I swapped my rear end out from 2.73s to 3.23s, and I ordered the speedo gears from bowtieoverdrives, and they sent me the wrong parts. They sent me a 43 tooth gear and housing, but it was for a mechanical speedometer - mine is electric. So I called them and they dont have the 43 tooth cone gear like I need, but they do have a 42 tooth. So basically I would be using 17 tooth gear with a 42 tooth gear for a 3.23 rear end. Will this be close enough to correct my speedometer? How far will this be off percentage wise? Thanks for any help!

Chris

 

Speedometer Gears, Speedometer Gear, Ford, GM, Dodge 700R4


i bought mine here they have everything and a chart ot help you out, check them out

i believe you have the wrong gears regaurdless assuming you have stock 26" tires you should need 18 drive 45 driven gears, yours are for taller tires and 3:42 gears. so you should go out and smack someone :P

 

Thanks for the advice, but using the calculator at bowtieoverdrives and at the site you gave me, I got the same results: 17 tooth drive gear, and 43 tooth driven gear. This is for 3.23s with 26" tires (245/50/16). So it seems like my gear combination is right. Anyone else know how close it will be with a 42 tooth instead of 43?

 

you will only be off by 1 tooth, the difference in speed will be marginal, if noticable at all. besides, the cone gear is easy to change so if you find the right one later and want to swap it its a piece of cake

 

Well I don't "know", but I "know" how to calculate it.

You'll be 1/43 off, in the direction of reading higher than reality. Which is about 2¼% or thereabouts. i.e., your speedo will read about 61.25 when you're really doing 60.

Which is less error than what you'll experience as your tire pressures change from heat; or as the tread wears; or when you buy a different brand of tire.

In other words, close enough that further futzing around with it is pointless.

Measure with a micrometer, mark with spray paint, cut with dynamite.

 

Makes sense - thanks a lot for the help guys.

Chris

 

I did the exact same gear swap in my 89 RS (2.73-3.23). The correct factory GM gear for the sending unit is dark gray in color and has 44 teeth. You should already have the correct red color 17 tooth gear on the output shaft of the trans, all you need to get is the gray gear. I snagged the gray gear from the 700r4 that was in the same 91 GTA that my 3.23 rear axle came from, so I know it's correct for that ratio with 16" wheels and 245/50 tires.

 

Crap, they already sent the 42 tooth gear. They had 44 tooth gears available too, just not 43's. I wonder why their calculator said i needed the 43 tooth. I guess I'll just put the 42 tooth in and see how close it is with somebody else's car.

 

well with all the different variations of drive/driven gears there has got to be more than 1 way to get quite a few combos

 

I got the 44 tooth count by checking the FAQ section here, so that may or may not be totally accurate. I do know for a fact that the driven gear is dark gray though. I don't know how bowtie overdrives identify their different gears, but the gm ones are color coded according to how many teeth they have. Since it's already in the mail you might as well go ahead and try it and see how close it is. If it ends up being off by quite a bit, you can get the gray gm gear from your local chevy dealership. I ran 3.42's for a while too, and the parts guy at the chevy dealer hooked me up with the proper gears for that. That combo requires a gray output shaft gear and a yellow driven gear. At least we can still get gears for the 700r4's easily. Speedo gears for the T-5's are a whole different story!