So I got my 91 firebird a couple weeks ago. I wad told it needed a speed sensor. So after doing some research and calling the dealer my car came factory with a manual tranny and someone switched it out for a 700r4. So what can I do to get the speedo working properly? Dealer said I have the 3.42 rear end and It was taken to a tranny shop by previous owner and I spoke with them and they said something about the gears in the tail shaft of the tranny. Just looking for some guidance to get it fixed. Thanks in advance.

 

http://www.jagsthatrun.com/V8-chapte...ed-Sensors.pdf

 

Isn't that more directed towards engine swaps? I'm guess I'm still kinda confused on the whole situation

 

Have a look here:

http://www.transmissioncenter.net/sp...n_______va.htm

 

Yeah I've been there I have been searching all over trying to find what I had from the factory so I can then figure out where I need to be for the 700r4. Originally with the manual it had the 7 tooth purple and a 19 tooth driven. So now I just need to figure out where I need to be for the 700r4.

 

I assume you've run the gear calculators? Give them a call. I did and they seemed like they knew what's going on. I'm hooped the other way. I went to a T5 and need a brown 18 Tooth driven gear. Which is nowhere to be found.

 

You didn't say what parts it has (or post pictures) or tire size.

http://www.transmissioncenter.net/sp...n_______va.htm

You need #54X. Speedometer drive gear, comes in 15, (you need 15)
and
#55XX. Speed sensor for above 40 to 45 tooth driven gear.
and
#55. Driven gears for gear driven electronic speedometers (you need 41 or 42 depending on tire size.)




A 1991 Firebird 700-R4 has a speedo gear-driven VSS and needs the proper gears (drive on the output shaft and driven on the VSS) to be accurate.

 

I don't know what parts the 700r4 has inside I was just told to find what gears the manual had from the factory and go from there which I posted above what it had it. So those parts are what I need even though the 700r4 wasn't stock in this car? And if has 16 in rims on it now but they aren't factory wheels

 

The lazy way is 19/7, x15=40.7, so 41:15. Part numbers are in the sticky. How to calculate it more accurately is in the other sticky.

 

Still any easy way to find / get what you need, aside from the gears.

 

Wheels don't matter, tire circumference matters.

 

245/50/16 is what's on the car at the moment

 

Now you can jack the car up, remove the retaining bolt and see what gear is in there.

Fingers crossed you have a 41 or 42 and can just buy the 15t drive gear for now.

 

I appreciate all the help. I was slow to understand what all I needed to get. Hoping tomorrow to check and see what i have and order parts. So 15t drive and 42 gear driven is what I need.

 

I have an opinion on the 41 vs 42, but I don't feel like cross referencing tire sizes right now. That and more wrench, less internet.

 

Well what's your opinion lol

 

Most 700R-4s came with 17s or 18s. If you have a red 17, then a 45 should be close enough, if you can find one. If you find you have a 19 tooth drive gear, I'll trade you a new 15 for it, I'll pay both shippings, if you can remove it without any damage. They like to crack / split.

 

So I was told 15/41. Your saying 17/45 and the transmission center chart is saying 17/45.

 

With 17:45, less chance of a speeding ticket, you'll be going slightly slower than what your speedometer shows.
Using the info in the sticky, it would be 15:40. But if you correct for tire loading ( I don't ) then my math shows 15:41.46.
No matter what we tell you, you still must decide what's best for you.
Get under there, see what's in it now. Changing dive gears in-car is hell even when you do try to destroy the old one.
You can change which style of VSS and just get one of those little inline corrector boxes from transmissioncenter.net, that's easy, but not cheap.