700-R4 / SPEEDO GEARS AND DIFF QUESTIONS

[GP4U2NV]

As in my other post. I purchased a swaped mut of a 1983 Buick Regal.

I am having problems with the speedo. It reads really really slow. 47 mph is actually 72 miles an hour by gps.

I know that it is a 700-r4. I know the rear end is stock housing limited slip. The orginal engine was a 4.1 liter F/injection. The tires are sized 255.40.17.

I did the rear end thing, where you mark the pinion and rotate the wheel one turn.

I counted 2 and a little less than 1/4 turns. I was guessing 2.23?

I need the speedo correct to avoid the slow speed zones when there is no other cars to compare to.

Please help.......

 

[80ELCAMINOFLAKE]

Hey, hows it going....

heres the website where i got my speedo gear info...they are pretty good....but u need to know your rear end ratio/wheel size/and transmission type....with all those three things they can tell you what size speedo gears you need for drive and driven..i just changes mine like 1 wk ago...after u do it make sure your housing with the rubber bushing is good...im having little leaks from there...and i now its becuase i probley didnt put it in right.lmao


http://www.transmissioncenter.net/highperf700r4.htm

hope this helps

 

[Pbngem]

You very probabaly have a 2:29 axle ratio. The 2:29 was common in the G body. Other ratio's in the G body were 2:41, 2:56, 2:73, 3:08, & 3:73.

As in my other post. I purchased a swaped mut of a 1983 Buick Regal.

I am having problems with the speedo. It reads really really slow. 47 mph is actually 72 miles an hour by gps.

I know that it is a 700-r4. I know the rear end is stock housing limited slip. The orginal engine was a 4.1 liter F/injection. The tires are sized 255.40.17.

I did the rear end thing, where you mark the pinion and rotate the wheel one turn.

I counted 2 and a little less than 1/4 turns. I was guessing 2.23?

I need the speedo correct to avoid the slow speed zones when there is no other cars to compare to.

Please help.......

 

[GP4U2NV]

Where the 2.29 a limited slip?

 

[Pbngem]

Not sure on that one. I've never come across a factory GM 2:29 with limited slip, but I've seen them in 2:73 (elcamino) & 3:42, 3:73(monte carlo) There were likely other limited slip differentials ratios available from GM between 1978-88 also.quote="GP4U2NV"]Where the 2.29 a limited slip?[/quote]

 

[GP4U2NV]

The reason I am asking......

It is a posi / limited slip.

I proved it 2 ways.

1) Burn outs both wheels ( i know lol)

2) I rotated the tires and the other wheel rotates the same way.

 

[80ELCAMINOFLAKE]

did u found ur right gears? any updates?

 

[GP4U2NV]

I did but I have not picked them up yet

 

[GP4U2NV]

For additional information to increase the board knowledge.

The 700r4 - speedo gears both driven and drive are available for purchase right from the GM dealerships.

You can use this site to help calc. your needs with limited information
http://www.700r4.com/speedoCalc/speedocalc.shtml

I purchased a 19 driven and 34 drive. I could have waited until i knew what the drive was, but I fiquired better to start new with both with a low purchase price of $11.oo for the pair.