Speedo Gear Question
Thread Starter
1st Gear
Joined: Oct 2004
Posts: 1
Likes: 0
Speedo Gear Question
hey everyone,
I am new to the forum so bear with me. I have got a 91 corvette I swapped out the auto matic for a stock zf 6 speed and changed the 2.59 rearend to the 3.07 out of anouther corvette. I have stock rims and tires. My question is what color or what do I need to do to get my speedometer to read correct. Hope someone knows the answear.
Thanks
I am new to the forum so bear with me. I have got a 91 corvette I swapped out the auto matic for a stock zf 6 speed and changed the 2.59 rearend to the 3.07 out of anouther corvette. I have stock rims and tires. My question is what color or what do I need to do to get my speedometer to read correct. Hope someone knows the answear.
Thanks
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
I dont think the 3:07 and the ZF 6 speed will work unless you havea green driven gear and get a RED drive gear and have it bored out larger to fit the ZF ouput shaft.
Bill at www.zfdoc.com was abotu to make some of these but I could not wait and bought a www.dakotadigital.com speedo calibrator.
I have the ZF with the 3:07's too, at least for now.
Bill at www.zfdoc.com was abotu to make some of these but I could not wait and bought a www.dakotadigital.com speedo calibrator.
I have the ZF with the 3:07's too, at least for now.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Is that the stock trans for that year car? You probably don't know what the donor car had for gears. You need a red, 17 tooth, drive gear, pn, 8640517. A green, 42 tooth, driven gear, pn 25513049. And a 10456089 VSS, for a stock '91 6 speed. The VSS goes with the driven gear. If the one in there now has 42 or more teeth, the VSS won't have to be changed.
RACE ON!!!
RACE ON!!!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by ld85
Just remember, the red gear has an ID that is too small for the output shaft.RACE ON!!!
Last edited by CFI-EFI; Oct 4, 2004 at 10:04 PM.
Team Owner
Joined: Jul 2004
Posts: 28,358
Likes: 3,253
From: Hartford WI
So what do you do when you go from a 3.07 to 3.45 or 3.54? Which VSS do you use? I know you have to change the driven and driven gear to say a 15 tooth drive and 41 (based on calculations) driven but what else?
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Melting Slicks
Joined: Jul 2003
Posts: 2,384
Likes: 124
From: Reno/Sparks Nevada
Do you want a part number? If you have a 3.07 reuse the sensor and install new gears in the trans and on the sensor. I hope that's what you're asking. I have a part number somewhere. There are 2 numbers, one was superceded by the other.
Team Owner
Joined: Jul 2004
Posts: 28,358
Likes: 3,253
From: Hartford WI
Originally Posted by MrRenoman
If you have a 3.07 reuse the sensor and install new gears in the trans and on the sensor. I hope that's what you're asking. I have a part number somewhere. There are 2 numbers, one was superceded by the other.
Melting Slicks
Joined: Jul 2003
Posts: 2,384
Likes: 124
From: Reno/Sparks Nevada
Here's a link to a popular site.
http://www.corvetteforum.net/c4/vett...Gearshtm.shtml
Here's the part number off my new speed sensor. The number I pulled out of my old 84-87 Illustrated Parts Catalog was superceded by this one.
25007308
BTW, if you have a '91 it looks like it changes part numbers, I didn't realize this til I looked at the web site, hope it helps.
http://www.corvetteforum.net/c4/vett...Gearshtm.shtml
Here's the part number off my new speed sensor. The number I pulled out of my old 84-87 Illustrated Parts Catalog was superceded by this one.
25007308
BTW, if you have a '91 it looks like it changes part numbers, I didn't realize this til I looked at the web site, hope it helps.
Last edited by MrRenoman; Oct 4, 2004 at 11:06 PM.
Doh! Sorry! I crack myself up sometimes. Glad I can laugh at myself.
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
The only way you can get a match exactly with the ZF and a 3:07 rear gear is to take the RED gear and fill the voids in the sides of the injection molded RED gear with JB Weld etc, let it dry then bore it out on a lathe so the ID will fit the larger output shaft of the ZF. The ZF did not come with a 3:07 option and the RED gear is for the 4+3.
Call Bill at ZFDOC and he will tell you the same thing.
Or you can go to www.dakotadigital.com and buy a speedo calibrator for $75 and make it nearly perfect.
Call Bill at ZFDOC and he will tell you the same thing.
Or you can go to www.dakotadigital.com and buy a speedo calibrator for $75 and make it nearly perfect.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Another way to go is the 15 tooth gray drive gear, you probably already have, a 37 tooth, red, driven gear, pn 25513044, and a 10456088, VSS. I have yet to find a 17 tooth drive gear for the 6 speed.
By the way, the red 17 tooth drive gear fits the 700R4/4L60, as well as the 4+3 transmission.
RACE ON!!!
By the way, the red 17 tooth drive gear fits the 700R4/4L60, as well as the 4+3 transmission.
RACE ON!!!
Team Owner
Joined: Jul 2004
Posts: 28,358
Likes: 3,253
From: Hartford WI
Originally Posted by CFI-EFI
Another way to go is the 15 tooth gray drive gear, you probably already have, a 37 tooth, red, driven gear, pn 25513044, and a 10456088, VSS. I have yet to find a 17 tooth drive gear for the 6 speed.
By the way, the red 17 tooth drive gear fits the 700R4/4L60, as well as the 4+3 transmission.
RACE ON!!!
By the way, the red 17 tooth drive gear fits the 700R4/4L60, as well as the 4+3 transmission.
RACE ON!!!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by aklim
MD8 with P275/40ZR17 Tires 3.07 8640517 Red 17 25513049 Green 42 10456091 is the combination I currently have. Just wondering if I could simply switch the drive to 15 and the driven to 41.
RACE ON!!!
Team Owner
Joined: Jul 2004
Posts: 28,358
Likes: 3,253
From: Hartford WI
Originally Posted by CFI-EFI
For the 700R4/4L60 the 15 tooth, gray, drive gear, is 8642520. MY books show that is all you HAVE to change. My books don't show a 41 tooth driven gear. I DO show that the 42 tooth driven gear and the 38 tooth driven gear use different VSS's, but I don't know where the break is. In other words, I don't know if you have to change the VSS for a 41 tooth driven gear, or not. You can try the 41 toother with your VSS and see if it goes together properly. Upon further review, my book calls for a purple, 43 tooth, driven gear (25513050), with those tires. That gear WILL work with your present VSS.
RACE ON!!!
RACE ON!!!
Heel & Toe
Joined: Apr 2019
Posts: 16
Likes: 0
Being new to this forum, may explain that I wouldn’t know that a link would be so old and still visible. As far as your comments, totally unnecessary, but you can continue to hide and be derogatory. People like you give good corvette owners a bad name. Enjoy your day.
