~ Anno Domini

Hey guys......it's cloudy, there ain't no birds singing and it's raining outside, but it's still a beautful day to be Alive and here's my question please. I have a 1989 6-Speed. I am in Canada and believe it's a Canadian car. If I ever have to replace the stock transmission in my car do I match the gear ratio ? I spoke with someone recently who is selling a 1989 6-Speed transmission and we didn't get into details. He just said that he had a used 1989 6-Speed transmission and it was in good shape. He apparently has a good reputation. The Label in the console of my car has GT7 & G87 and I did a little reading in the Corvette forums and someone posted this:

11-06-2004, 08:28 PM
Z-07 freak
CF Senior Member

6-speed rear axle ratios
early `89s have 3.54 (rpo GH0)
late `89s and `90 L-98s have 3.33 (rpo GT7)
all ZR-1/LT-5s have 3.45 (GM3)
`91-`96 L-98, LT1, LT4 have 3.45 (rpo GM3)

3.42 is used on C5 & C6 6-speeds

Somebody also said that I have very unusual gear ratio for an '89 car. So if I were to buy that transmission from the guy I mentioned, do I have to talk with him and see if the gear ratios on his transmission match my '89 car ? I have no experience with this. Thank you for any words of insight.

JimLentz

See if the total ratio on the transmission tags match.

WVZR-1

ZF ratios are all the same. If his transmission has the TAG on the right side you can maybe 'assume' that it's what this ID information suggests.

This is L98/LT1/LT4 information only - if the tag has information different than this post a snapshot of it.

Length of the input shaft will also ID a ZF as to it's use. An L98/LT1/LT4 ZF will have an input length of 159.5mm and the LT5 a 190.5mm



Depending on what you buy/use for a replacement ZF you only need to match the VSS driven to the axle ratio in the car.

~ Anno Domini

Thank you fellas. Your opinion is of high value to me. I won't deny it, a lot of the information on gear ratios is hard for me to understand, but I know now to see if the transmission tags on the other transmission matches mine. Next time I talk with the guy selling the used transmission I will ask him about this. The Label in the console of my 1989 6-Speed has GT7 and G87, which apparently means I have 3.33 gears. That's where I draw a blank. I think, "What if that other 1989 6-Speed had 3.54 gears. Can the transmission from that car work with my 3.33 gears ?" I wonder if I have to get a transmission from a car that had 3.33 gears like mine, or can the transmission out of 1989 6-Speed with a differential with 3.54 gears work on mine and does it effect performance ?" It is confusing to me, but I am trying to read and learn more on this topic.

WVZR-1

All ZF Corvette ratios are the same. Any correct L98/LT1/LT4 ZF will work. Ratios:



The only thing that requires a 'match' to your rear axle ratio with 3.33 is a change of the VSS driven gear to match the 3.33. With typical 275/40 tires the different VSS driven would be

3.33 - 40 tooth/BLACK

3.45 - 42 tooth/GREEN

3.54 - 43 tooth/PURPLE

You would only need to confirm the driven tooth count on the one you buy and correct that with either a purchase or the transfer of yours.

QCVette

The gears and the VSS can be swapped between all of the ZF transmission. The differences are the tooth count (and color) for the gear and there is a difference in the VSS connector to the body harness.

For example I swapped a '96 with a 3.45 gear and it had the green gear in the 96 transmission. The transmission I bought was a '90 and had the earlier style harness connector and it had the black gear.

I put the green gear into the '90 transmission and swapped the VSS from the '96 into the '90 transmission so it would connect to my '96 car's body wiring. Everything worked as it should.

Good luck.

~ Anno Domini

I'm grateful for your help fellas, I saved the info you gave me and if I have to get a transmission, I will bring up the VSS issue with the seller and mechanic. I have no experience on this, thank you.