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Auotmatic Transmission Gone Wild; Erratic shifShifting problems on a 93 LSI Conv w/ 3 Spd A/Ts
Topic Started: Jan 5 2014, 04:54 PM (761 Views)
ebry710
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I have a 1993 LSI Convertible with the 3 speed Automatic Transmission. I bought it used with 107k and now it has 117K. I am having problem understanding what to fix or test next on my automatic transmission.

What I have done:
• Change the filter and ATF – Drove 1000 miles, No Change
• Added Lucas Transmission Fix – Drove 1000 miles, No Change
• Change the filter again and added Sea Foam Transmission Tune to new ATF – Drove 1000 miles, No Change
• Changed the second gear shift solenoid and changed ATF with no additives – Drove 5000 miles No change

My thinking
I am figuring the next step is the ECU/TCU computer. The unit is marked E6.

I have this bugging voice that says, why does the transmission not know what gear it is in? Is there another input that tells the ECU what gear the console is set? Can there be a short somewhere?

Some days the transmission works flawlessly. The bands/clutches never slip. This implies to me that it is not the transmission, but the linkage, electrical inputs, controller, solenoids or a mystery device.

Observations
When I start it up, she does not perform automatically. Manually shifting the console yields:
• second gear position is first gear
• first gear position is second gear
• drive position is third gear

When she warms up (usually about 5 miles) she will lose third gear and whines out. Manually shifting the console yields:
• second gear position is first gear
• first gear position is second gear
• drive position is out

After another 5 miles or so, she does not perform automatically. Manually shifting the console yields:
• second gear position is first gear
• first gear position is second gear
• drive position is third gear

Mechanical shifting of the console is always smooth.

Sometimes I have reverse, sometimes I don’t.

Sometimes in drive, at low RPM’s, she will automatically down shift to first gear and go back to third when RPM’s go to 5000. Kind of responding like there isn’t a second gear or she thinks first gear is second gear.

On occasion works perfectly (on these occasions she is really fun to drive). In drive, she will shift automatically through all third gears. Manually shifting the console yields:
• first gear position is first gear
• second gear position is second gear
• drive position is third gear


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patrickbruce
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average teenage gearhead

Sounds like the TCM is shot... Have you considered changing ALL of the shift solenoids with known good ones?
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David95237


Pm sent check your mail.
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ebry710
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patrickbruce
Jan 5 2014, 04:59 PM
Sounds like the TCM is shot... Have you considered changing ALL of the shift solenoids with known good ones?
I will make my next purchase the TCM.

I am in California and my part number on my E6 unit is 33920-51D12. I am having a hard time finding an A-1 unit. That part number is 77-7343. I see a use one on ebay, but I think a reman. one would be best. Does anyone have a source for the TCM? Is there another part number I can use? I saw a 33920-51D13.

FMI, You call it a TCM, but the A1 Cardone part I am quoting identifies it as an ECU, it that the same part? or is there another part I should be looking for?

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ebry710
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David95237
Jan 5 2014, 05:04 PM
Pm sent check your mail.
Checked Pm, empty.
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patrickbruce
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average teenage gearhead

You should be looking for a "transmission control module"

not sure where it is in the car :dunno hopefully someone else will chime in....
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ebry710
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patrickbruce
Jan 5 2014, 07:58 PM
You should be looking for a "transmission control module"

not sure where it is in the car :dunno hopefully someone else will chime in....
I remember seeing a unit mounted vertically between the E6 (33920-51D02) unit and the steering column. Time to revisit the floor mat.
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nickb803
NickB803

I have a spare black label tcm that was pulled from a 1990 metro lsi. I cant use it because my car takes the red label one. haven't tested it but its in really good shape and the board looks brand new. $40 shipped. if you want it pm me.
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ebry710
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ebry710
Jan 5 2014, 08:10 PM
patrickbruce
Jan 5 2014, 07:58 PM
You should be looking for a "transmission control module"

not sure where it is in the car :dunno hopefully someone else will chime in....
I remember seeing a unit mounted vertically between the E6 (33920-51D02) unit and the steering column. Time to revisit the floor mat.
Found the TCM (part #85410-2450). It was the vertical unit between the ECU (E6) and the steering column. Had to remove it to see an part #.
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ebry710
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nickb803
Jan 5 2014, 08:13 PM
I have a spare black label tcm that was pulled from a 1990 metro lsi. I cant use it because my car takes the red label one. haven't tested it but its in really good shape and the board looks brand new. $40 shipped. if you want it pm me.
Thank you for the quick response, but I have to hold off on your unit. If my little research is correct the 90' is a mk2 configuration and my is the mk3 configuration. I need to do more research.
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nickb803
NickB803

yep that's true. idk if they work the same or not. if you do end up needing it just lmk.
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sphenicie


I have tested known year tcm's from 92,93,94, and 95. there was no performance difference what so ever. label color or part number made no difference. I did this by the 'swap and drive' method, in an effort to determine which were good.

if the plugs are the same on the 90, it should be fine.

when I was testing tcm's, I did not remove the one that was in the car. (it was fine). I just unplugged it and plugged the next one in. then run a ground jumper from the box to a good ground. since you are not sure if it is your problem, it may save you a little time. although it sounds like the tcm. don't toss the old one, even if it is the problem, often they are easily repairable.

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