I'm pretty new to the whole gear swapping stuff.On an automatic transmission 1991 3.1 V6 Firebird.I have a few questions

1.Whats on there now?

2.Whats the best setup for my ride?

3.They give better low end and take away top correct? How much top end is taken away? Its pretty crappy already once the car hits 4th...

4.What are the downsides? How can I adjust the speedo/odo after a gear install?

5.Finally,What exactly do I need? Just the gears? (link to exactly what I need would be awesome) How much do they cost to install?

 

Well I can tell you that you have 3.23 gears.

In my 5-speed I have 3.42's and love it.

 

3.1 with auto have 3.23
3.1 with 5sp have 3.42

It is to make them "the same".

As for whats best.. What do you mainly use the car for?


I was finding between 250-600 to have gears and posi installed. Hince, why they are not installed yet

 

I suggest 3.73's be the highest gears you get if u plan on driving your car on the street. If your going all motor i suggest 3.73's, but if your going with turbo like many guys are doing now than i think 3.42's are your best bet. Also im pretty sure u have to reprogram the computer chip when u get new gears so it will make correction to the speedo.

 

One Idea is to go out to a junk yard and find a car with a v6 and a 5-speed, they're all over out here in California, don't know about your area. Pull the back cover off and check out the gears and spin them to see if they are easy to turn(checking the bearings, make sure there isn't a lot of play and that they aren't wasted). Buy the rear end, and stick it under your car. Change the fluid after 500 miles, then call it good. You'll have 3.42's for like 50 bucks.

 

i love my 3.42's

can't go wrong with them, just gotta add a posi

 

the 3.42's are good up to about 85 but after that the engine just doesn't have enough to pull them any faster. i am going with the 3.73 if not 3.83's for more acceleration. my speedo isn't controlled by the computer, and i don't know if the make the new gears for the tranny to correct the problem

 

They do make the new gears to make the trans and speedo correctly coordinated. GM even carries them at the dealerships. There's a tech article on here somewhere with the part numbers and other info you need.

 

awesome, now i just wish that i could find it!

 

Your vehicle shold have an electric speedo.
I beleive 1985/86 was last year for cables.
That said, Go to dealer and tell him your combination.
Rear ratio
Tranny
He'll sell ya what ya need.
Remove tranny tail ahsft & make sure you do not ruin the clips.
Seriously?
IF you suspect your sppedo is off, go for ride with someone else in car besides ya & do a "test".
That's easiest.
Or find highways with measured mile marks for testing.
Determine what's going on from those results.
But dealer has the right plastic gear and correct parts. Buy the guy a soda & ask him for the illustrated parts description and take home for future reference.

 

actually karl i got the mechanical, in fact i just had to replace the cable and the insturment pannel. i will take your advise for the correct tranny gear to get me the correct speedo calibration.

 

I still have the mechanical one too. i think the birds got the electronic ones in 87 and the camaros got it in like 91 with the 3.1 I think. Not 100%. Someone should search for it. I'm too lazy and just don't care. lol

 

Do the drive test first.
You should be off by about 3 MPH or so.
More take the knowledge and judge that the other car may also be off, too.
BUT I SUSPECT the newer the test car, the "better the results".
Milage markers on freeway is the sure thing test.
Go speed limit and if ya get to that number "right there" in a mile ya also good.
"Tires" and changed "tires" can factor in also.....
Freeways are exaclty correct in their markers.