no overdrive on the 88

[marquis_82_withneons]

planning on taking a poke at the OD issue soon. checking the valve body and gonna runs a trans additive with a fluid and filter change to see if it helps.

any suggestions or am i wasting my time?

[miamibob]

I'd do the cheaper/easier stuff first as it shouldn't further damage anything.

[pantera77]

Honestly, IMO your wasting your time. Tranny fluid ain't cheap either. It's probably a cooked OD band, my 88' as well has a wasted OD band. Drive it as is and just leave it in D for the time being.

[marquis_82_withneons]

i agree with you pantera, i feel i am also. but im trying to stay optimistic because the i need that OD. its killing my mileage bad. and taching 3k everywhere i drive isnt the best for the motor. my question is how can the OD go out with such low(er) miles? and the car was never abused. which is obvious. everything on the car is original and i have no leaks no abnormal wear, nothing, just warped rotors and rusty exhaust. even the bodys straight. rusty but straight.

side note. a good 75% of is life was spent on dirt roads, would that play into anything?

[marquis_82_withneons]

id also like to say that im not doubting any of you guys. i value all your help too much to be a dick and make everyone hate me. im trying to understand all of it and somewhat learn something of these issues.

[marquis_82_withneons]

finally getting to the OD today... fluid change and additive going in with a filter kit. hoping to get back the OD. am i correct with 12qts of mercon v? or can i run ATF or DEX/MERC (III)?

[DerekTheGreat]

[QUOTE=gadget73;733520]Usually when the OD band goes, it does a 3-neutral shift, not a no-upshift. QUOTE]

I'm no expert but when Ashley bought her '89 TC we bought it with a smoked trans. All I knew at the time was that if that little white plastic grommit fell off then OD goes and then the rest of the trans goes with it. First thing I did was check under the hood during the test run and sure enough the TV cable was just hanging there missing the white grommit. Bought it any way and replaced the grommit with the updated brass one and then drove it to see if it had OD. Car started in 2nd, shifted to 3rd fine but when it shifted into 4th it's just like gadget said, it's like it shifted into neutral. No drama, just free rev. Placing the shifter into first made the car not want to move. Turns out there was all kinds of crap in the valve body, clutches were smoked and the OD band was busted. I didn't see an answer on whether or not your car shifts at all after 3rd but from the sounds of it it's just holding third. I'm no expert but I'd try looking into the valve body since you're going to have the pan of anyway.

[marquis_82_withneons]

thats the difference with mine though. it doesnt shift into nuetral. its just doesnt leave 3rd. all shift points are perfect, no shuddering, no slipping, just doesnt go into OD.

the bushing was also perfeectly intact. it is however replaced with a brass one now.

for the record i agree with you. im thinking clean the valve body

[sly]

do not run type F in an AOD. merc III is ok, V is better. Also, check your shifter alignment. Mine was half out and would lock in D and not shift to OD but holding the shifter up a little allowed OD to engage.

[gadget73]

I half wonder if someone changed the overdrive servo and didn't get the pin back in. Either that, or maybe the OD servo seal is leaking and its not going in. There are a couple of valves in the body that might possibly stick and cause a no 3-4 shift too. I could dig out the drivetrain manual and look through it if you're really keen on dicking with it but deep down I don't think servicing it alone will fix it, but I also don't quite think you need a full rebuild. Might be absolutely wrong on that, but thats just my feeling. If you drop the pan and its full of clutch material, that will tell a different story though.


Dex/Merc is fine, Mercon V is fine. Mercon V is more for the torque converter clutch design that the electronic transmission used. DOn't rightly know if there is much, if any, performance gains to using it in an AOD. Do not use Type F though.