I swapped my drivetrain out to a 1991 Z-28. The dash is out of a 91 RS. I've got a 1991 Z-28 140 cluster in it. For some reason the speedo is like 10 off. Any ideas?

 

did you swap trannies? if you took a tranny out of a car with diff rear gears your speedo will be off. Im in the midst of a dash swap and will have a very inaccurate speedo. Im gonna try dakota digitals calibartir thingy thats like 75 bucks. Check their website for info. Im gonna make a post in the product review board for anybody whos used one of those.

 

why not just swap the speedo gears in the trans that match the correct rear?

 

he could do that, but unless the gear in the transmission itself is changed there will be some innaccuracy.

if you do just use the old speedo gear to match your rear, count the teeth on the removable gears on each tranny (or they might have a number printed) and the difference should be your inaccuracy, if ive been correctly informed (the guy whotold me this worked at aamco, but this was accurate on my car when i swapped trannies)

 

its pretty easy and less $ to change both the drive gear in the trans and the driven gear. Then it should be accurate. try here. http://sethirdgen.org/vss.htm

 

holy crap, that article is extremely helpful, they list the part numbers for exactly what i need! I didnt think i could get 3.73 electric speedo gears for a 700r4 from gm. That means i dont need that dakota digtal thing. Thanx for posting that.

 

I too would like to thank you for that site...

Your avatar pic is GREAT

 

Good luck if you have an electric speedometer. I changed gear ratios and now my speedo is off. I was told by my local GM dealers that the speedometer gears I want are discontinued. Every other place I searched like: SLP, Third Gen Resource and Bowtie Overdrive all advertise gears for 700r4 electric speedometer but told me they dont carry the parts when I tried to order them. I plan to try the Dakota Digital electronic ratio adapter since it is the cheapest solution I found so far.

 

Thanks for the help hopefully I can get it to be accurate.