What would make my convertor try to lock up at 30 MPH while going thru town? It's a '97. My speedometer was reading like a tach yesterday (as soon as I took off from a stop sign and was barely moving it would read like 40 MPH and by 60 MPH it was reading 80 MPH and bouncing all over.

The speedometer fixed itself but could that and the convertor be related? Maybe the VSS? Thanks.

 

Yes vss lied to the computer + then the computer gave the bad info to the tranny = early lock up

 

But the speedometer fixed itself and the trans acted up AFTER that. Do you think it could still be the VSS?

 

A new VSS is only $45 but could it be the problem?

 

VSS is the shared sensor via what the PCM sees. Possible.
Try resetting the PCM by disconnecting both positive battery cables and grounding them for an hour or so.

Are you talking 3rd or overdrive?
Do you have a converter lock-up (mystery) switch?
My converter clutch locks up at 30 mph if I have O/D locked out.
You should have O/D locked out until approx 45mph.

 

It's trying to lock up in whatever gear I'm in. I don't have a mystery switch. What do you mean by I should have od locked out until 45 mph?

 

Tranny will last longer if you leave the od off by pushing the button until you're going at higher speeds and intend to stay at higher speed.
I usually leave my od off until I'm going at least 55, normally it would engage at 47 mph. No real problem when it engages but it won't disengage until I'm down into the lower 30 mph range.
Lugs the tranny going that slow.

 

OK, I understand now. I don't think that 55 in third would work too well for me though because I have 4.10 gears and 50 is about all she'll go.

 

Oh, and by the way I put a new VSS in the transfer case and it seems to have fixed the problem. (Fingers crossed)

 

Sorry I didn't reply back earlier, but you went ahead and completed the next step by replacing the VSS. Possible the connection was coroded, but as you said, it was relatively inexpensive to replace yourself.

Another point for using the O/D lock off is the converter clutch will lock in 3rd gear. A locked clutch means a cooler running transmission when towing or or hauling or just plain city driving.

 

Thanks for the headsup. I didn't know that about third gear.