RetroJohnny

Arising "New" Transmission Issue

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Hey everyone, long time since I've been on here, been real busy with work and what not. But I've done a lot to my Reatta, new front supension including struts and mounts, and it really is turning out into a perfect little roadster except one underlying issue. My Reatta has always had rough shifts here and there, but lately its been completely absent and shifting great. Up until today... After driving 70 + on the interstate for 20 or 30 miles, back on a smaller highway all of a sudden the transmission suddenly started freaking out. I say this because once I hit about 45-50 MPH it would be constant slipping and failure to upshift. Just terrible abrasive jolts. It would not allow me to exceed 50MPH. So we drove it straight home and I checked the fluid and it's right on par. There are some air bubbles in the fluid though (leak possibly?) but there are never puddles in the garage, and my Reatta has put 500 or so miles on it in the past month. So this is a new issue for me, and I was wondering if any of you know where I could start looking to pinpoint this issue... Hopefully not a new transmission 😰 Thanks!

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The 88-90 Reatta came with the 440T4 trans, these are very solid transmissions but they have a few long term problems which were fixed with later year 'updates'.

 

First question with this transmission: have you changed the vacuum modulator? It's often neglected and can lead to strange shifting issues. I wasn't having any issues like yours but replacing mine made major differences in the shifting. See if it's leaking fluid through the vacuum line or if it's seized.

 

Second, pull the TCC(torque converter clutch) fuse and see if anything changes. The TCC solenoid is known to fail or get gunked up over such a longer life.

 

Third, there's multiple internal issues that may have hit you that nothing but a rebuild/replacement can solve. Since it fails to go into 4th the most probable is the splines for the 4th gear hub could have sheared off as they are quite weak or a burned up 4th gear clutch as there's only one(!) friction disc for it. To test that shift it to manual 3rd and see if it drives without issue.

 

There of course can be other causes that other members may point out.

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Thank you so much, I am actually planning on looking into the TCC Solenoid, heard they aren't too hard to replace. But also everytime it rough shifted the CRT would read "Electrical Problem has Occured, Sericve Soon." So my guess it has to be elecrical if the computer is aware of it.

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Have you checked for ECM codes? On the climate screen I think you hold "Off" and "Warm" at the same time. Have your cell phone(if you have one) ready to take pictures of the codes unless you're a faster writer than me.

 

If there's no new ECM codes there's a good chance it may be a failing ignition coil and/or module. Both of mine started oozing from the heat this summer one day and for 30 minutes "Electrical Problem Has Occured" kept popping up on the CRT but no ECM codes were being set and all ECM values were okay. I changed the module and coil and the issue went away. Try undoing the screws that hold the ignition coil to the module and see if there's goop in between them. If there's a lot of goop it's time to replace them.

 

As for the TCC, you can try disconnecting the 4 pin connector from the trans temporarily and going for a short drive under 50mph. If the issues go away it's almost certainly a messed up TCC solenoid. Remember to reconnect the cable!

 

I've seen people on this forum correct their TCC solenoid issue with additives like Seafoam transmission cleaner but I have never tried it and generally discourage adding anything but ATF to your trans unless it's a last resort. If you determine it's the solenoid you can look into the seafoam cleaner at your own risk.

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Also, trying cleaning that 4 pin connector on the trans too. On mine I had an error code for 2nd gear circuit fault since day one and after cleaning the contacts it went away.

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Yes, I have checked the codes, the only code I found was E039, which the Reatta Service Manual reads "TCC Circuit" , So hey, maybe it is that simple of a fix. And I couldn't be the ignition coil or ICM, those were replaced not two months ago becuase I had exactly your problem, sticky gooey stuff coming out of it. But exactly your thought, the TCC is what the computer thinks it is, so that is going to be my first fix! I checked and they are about twenty dollars on RockAuto.

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Good on both counts then. Check the fuse and clean the connector first. I used a small file to gently scrape the tarnish off the pins, that alone got my TCC working. You may wish to gently bend the pins on the connector to increase their contact when plugged in too. Changing the TCC solenoid won't be fun. Pick up a side pan gasket as well, gotta assume the old one isn't coming apart in one piece. Then you gotta figure out how to get the new one on with the axle in the way. 🤧

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See if you can find DeoxIT in  your area. It works miracles on cleaning low voltage connections like on the transmission. I use the liquid in a small tube. I have to order it from Amazon. I've not found it around here. I guess the spray would be good too.

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Any time a GM automagic acts up I drop in a can of Seafoam Transtune and drive a bit. valves tend to get sticky over time and this cleans them out. Mostly.

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