I have a 1987 camaro with a 10 bolt rear, 3.42 gears, and 700R4. I swapped out the original one wheel peel gears for 3.42's, and of course my speedometer is off. My wheels are stock 245 50r 16 as well.

So I went to this site http://www.transmissioncenter.net/sp...n_______va.htm

and from what it looks like I need a 17 tooth drive gear and a 45 tooth driven gear? Does that sound right?

I don't want to go order something I am not sure about. i was also thinking about putting in a 145 mph speedometer. That wouldn't make a difference right? Is all I need is to correct are the drive, and driven gears for the newly installed 3.42's?

Thank you very much for looking

 

anyone?

 

sounds pretty close, but i'm going to be lazy and not do the math.
call the guys at Jags That Run and they'll hook you up cheap.
925 462 3619

 

According to the online calculator I used, which calculates it by the tire height and rear gear ratio, with the 17 tooth drive gear, which you should already have in your trans, you would need a 46 tooth driven gear. It said 45.8 teeth, which when rounded up is 46. When I swapped mine to 3.42's, and old tech article here on the site said it's necessary to switch to the gray, 15 tooth drive gear in the trans, so that's what I ended up doing, and with that drive gear, it calls for a 40.4 tooth driven gear, so 40 tooth when rounded to the nearest whole. My speedo was pretty accurate with the 15/40 combo, but if you can actually buy a 46 tooth gear from transmissioncenter.net, then that would be easier since you wouldn't have to swap out the gear on the output shaft of your 700r4.

 

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Thank you Pat Hall. The most teeth gear they sell is 45. Is 17 teeth the the standard for a 700r4?. Do you think I should just put in a 45 instead of a 40/15? It doesn't bother me if it is off by 1-3 mph. And one last question. If I changed my speedometer gauge cluster from the 85 to 145 mph would that make a difference in the gears I should get?

Thanks

 

First off, changing to a 145 cluster will have absolutely no effect on anything, so you're good there. The tech article I read on here quite a few years ago basically said that the red, 17 tooth drive gear was used for 3.23 and numerically lower rearends, 3.42 and numerically higher used the gray, 15 tooth drive gear. Case in point, my car originally had 2.73's and it had the 17 tooth, red gear. I suppose the 17/45 combo would be fairly accurate, but of course if you wanted it "dead-nuts accurate", you'd need to use the 15 tooth drive gear. Also keep in mind that the faster you go, the more off your reading will get. In all honesty, it's really not hard at all to change the drive gear on a 700r4. It's a lot more of a PITA to change out on a T5. To change it, all you have to do is remove the driveshaft, undo the torque arm mount, remove the two trans mount bolts from the center of the crossmember, remove the speedo driven gear assembly, then jack up the trans by the fluid pan using a thick piece of plywood and a floor jack. Then all you have to do is remove the 4 bolts that hold the tailshaft extension on the rear of the trans. The extension housing uses an o-ring for a seal, so you don't have to replace any gaskets either. Once you get the extension housing out of the way, you'll see the drive gear, which is held in place with a spring steel clip. I use a precision screwdriver to release the clip (it goes into a small hole in the output shaft), and while depressing the clip, use a crescent wrench and a hammer to tap/slide the gear off the shaft. Sometimes the clip will break no matter how careful you are, but if it does you can pick another one up at the dealer or a trans shop for a couple of bucks. Btw, a little fluid will leak out when you remove the tailshaft housing, but as long as the car is jacked up pretty level, it won't leak much at all. Anywho, that's how you change it if you decide to go that route.

 

Thank you very much for all of your help and information. I am going to go with the 15/40. The car will be in the air, and I will be under it so I mise well go the extra distance and have my speedometer read accurately.

Thanks

 

Oh yeah, if you're gonna have it up in the air like that, go for it! Should be a cake walk if you have all that room to just stand under there and do it. I've done mine a couple of times since I went with 3.42's for a while and had to put in the gray gear, then switched to 3.23's and had to put the red gear back in, and each time I did mine it was laying on my back in the driveway. Having a shop lift is a godsend for that job!

 

Make sure you have the right VSS or cable gear housing for the driven gear you are installing. The 34 to 39 size gears is one VSS/cable housing and 40 to 45 gears is the other VSS/cable housing.

Jerry

 

Oh sorry for not clarifying that... I will be on my back to. Just meant while I had it on all four jackstands go the extra distance. I wish I had a lift. I would be under my car even if I didn't have to just to look for something to do. Jerrywho said I would need a new vss/cable housing for 40-45 gears. My car had originally 2.73's. Does that mean I have to get a new housing?

 

You know, I've never really understood why there's two different sleeves myself. When I got my 3.42 speedo gears at the dealership, they sold me the other sleeve too. I've compared both sleeve assemblies sitting side by side, and I couldn't see a single difference. Then again, maybe they sold me the same one I already had. Lol. Whatever the case, click on the link I'm posting here, and the two sleeves are just a little ways down on the page. Further down on the same page they also list two different VSS units as well for the 90-92, electric speedos. One sleeve is for 34-39 tooth gears, and the other one is for 40-45 gears. http://www.transmissioncenter.net/sp...n_______va.htm

 

Okay thanks. From what it looks like I will need a new housing. Quite expensive for a little piece. But I need it. Thank you for your the help the whole time

 

You might still be able to get an original housing for cheaper through a Chevy dealership. The advantage to the more expensive one from PATC though is that it's made out of aluminum. The original GM housings are plastic. I've never had a problem with the plastic one, but the aluminum ones are nicer.

 

That's a good idea. I will go to my local Chevrolet dealership and ask about the housing tomorrow. So they make plastic housings for 40-45 gears? Thanks man.