lunghd

Engine/transmission cold:

• Shifts normally 1-2-3 & 4 seems 'later' than it should be.
• Does not go into lockup / "od" until approx 3 miles from house at near exact same location/distance unless it warms up for a while in driveway.
• Driving at 65 mph or more still does not go into lockup / "od" unless it's past that initial ~3 miles / operating temp period.
• Dash coolant temperature gauge is just coming up to operating temp & shows about same temp on gauge when transmission finally goes into 'lockup'/od.
• Once warm it 'usually' shifts correctly although it seems the shift points for 4 & lockup/"od" are both a bit off from before.
• Once it warms up first time for day it won't repeat until van is totally cold; ie - next morning.
• Fluid level is good - might be a bit overfilled. Hard to tell with that 5 mile long dipstick.

Background: Engine was swapped twice by a collection of genetic defectives at local garage (now out of business). They didn't exactly get their head and their a$$ mixed up with each other... but it was a near thing:

• First engine had a bad cam & it took about 3 weeks for second engine to arrive to be put in. During that 3 week time the transmission was left hanging by the crossmember w/ tailshaft up against bottom of van. Don't know if this could have damaged anything, harness maybe? Might be a red herring and be unrelated to issue.
• Second thing was that they didn't reconnect the transmission cooler properly & it blew a line off one day going down the road spewing fluid across half the county. Went through a LOT of fluid trying to leapfrog from store to store getting to auto supply. Had shifting problem prior to this but it appears to be getting 'worse'.

Is there a diagnostic flow chart up anywhere to show me what to check in what order? Or any other info/advice?

Thanks!

canucklehead

In my opinion, only a tranny shop is equipped to handle this sort of stuff. Call a couple and give them this info in your post.....
I would let them test drive it. My tranny had an intermittent issue where it was clunking in and out of lockup on the torque converter and it turned out to be the camshaft position sensor.....never would have traced that at home.

lunghd

Wanted to post a follow up to this as it took a lot of online research to find the clues to point in the right direction.

If your transmission is shifting a bit oddly primarily at cruising speeds... nothing serious, but just not 'locking up' while cruising or sometimes dropping out of lock up here are some things to check:

• The brake light switch (on pedal) also signals the transmission to 'unlock'. If this switch is bad - the transmission may unlock thinking you're stopping even without your foot on the pedal. There was no issue with my brake lights... but when I changed the switch the first tank of gas boosted the mpg from low 12's to 13.5mpg. (Didn't last as there were a few more things going on... but the change was immediate.)
• Do you have an oiled "performance air filter"... K&N etc? If so - be aware that the Mass-Air-Flow sensor (MAF) is very sensitive to the oils from these filters and will start degrading engine performance... and losing mpg. For me this loss in mpg started some time back & this is only one factor - but swapping in a new MAF along with a standard dry filter made a difference in how it's running. MPG #'s tomorrow when I fill up. (Oiled filters are ok for non-MAF vehicles... mine was factory oiled & there was no apparent over-oiling but it seems like the MAF is very sensitive to this oil.) There are a few threads online that mention the link between oiled filters and MAF sensors... and one or two that mentioned a connection to the torque converter lock up. I replaced my MAF and my transmission now locks up again on the highway! (Not perfect but a definite improvement and difference in behavior.)

Just wanted to follow up on this post as with a 7500# van the LAST thing you need is to drop from 12.5 to 11.1mpg... as mine did.
I'll post the links to those threads etc so that hopefully the next person searching won't have to dig up thirty posts from as many websites trying to figure out why his/her transmission doens't stay locked up on the highway.

These links helped me on this issue:

• 4l60e 700r4 4l80e performance gm ford transmission performabuilt
• Transmission TECH INFORMATION CODES ETC - LS1GTO.com Forums
• Diagnosing GM Converter Lock-Up Problems