I just got a WC T5 from a junkyard, pulled the old T5 out and put the new tranny in, everything is workin good, but the Speedo seems to be 10mph off. The car is a 91 Firebird Lo3. I heard TPI cars got the same tranny with diff ratios, the tranny i got from the boneyard was already pulled all they knew was it came out of a 5.0 V8 gm car, it had the electric speedo conn. I think it may be out of a TPI car any way to tell?

 

The speedometer is not "10 mph off". That is, while it might be "10 mph off" at some one particular speed, it's not "10 moh off" at 0, "10 mph off" at 30, "10 mph off" at 90, etc.

Think of it as a percentage: it's 15% off, or whatever. So it's 3 mph off at 20, 4½ mph off at 30, 6 mph off at 45, 9 mph off at 60, etc.

Take your old speedo gear out of your old transmission and put it in the new one.

Doesn't matter what kind of a car it was out of, in that respect.

 

Not that it matters for the problem athand, but just so you know, in case you notice a difference at cruising speed... yes, there was a difference between the ratios of the TPI and TBI trannies, but only 5th gear: .73 for TPI, and .63 for TBI.

 

how did you change it from electric speedo connector to cable?

edit: nvm i thought you said you were putting it in an 86... i guess i was thinking about the previouse thread.