Lockup switch vs Overdrive.. I'm stumped!

[Bobcat698]

I have two trucks that have the same problem.

One is a 97 Auto with Goerend Valve body.
The other is a 98 Auto with Goerend Valve body, both 12 valves.

They both have aftermarket, GOOD converters in them. Both have VBA's installed and also have noise isolators as well.

Recently, the 98 starting giving me issues with locking up in overdrive.. It wouldn't lock up, but if you let out of the throttle, then got back in it, it would generally lock up.
I put a lock-up switch in it to see if I could force lockup sooner.
The valve body is set up to lock up in 2nd-4th gear.

If you hit the lockup switch in overdrive, with the converter unlocked, it does not immediately lock up. Instead, you have to let out of the throttle, let the RPM's drop to 1500RPM or so, then re-apply the throttle. The converter will then lock and stay locked until you hit the switch again.

The 97 does the same thing as well, though it usually does lock up in overdrive, the 98 is more likely NOT to lock up on its own.

The main difference between the trucks is the 97 has 3.54s and WILL lock up if you accelerate heavily with the converter unlocked in overdrive. The 98 has 4.10s and will not lock up if you accelerate heavily, unless you let out of the throttle and get back in it with the switch to the locked position.

Anyone have any ideas? This is driving me nuts!

 

[BgBlDodge]

Does it do it only when cold? Mine has done something similar for the last 4-5 years but only when the fluid is below 160*.

 

[Bponci]

Put the rear of the truck up on stands and run it into o/d. Either put a pressure gauge in the cooler line or pinch it with your fingers and force a lockup. The pressure in the line should increase or you should feel a pulse in it. This will tell you if the solinoid is doing its job by dumping the converter and locking it up.

 

[Bobcat698]

I will try that asap, thanks for the advise!

Tyler, either truck does it warm or cold, though the trans temp is always below 160 this time of year.

 

[CSnyder]

Are the kickdown cables adjusted correct? Make sure they start moving as soon as the throttle is depressed or you will have weak line pressure. Also double check fluid levels and read it off the lowest side of the dipstick when up to temp in nuetral.

 

[Bobcat698]

Are the kickdown cables adjusted correct? Make sure they start moving as soon as the throttle is depressed or you will have weak line pressure. Also double check fluid levels and read it off the lowest side of the dipstick when up to temp in nuetral.

Yes both have correctly adjusted TV cables, and the fluid level is good in both.
Thanks

 

[CSnyder]

Got any spare TPS's around to swap in. We had a similar issue with lock-up 2 days ago and swapping the TPS fixed the problem.