Lizard928

Only use Redline 75W90NS in your gearbox!!!!

For the windows, check the fuses and relays first.

karl ruiter

I have kind of come to think that you just have to learn to live with a notchy/noisy OB transmission. The cost of a rebuild is more than the value of the car and, even with the best quality rebuild it is a temporary fix. Redline is said to help, but I did not notice a big improvement.
On the windows, I start by pulling the door panels and hooking my battery charger directly up to the window motors. That will tell you if it is motors or switches. The motors are pretty easy to remove and repair. It is just a matter of putting in fresh grease and cleaning the commutators. If it is the switches don't mess with then. Just replace.

Maleficio

Not meaning to be argumentative, Lizard, but I wonder about the urgency of your statement because Redline gear oil did not exist when his car was delivered from the factory. To say that only one oil can work in an old gearbox is kind of a stretch to me.

Lizard928

Its not that only 1 oil will work.
Its that only one oil will work extremely well.
The 75W90 NS has a Non Slip modifier. So it lubricates, but has some special additives to help the syncro rings grab and work thus reducing slippage, and increasing their life.

Maleficio

Jadz928

You are hardcore, man!
Alot if work to pull the panels to find out.
You can test for switched power at the harness connector, near where it enters the door. This will let you know if you need to remove the door panel, or not.

Landseer

Terminals 1 & 2 IIRC

dprantl

I don't understand why it's a lot of work to pull the door panels? It takes like 10 minutes and just some normal tools.

Dan
'91 928GT S/C 475hp/460lb.ft

Jadz928

I'm not saying it's difficult, just not necessary to diagnose if you have a failing window motor.

You're talking 30 minutes total, where you can put an MM on the harness at pin 1&2 in less than 5 minutes. That is all.

OldGuy

Ok what Oil am I supposed to use for my tranny to make the notchyness go away?

And I am sure its the motors/regulators. The windows immediately react to the switches. The passenger went all the way down and will come up with switch activity. I dont see how it can be the switches. SOMETHING happens everytime I push a switch.

Landseer

There are cylindrical plastic guides on the window apparatus that wear-out. A sign is if the window is binding. A few zip ties through it can be a patch.

The motors and the gear reducers themselves get gunked-up and so do the terminals at the motors. Jadz928 did a clean / refurb on some and there is Wally commentary along with it that is helpful. The gunk mechanically and perhaps electrically (resistance) will slow the actuation.

On the door panel deal, if you remove, best to have a big clear shower curtain on standby. You can cut it and install it with contact cement as a vapor barrier between door and panel because you will damage the original polyethylene in the process of accessing the motors. Mr. Merlin always reminds us about this because other wise the panels can get wet as the door/window system drains.

There is a big 18pin white connector on each side of the car, tucked up near the L-jet unit on the right and near the hood release on the left. That is where you can break-into the door wires for speakers, lights, mirror, lock motor and winder. IIRC the winder terminals are 1 & 2 and reverse polarity via switch for direction. I think this is a unit without a separate ground, so two wires instead of three. Check to be certain. The wiring diagrams are really useful if you take time to learn how to read them. Brilliant actually, even the oft-maligned 84 diagrams.


Just about everything on the 928 can be disassembled in some specific sequence and repaired. Makes it a DIY guy dream, especially the sequence part. If you like working tavern puzzles, grab tools and dive in.

If you want, you can cheat and look it up in WSM or more practically, here in the forum and get step by step's.



Car is nearly 30. Stuff will need attention on a regular basis. The fact you can compare it to any current Porsche is amazing, btw.

Lizard gave the bestest fluid recom. Notchy is normal, even in later boxes. They don't seem to be made for speed-shifting at all. Remember they are GT cruisers.

A 2 - 3 shift for me is really a 2 - N - 3 shift. My boxes are old and worn. Am running Mobil 1 LS. Driving a half mile in first to warm the box everyday (slowly). Am experimenting with an extra quart of fluid in one of the boxes and it seems better, but not much.

Jadz928

Interesting, and true.
I have a puzzle over here you can work on...