Auto trans issue, suggestions needed

[LB78]

#1317 has something going on with her transmission.

Yesterday it was pretty cold here in WI, and I let her warm up a little longer than usual before driving to our restaurant. Everything was perfect on the ride in, which is a touch less than 4 miles, most of which is at highway speeds.

However, on the ride home, everything sort of fell apart. I let her warm up until the t-stat needle twitched off the peg (this is because the rpms are all over the place until the thermostat opens - if I hit the throttle too hard she'll die). In town, there were no apparent issues. But, when I got out onto the highway, she accelerated normally up to about 60 or so and ran fine, and then all the sudden dropped out of third and into 2nd, revving high on the flats.. then tried to upshift, downshift, up, down.. a complete juddering mess between second and third. I slowed down and drove her straight home in 2nd gear, trying not to run the rpms above 3500.

I checked transmission fluid when I got home, perhaps a touch low but not egregiously so. What else should I be checking?

[jerrysony]

I had the same issue two years ago with 2607, it stucked in second gear. It turned out that fuse 13 melted.
Sometimes it's the simplest solution.

Enviado desde mi SM-G975F mediante Tapatalk

[Jonathan]

Yea, that sounds electrical to me too and not fluids related.

Check fuse 13 as mentioned and anything else that looks out of sorts behind the passenger seat.

Next up though is your shift computer governor. If that is the source of the problems, it can be from one of a few different things. Check the external cables that run over the transmission to make sure none of them are damaged or melted and shorting against metal. Look specifically at the cables that run across the transmission and near the exhaust crossover pipe. They are supposed to be zip tied above that exhaust pipe and out of the way, but if they aren't, they can get melted from the heat.

The internals of the shift computer are another possibility. Hard to see much with everything installed. Has yours ever been rebuilt with new components? The originals are prone to failing from loosened up solder joints and blown capacitors. There are instructions available for rebuilding them and you can also pay one of the vendors for a new replacement assuming your core is okay.

A way to test to see if the shift computer is the problem is (while driving) to pull fuse 13 and see if the jumpy shifting stops. No fuse in location 13 means the trans will stay in third gear. Trying to pull away from a stop in 3rd will feel like you're stuck in mud with no power, but pulling it out on the road (safely) will help tell you where the problem is. There are also ways to hook-up a small light indicator arrangement so you can see what gear the shift computer is trying to put the trans in. If you get that hooked-up and see the trans spazzing out, you know it's the computer.

Do all the fluid checks like shown in the manual. There are also other confirmations that your shift cables are adjusted correctly. That's a good thing to check, but it sounds like the shift computer to me. I would recommend against driving it very far and definitely not hard while it's doing this. Your trans will be fine long term once you get it nailed down, but you can damage it more seriously if you try and continue driving it aggressively while it's got these issues. Sounds like you already know that.

[Jonathan]

Here are some pictures.

These are my original shift computer governor. You can see where it got damaged. Looking at where this connector goes under the trans, the damaged portion wasn't heat maybe as it might have been sliced into by something or someone. Who knows. I got the car with it that way. My trans would stay in 1st gear very late, revving super high, then thunder into 2nd, and then thunder back into 1st if you slowed down a little. I put a new shift computer and cable assembly in so while it could have been just the cut cable it might have also been the electronics inside the little box there.

IMG_0378.jpgIMG_0380.jpgIMG_0381.jpgIMG_0382.jpgIMG_0383.jpgIMG_0384.jpg

And here's a couple pics of it as it is years later. Wanted to show you where some of those connections are as well as how that one cable bunch gets zip tied out of the way. See it there tied to a couple coolant pipes? And see how the crossover pipe heatshield is below it but not in contact. It's that exhaust crossover pipe heatshield to be conscious of.

These views are from underneath the car while it is up on jack stands. It's a lot harder to see any of this stuff while the car is down.

IMG_1174.jpgIMG_1565.jpg

And harder to see when those last two pics are upside down! Sorry about that, not sure why it's doing that.

[Ron]

FWIW- When fuse 13 blows, it always goes to 3rd, not 2nd.

[ritztoys]

@ LB78 Sounds like from your experiences of your cars' driving/shifting, my guess your shift computer is 'toast'. Better to rebuild/replace the shift computer before you have to purchase a new transmission.

Been there, done that! (I rebuilt my shift computer, no problems for two years)

[David T]

While it does sound like the shift computer needs to be repaired, the very first thing to do is carefully and thoroughly inspect the wiring going to it for any damage. Very common for it to get near the exhaust and get melted. If the wiring is OK the next step is to check the fluid as per the procedure in the Workshop Manual. If both of these check out either replace or repair the shift computer. If you continue driving on a bad shift computer you will damage expensive internal parts of the transmission due to the erratic shifting. If fuse # 13 was blown you would not be shifting at all, it just stays in 3rd gear, or as I call it , the limp home mode.

[DrWin]

I have a related issue I wanted to start a thread on - but this seems like a very similar problem, so I'll ask it here instead:

After changing the transmission oil (and if I remember correctly moving a cable under the car for acces) my DeLorean started to haft trouble shifting from 1st to 2nd in D or 2 on the gear selector most of the time - especially when hot. It revs very high in 1st and sometimes it feels like it disengages 1st w/o selecting another gear. If I ease off the throttle it settles in normal operation in 1st gear and if I push hard on the throttle (but not necessarily flooring it) it catches 2nd (I'm guessing? Maybe 3rd). If I instead increase throttle steadily it revs very high (3000-4000rpms) before slamming into 3rd.

I'm not sure it happens when downshifting from 3rd to 2nd. Either it goes from 3rd directly to 1st or from 3rd to 2nd fine. Sometimes when I brake really hard from 3rd gear the engine chokes and goes out. (Perhaps because it doesn't travel through 2nd?)

Strangely enough it grabs 2nd gear perfectly and with no hesitation if I'm driving in 3rd and floor it. Supposedly b/c of the kick down microswitch?
Also there is no problem shifting from 2nd back to 3rd when approaching max speed and/or easing off the floored throttle.

Anyways, I'm a little intimidated by the prospect of checking the automatic transmission for damage/errors, so any and all input would be appreciated.

[DrWin]

Here are some pictures.

These are my original shift computer governor. You can see where it got damaged. Looking at where this connector goes under the trans, the damaged portion wasn't heat maybe as it might have been sliced into by something or someone. Who knows. I got the car with it that way. My trans would stay in 1st gear very late, revving super high, then thunder into 2nd, and then thunder back into 1st if you slowed down a little. I put a new shift computer and cable assembly in so while it could have been just the cut cable it might have also been the electronics inside the little box there.

IMG_0378.jpgIMG_0380.jpgIMG_0381.jpgIMG_0382.jpgIMG_0383.jpgIMG_0384.jpg

And here's a couple pics of it as it is years later. Wanted to show you where some of those connections are as well as how that one cable bunch gets zip tied out of the way. See it there tied to a couple coolant pipes? And see how the crossover pipe heatshield is below it but not in contact. It's that exhaust crossover pipe heatshield to be conscious of.

These views are from underneath the car while it is up on jack stands. It's a lot harder to see any of this stuff while the car is down.

IMG_1174.jpgIMG_1565.jpg

And harder to see when those last two pics are upside down! Sorry about that, not sure why it's doing that.

Quick question - what's the U shaped shiny tube attached to the coolant pipe in picture 8?

[Michael]

Quick question - what's the U shaped shiny tube attached to the coolant pipe in picture 8?

Mighty auto trans cooler pipe.