why would........

[NOTSOFAST]

this past weekend I decided to take out GN #2 for a ride and stretch her legs. but at between 20mph & 45mph, the tc jumps in & out of lock up. after changing gears tranny will not stay locked up at cruising speeds. so it bucks and speedo acts up bouncing everywhere & it makes GN feel as if it is missing. but If I get on it at higher speeds, the speedo settles down. and GN runs smooth all the way up to 25lbs, or cruise at 80mph.

 

[longball]

possibly failing lockup solenoid

 

[Dusty Bradford]

The TCC is usually programmed to lock at 45mph. If your crusing at speeds right around this point it can lock and unlock depending on speed and other ecm parameters. I always put the shifter in D when cruising at those speeds. It seems to help keep it from locking and unlocking so often. You also have to run above or below the lock-up point or else the ecm will continue locking and unlocking the converter.

 

[Steve V]

If your speedo is bouncy it could mess up the vss signal....if it is bouncy because TC in and out then disregard.

 

[mikestertwo]

If your speedo is bouncy it could mess up the vss signal....if it is bouncy because TC in and out then disregard.

Disconnect the plug on the side of the trans to dissable the lockup and verify the speedo isn't bouncy. As mentioned above if the speedo is unstable it will affect the lockup.

 

[NOTSOFAST]

Disconnect the plug on the side of the trans to dissable the lockup and verify the speedo isn't bouncy. As mentioned above if the speedo is unstable it will affect the lockup.

what plug are you talking about?

 

[mikestertwo]

There is a connector on the left side of the trans near the shift linkage that feeds the lockup solenoid and the 3rd and 4th gear status switches. Disconnect it and take it for a drive.