Hello All,

I currently have a 3.42 posi in a '91 Formula with electronic speedo.
I have a set of 3.73s I am going to install in same car next month.

I am trying to find out if if anyone knows:

1) what the speedo gear combos are for the current 3.42 and

2) what the speedo gear set combos need to be for the 3.73s to keep an accurate speedometer ?

thx in advance,
RP.

 

It will be the same drive gear.

Check your odometer. If it's accurate, then look at the driven gear you have now; count the teeth; get one with as close as possible to (3.73-3.42)/3.42, which is about 9%, more teeth.

 

Here is a great link for speedo gears and how to figure which ones will work for you. It is near the middle of the page on right.
http://www.sallee-chevrolet.com/Chev...tallation.html

 

www.700r4.com there is a calculator on their site

 

I've checked the tech notes, done some searches, perused web pages.

There seems to be a diff between drive/driven gears on autos and T5s. Can anyone comment on this ?

eg: 15/41 on an auto vs. 9/22 on a T5 ???

Lost, confused,
RP.

 

Yes, the auto gears and stick gears are completely different, not interchangeable.

 

ttt.

I am stuck the search engines are still down and I need to know how many teeth in the driven gear for my existing 3.42, and also for the 3.73s I am swapping in. Can anyone help out ?

thx,
RP.b