I have a 86 that I have been throwing money at for a year or so .The most aggravating problem has been the auto trans .I had it serviced when I bought it .still it never sifted like I would expect I had another shop look at it and had tv cable replaced adjusted .still shifted like crap when trying to drive it normaly . Quick lo speed upshifts then bogs unless you gun it then it shudders or spins the tires . First shop was a vet shop second a auto trans shop I could have bought a trans for what I was charged so I 'm screwing with what I can on my own .
I would just stick in a rebuild in but I doubt I can raise the car high enough to pull a trans safely in the back yard
I decided to install a under car harness to stop the converter from locking . I had disconnected my speed sensor and I didn't have a speedometer but the car shifted like a normel car so I thought torque converter harness would help . When I got under to hook up the harness I found that the converter plug looks like it orginaly had three wires connected to it but one had been cut . I can't find the wire in the harness and none of the shops that worked on it mentioned that a wire was missing .Anyone know why I would have a wire missing or where it might have led. two wires are lined up on one side of the plug the cut is one the odd side and would match the odd one one th harness
The trans will work fine if you are aggressive with it or use the drive selection when off the highway . The converter harness will not work in it as it acts like a open circuit with the switch on or off . the car shifts great without the plug in the trans since the converter does not lock with it out .I think my converter locks too early causing the car to bog when you slow as the trans will act normal when I tke the converter out of the equation So I was thinking of cutting one of the two remaining wires on the plug and running a switch to them . Why the harness doesn't work I don't know .I did place a ohm meter between the prongs of the new harness plug and can see continunity on and off when the switch is thrown . I 'm assuming I 'm changing resistance with the harness and that's why it won't work in the on position ??? unless the plug isn't sitting in the trans right . I work on the ground and have a hard time getting a hand on the plug .Can barely see it above the shift linkage . It did snap onto the lock after a lot of squirming and moaning and won't pull off without lifting the lock and the prongs look ok but its just acts like a open circuit . Can the missing third wire be the culprit ????? Thanks for any suggestions Ft

 

Get a factory shop manual.

 

Are you trying to drive around town in overdrive?

 

The third wire is ground. It is not needed in your application (grounded through the metal of the trans).

The TCC is controlled by the ECM. It locks the converter at 40 MPH (it does not matter what gear you are in). My recollection is that it unlocks the TCC at 39 MPH, but I'm not 100% sure of that.

Related to Dt86's question: I never put the trans into OD unless I'm going over 50 MPH. Too much herky jerky shifting from the trans and the TCC for me.

 

Have FSM ,No comment about its usefulness in this case . i'm sure the corvette shop had one also

Thanks Cliff .that's what I needed to know . I would be chasing that wire forever thinking it was the cause of its ills . When I took it to the second shop I told them it was locking the converter too early as it will lock in at as low as 25mph when you let off throttle then if someone slows you down a bit she struggles to unlock Unless you kick down the throttle then she will release .900 bucks later it came back the same .I have 1500 in the trans still works same as it did when it came out of the barn .
.If I just keep it in drive it will shift hard especially downshifts as it slows .Trans shop said using it that way causes clutch packs to burn up . When on the freeway she works as normal in od .I had read many post here last year about keeping them in drive but my trans doesn't like it as it will slam the gears when it downshifts . Shop said they think it was modified ???/
If I disable the converter by unplugging the converter plug she shifts smoothly like it should up and down .This leads me to believe the converter is the issue . Of course this isn't fixing the trouble and its makes nuts to repair this way. i'm an engineer my stuff is supposed to be right !
Its very difficult for me to get her high enough to work on the trans .I'll have to block her up and try to get a mirror to look at the inside of the plug . hope I didn't mess up the inside of the converter plug when I attached the harness yesterday
We tried to sell it but its worth half of whats in it I sort of gave up on the car last year its been a disappointment
So I ,m trying to use it as a daily driver this summer and get some use of it .
Thought I'd give making the trans right another shot .It irritates the hell out of me to drive it this way .I know of test that can be preformed I have a download of diagnosing gm converter lockup issues but I haven't the shop to do them in .So I keep picking at it like a cavity in a tooth .ECm issue ?? who knows
Thanks again Cliff

 

Why wouldn't he? Millions of people do it every day.

 

sounds like a normal 86 tranny to me. Mine likes to go into overdrive a bit to early also, but its something you gotta live with.

 

It's real simple to run a wire to a console switch to control the lockup manually. When my car was on the street, I used the lockup as a 5th gear on the freeway. Just remeber to switch it off before coming to a stop or the car will shudder.

 

Yes that is why I bought the under car harness . i should be able to keep the converter off with it and if it worked like it should and I forget to switch it when I get off the high way it will just do what its been doing all along just a flip of the switch and converter will be off . Its a pain getting it up high enough so on my day off i will block it up again plug the cars plug back into the converter if the plug looks ok and then cut off the harness plug and splice one of the existing wires into my switch . I should have done that from the start but i thought I'd use the $40 harness and be neat about it . I drove in to work 45 mi today with the converter off and the car was actually a pleasure to drive .
Thanks again for your input gentlemen

 

But millions of people don't do it in 1986 corvettes.

 

Oooooh! Now I understand the difference. It's an 86 Corvette. Sorry.

 

Have a new chip programmed some 1986 cars locked the converter at 26 mph, have that raised to 40 mph and it will drive fine.

 

Its in the manual.

 

That says nothing about what the OP is experiencing. Your first post eluded to the fact that if you are "driving around town" you should be, by default, in the D range. Your manual clearly states "under certain driving conditions". Not the same.

 

what gear do you use, LOL

 

Actualy yes. But whatever. Have a nice day.

 

Update on what I did .
first the fsm doesn't mean much as the transmission guy said that the trans had been modified to work this way .He claimed changes to stock were made .

I placed a switch in series with the converter plug cutting the power to the converter when I don't want it to lock . When I do this the trans will go thru all the gears very smoothly both up and down .This makes the car comfortable to drive under 45 mph
If on the freeway turn it on and its like fifth gear .Or if I want to play thru turns I can leave it on and just hammer it and she will slam thru the gears .
Took it back to the trans guy this morn and we went for a ride as he didn't expect the lockout to help as much .He was surprised by the difference said maybe the original owner set it up for some kind od road racing !!
Now that I know keeping the converter unlocked makes it shift like a normal car I may look into having a prom made up to only allow it to lock over 45 like someone mentioned .I'm going to use it now as a daily driver to get some of my investment back it is fun to drive now .

 

This is the best fix.