Swapped a 145 speedo in my 88 sport coupe. Test drive revealed it was reading way fast. Any suggestions on how to fix this problem? Does it matter if it comes from and auto or manual car?

 

Welcome to TGO, PlaneJane.

No.

Perhaps something here:

https://www.thirdgen.org/forums/inte...eedo-woes.html

JamesC

 

Looking for something a little more specific to my problem. I appreciate the help, but has anyone run into this problem and how did you fix it?

 

the 145 mechanical speedo is a direct swap into the cluster, no other changes needed

I see you've got a 9 bolt with 3.27 gear. Was the speedo drive gear in the trans swapped to match? and was the old speedo reading correctly?

 

Rear came from a trans am and the speedo came from eBay.

 

Sweet. Didn't know that.

Were the speedometer gears in the transmission tailhousing swapped out for the proper gears when you swapped to the 3.27?

 

The car the rear came from was an auto and mine is a stick

 

As I mentioned in the above link, a rear change, if the ratio is different from the original, will affect the speedo reading.

JamesC

 

It was still off with my original rear and that had 3.08s.

 

Auto or manual makes no difference.

If it was off with the original rear end, it may be bad. Everything outside of the speedo unit is the same for either the 85 MPH speedo or the 145 MPH speedo, assuming both were stock mechanical units (round face).

Try the original speedo and see how it reads.

Post a pic of this 145 speedo.

 

88 sport coupe V6 likely came from factory with 3.42 rear

At least mine did.

 

What is you GUx RPO code?

 

I'd have to go look later for the rpo code. Its a tbi with a stick

 

And has 115 MPH speedo and its spot on with the original rear

 

I'd guess the 145 speedo head is faulty.

JamesC

 

Anyone know of a good place to get it rebuilt? I got it cheap cause to cause the trip is broke

 

Don't assume anything, & don't waste time chasing codes.

Verify what the the rear end gearing is, then remove the VSS and verify the speedo DRIVE and DRIVEN gears that are currently in use. This should take no longer than 15 minutes of your time. Once you are SURE that these are all MATCHING parts,... then begin to think about the cable or speedo head as possible problems.


I *think" the 3.27 with T5 should be a red 7 tooth DRIVE gear and a brown 18 tooth DRIVEN gear. Double check to be sure !

 

or maybe a 145 overlay was placed on an 85 unit

 

Car is an 88 plane jane. 305 tbi with a stick. If the rear that was in it was original to the car, gears are 3.08s. Its possible if the guy I got the speedo put the overlay on a 115 speedo cause doing like 80-85 in the car the speedo was reading 120.