Cole

I swapped my rear gears and I'm trying to find which speedo gears I need for my 700r4. I have 215/65/15 tires. Depending on which method of calculation I use, I find that I need either a 41 or 40 tooth driven gear. Which one is correct?

Superman

try this

http://www.700r4.com/speedocalc/speedocalc.html

Cole

Thanks for posting that link, but I had actually tried that calculator before. The results from it don't match what I get from the calculations in the tech article on this sight or the formulas found on TCI's website.

SSC

700R4.com is correct. Buy the parts from them and save the hassle trying to get GM parts. Back when I had a terrible time finding the part numbers for ther correct stuff, Its not ion thier dsata base anymore (GM dealer's yep 2 of em, Uggh never seen one like that but yea it a valid ## can have it hear by 3:00, Offset housing, new to me, ohh says Ive got this #### on the shelf)

Ovrclck350

I hate that site. 700R4 didn't have ANY of the speedo gears I needed...I almost even bought that damn carrier everyone told me was a "must have." Surprise, I didn't need it.

I found that the gears sold on 700R4 are for cable driven speedometers only. THe ones with the VSS on the side don't use the same gears.



I went to GMPartsDirect to order my speedo gear and it was only $3.09 but I couldn't wait so I went to GM and had it the next day.

Here's my link to my install https://www.thirdgen.org/techbb2/sho...highlight=gear



I believe here's the one for the VSS driven speedo gears (driven gear)
P/N - Teeth - Color
25513042 35 teeth/color: orange
25513043 36 teeth/color: white
25513044 37 teeth/color: Red
25513045 38 teeth/color: blue
25513946 39 teeth/color: Brown
25513047 40 teeth/color: black
25513048 41 teeth/color: Yellow
25513049 42 teeth/color: Green
25513050 43 teeth/color: purple
25513051 44 teeth/color: Dk Bray
25513052 45 teeth/color: Lt. Blue

and here's the one for the cable driven speedo gears (driven gear)
P/N - Teeth - Color
9774413 - 34 - Lt Green
9780628 - 35 - Orange
1359270 - 36 - White
1359271 - 37 - Red
1359272 - 38 - Blue
1359273 - 39 - Brown
1362048 - 40 - Black
1362195 - 41 - Yellow
1362049 - 42 - Green
1362196 - 43 - Purple
9780470 - 44 - Dk Gray
9775187 - 45 - Lt Blue

These are the only drive gear numbers I have

drive gear number 8640517, (red, 17 teeth)
drive gear number 8642620, (gray, 15 teeth)

Cole

Ovrclck350, was the red drive and green driven gear the combination that you went with after the gear swap? I had actually swapped my speedo gears a while back to the gray 15 tooth drive gear and green 42 tooth driven gear (part numbers 8642620 and 25513049 respectively). This combination got me very close. Now the clip on my tailshaft failed and let my gears get chewed up, so I'm getting new ones. When I started looking up part numbers is when I started coming accross conflicting info on which gears are correct for 3.42's. What was the combination of gears that worked for you?

Ovrclck350

That's not a red drive gear it just oddly enough showed up red in the pic. I don't remember which it is...it's whatever came stock in my transmission (1991 Z28 LB9) for the 2.73 rear gears. I used a 45 tooth and the speedo is (I think) 2% off? It's really close.