfire auto
1993 red LT-1 auto
1990 black Callaway Twin Turbo 6-speed
1996 CE LT-4 6-speed

Sun 24 Jun 12 12:59

Re: 700R4 gearbox on an 82

http://www.angelfire.com/fl/procrastination/rear.html

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Corvette 1977 coupe
She LIVES
Now 383ci

Sun 24 Jun 12 19:43

Re: 700R4 gearbox on an 82

Thanks for the replies so far.

Assuming that the car has the standard axle ratio for an 82, then it is 2.87
So the calculator provided by 'Wev' produces 38.5 mph per 1000 revs based on a 0.7 top gear ratio. Therefore 60 mph should be just over 1500 rpm not 2000 rpm.

I am still working on either the lock up not working or maybe the rev counter is a bit out?

I am hoping that someone with an 82 has the answer.

Tue 26 Jun 12 10:30

Re: 700R4 gearbox on an 82

Hi Adrian - Have you got an 82 now? You haven't bought your old one back have you? (I saw it for sale again recently ) I guess you know you can get the diff ratio from the stampings on the base of the diff case?

--------------------
Stephen J Irons
CCCUK Lifetime Member
Corvette Club France
Corvettes of Southern California
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Red Corvettes Have More Fun!


The "Born-Again Greenies" are killing the planet! It's time to tell the world the Emperor is naked!

Tue 26 Jun 12 20:09

Re: 700R4 gearbox on an 82

Hi
I have a standard 82 will try and take it out in the next couple
of days and let you know what mine shows at 60 mph

Regards derek

Fri 29 Jun 12 14:31

Re: 700R4 gearbox on an 82

Just read a 'car and driver' old road test and according to that it stated quote 'An unbelievable 1400rpm at the legal limit' Now given this is a yankee report I expect he meant 55mph as this was the limit from '74-87 and the report is dated march 82.

So it does really sound like your lock up is not coming in. I would have expected to see around 300-500rpm drop when the lock up comes in under light throttle.

You should clearly see a difference on the rev counter when it activates and you should be able to feel the difference as increasing the throttle wont significantly raise rpm until the car speeds up. If you have any sign of it still reving up without speeding up then it aint working ! Most likely cause is either the solonoid unit in the box or the wiring to it. It's not likey to be the converter clutch.

It goes without saying that you should get these readings with stock tyres of either 255/60/15 or 225/70/15's

Jon

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82 Corvette C3 - Just needs waxing + total restoration!

Sun 01 Jul 12 13:18

Re: 700R4 gearbox on an 82

Stephen - no not my old one but a very nice Collectors Edition. I didn't know about the stamping on the base of the diff so thanks for the tip.

JohnnyBlue - I did read that Car and Driver article and came to the same conclusion as you have. I was hoping that someone else with an 82 could confirm it. I will then be looking at the solonoid, wiring, ECM etc. One thing that I do know is that the ECM has a Hypertech chip in it so that will need checking out as well.

Derek - thanks for the offer to help, it would be good to know the results of your test.

Sun 01 Jul 12 21:04

Re: 700R4 gearbox on an 82

Hi Adrian,

my 82 is a totally standard car, just taken it out and checked speed both on speedo and sat nav.

At 60MPH - around 1600rpm
At 70MPH - 2000rpm
At 80MPH -2100rpm

Hope this helps.

Regards,


Derek

Sun 01 Jul 12 21:49

Re: 700R4 gearbox on an 82

Hi Derek

That confirms what I thought. I need to find out why the torque converter lock out is not working.

Thanks for your help

Adrian