Help! my 4+3 shifts slow in my 88 coupe. You will see the dash OD light come on, and the actual shift comes about 2 seconds later, almost to the point where it wants to downshift the OD because it thinks you are jumping on it. Back off on the R's just a little, and you get a nice shift. It is really bad when I come out easy and let it shift into OD in second gear, because of the delay time the car starts to think I'm racing and cancels the shift, then I go for third and get a two for one (third and OD). ALSO, when I bank a turn on an offramp, or turn the corner at the end of my street which is a little bit of a downhill turn, it wants to downshift the overdrive, making the RPM's jump up and making the OD seem like it's slipping. It doesn't do it on the turns if I maintain a constant motor RPM, kind of hard to explain... but by this time I'm holding up traffic. The trans was rebuilt about 25-30K ago and worked fine up until recently. I had the filter and fluid changed a few months back, but it didn't solve the problem. My mechanic said the fluid wasn't burnt or anything, and that he took about the right amount of fluid out, quart and a half I think, (unless he was lying to me and never even touched it... hmmm.... ). When it shifts, it shifts firm, and has that distinct "clunk" when I come to a dead stop, seeming to indicate that the OD is shifting good. Also, it has engine braking in OD, so I don't think I have burnt clutches.

Any thoughts????

 

Mooncricket,
There was an earlier post - Wednesday or Thursday where the OD shifted erratic and he replaced the OD relay.

I have a slight problem with mine where OD does not work in 3rd or 4th unless it is active in 2nd. I am going to try replacing the relay - about $15.

Good Luck,

 

I would have to agree it does sound like a relay especialy if you get a firm shift when it does shift.

David Fulcher

 

I'm going to definitely check out the relay. For $15 bucks, you couldn't go wrong giving it a shot.

4+3 is so much more fun than my 92' LT1/auto... I'd love to get it straitened out...

Thanks

 

So I went out and bought two new relays for $13 bucks a piece, and switched out every relay I could and it shifts the same. Here are the relays I found and tested with a new one:

1. One between Vacuum Booster and windsheild wiper motor, pretty sure to be the fuel pump...
2. Two on the rear of the driver-side fender well, HAVE NO IDEA WHAT THEY ARE FOR...
3. One on the Fan shroud, leading right to the fan motor... guessing it's the fan motor, duh.
4. Two behind the battery on the firewall, one of which I am PRETTY SURE IS THE OD RELAY...

Which one should it be, and did I miss the OD relay somewhere? I think something else might be up...

 

You have email - picture of relay locations from service manual.

Look for #16 - located behind fuel pump relay. Be careful - all the relays are NOT the same part #.

 

Got your email, coundn't open the attachment on my cheesy computer. I came back to the forum and saw that it was the service manual diagram that you sent. My 88' service manual says the same thing, but it aint' there, thus leading to my confusion...