I've been on here for @ 2 hours, and this is what I have fiqured out.

Current setup Stock except for tires.
91 RS 305 V8 (LO3)
VSS RPO (D8N)
Gear, Speedo Driven RPO (D3W)
Axle Ratio 2.73 RPO (GU2)
Auto 4 speed trans, THM700R4 RPO (MD8)
I'm running 245/50/16 tires. Came stock with 235/55/16 tires RPO (QMT)

I bought a 3.42 rear off a 91 or 92 camaro, guy didn't know for sure what year it was originally from.

According to my research, I could change to a yellow 41 tooth p/n 25513028 and a gray 15 tooth p/n 8642620.

Now am I correct that I currently have a 17 tooth and could just replace the VSS gear with a 45 tooth p/n 25513052 because they don't make a 46 tooth gear. Is this more or less accurate then changing both gears
Also does anyone have for sale any of these parts. Including the clip.

Oh, what about the sleeve, where is it and do I need to change that too, if so what part #. Do I need a different VSS??

Also I know I should expect worse fuel economy, but what happens after the change to 3.42s to the RPMs at highway cruising, and is the top speed decreased?

While I'm posting, How benificial is it to put a stainless brake line in for the rear brakes while I'm changing the rear? Is it worth the upgrade for the rear brakes. There still Drum type.

Please Help a New Guy out!!!

 

i can only answer your last few questions, myself, i Upgraded from 2.77 to 3.42 gearing. it was worth if for the street. at the track, it made -0- difference. probably due to the worse 60foot. on the highway i cruise about 2300 rpm at 65mph.

 

If you drove your car the exact same around town and didn't take advantage of the added torque from the gear swap, your city mileage would probably improve. Mine did when I went from 3.08s to 3.73s. In these heavy V8s powered cars, lower gears around town seem to help mileage.

I did several things at once to mine, but the 3.08 to 3.73 gear swap was worth almost 1/2 second and NO trap speed difference.

 

when will they make centrifugal gearing for our rearends?

 

Ok, so what i have learned is that 17 w a 45 will be off the wrong way, cause I would need a 46 tooth. So I need a 15 and 41 to be on the safe side because you can't buy a 40.5. Is this correct. Or do I get 16 and 43, calc came up 43.2?

 

I'm running a 17 and a 45 and its close enough to not know the difference..... I would guess less than 2mph off @ 60mph.

 

Here is what you need:

-15 tooth drive gear part # 8642620 list price $6.24
-41 tooth driven gear part # 25513048 list price $6.24
-new sensor part # 10456089 list price $46.19

I don't know why but they list a different sensor for that gear.

 

thank you so much, i've been looking for the part # forever. I guess I'll check with some of the techs and see about the sensor. I've heard that there are 2 different ones. One for < 40 teeth, one for > 40 teeth. But I have not checked with the techs.

Kris

Oh, I work at a chevy dealership.

 

stock should be 17 tooth and a 36 i believe.

3.42's should be 15 and 41.

i have 3.27's and using the 15/39 setup and it seems close. 3mph off at 100mph probly i'd say. so 41 should be the right part for the 3.42's.

but i think the speedo gear housing needs changed out. there are housings for the 34-39 tooth gears and then a housing for the 40-45 tooth gears.

bowtie overdrives
http://www.bowtieoverdrives.com/cata...BCAT&CATID=DA2

 

I swapped to 3.42 from 2.73 - used the 15/41 combo - haven't checked it against a known correct speedo, but it seems to be there.

I didn't understand about the different housing - and the damend things are expensive - I kept my same housing, don't seem to have any problems - the gear sizes seem to be the same, just more or less teeth on different gears. But again, I only have put maybe 300 miles on since the speedo gear swap, but it ain't broke, so I ain't gonna fix it!.

 

I used the same housing that the red 2.73 driven gear came on with zero problems.

 

....and there's no one in your parts dept. that could figure this out?

As far as the housings go, I've used the wrong one on an 88 TA that was swapped from 2.73 to 3.45 gears and it hasn't had a problem yet!! You might want to get the gears first and see if it works. They're cheap enough that if you do have a problem you can get another set and the "correct" sensor later.

 

they are not very helpful to find part #. they are very busy, they do like 60K a day just out of the back counter. The front counter guys are busy too. plus they have a bad attitude about the sales dept. don't know why though. they don't make as much commision on an employee sale as they do for reg customers.

 

You need the gray 15 tooth gear for the output shaft of the transmission, and the yellow 41 tooth gear for the vss. These are the gears I used in mine when I switched from 2.73 to 3.42, and the speedo was pretty accurate. One of the parts guys at the chevy dealership looked them up for me using some chart he had on the computer there. Right now with 2.73 gears, you should have a red 17 tooth gear on the trans output shaft, and a red gear on the vss as well.