Got towed home Saturday.
A leak developed in one of the trans cooling hoses which quickly got worse ultimately dumping all the ATF and leaving us with stranded.

I temporarily joined the hose halves with a barbed fitting and FI clamps today. No leaks. The hose will be at the store tomorrow.

This being our only working vehicle, I NEED to have the use of it.

The car no longer slips (like when low on ATF), but it will randomly downshift.
Under no load cruising in top gear, the car will suddenly downshift and rev.

I have owned a lot of cars and worked on all of them. I have never done transmission work of any kind.

Please advise. I can't afford a trans rebuild or purchase.

Thanks

__________________
Albany, NY Suburbs
'87 300D

Almost always something is wrong with the kickdown switch (under the go pedal) or the solenoid on the right rear of the transmission. Likely unrelated to your low fluid event.

__________________
James Marriott
2003 Buick Regal
1983 300D (228k, frau Auto)
1996 Suburban K2500 (192k, 6.5 turbo diesel/4WD towmaster 10,000)
www.engineeringworks.biz
1987 300SDL junker 170k
1982 300SD junker, 265k

Thanks, I feel better already.

It did a similar thing once before but soon started behaving again.
It's raining here today. Maybe it was raining the last time, I don't know.

That would make me suspicious of the solenoid.
This car has been so good that even though it's nearly 30 years old, it's a surprise when something goes wrong.

__________________
Albany, NY Suburbs
'87 300D

Check that the pressure control/bowden cable isn't sticking.

Sixto
87 300D

I had similar problems and I panicked because I didn't understand what was happening. As soon as you get an idea and find the problem things get rational and clear.
a) bowden cable sticking (I had this lately) or b) solenoid is active when it shouldn't.
trouble shooting: detach bowlen cable for a) at pump/throttle linkage and remove the kick down switch at gas pedal which activates the solenoid for b) and see if the ghost is gone.

I'll try that, thanks.

Given that it will "kick" down while cruising with my foot barely on the pedal, I doubt the switch under the pedal is the suspect but I'll check.

I'll let you know what happens.

__________________
Albany, NY Suburbs
'87 300D

There is a possibility that the kickdown solenoid is stuck also.

__________________

Gone to the dark side

- Jeff

So it's a relay and it's "frozen" closed?

Interesting.
If that were the case, then why would it get into Drive in the first place?

I'm familiar with, and fond of, relays and I would think that they would fail open.
If I'm reading the responses correctly, it looks like the kick-down is done electrically by way of a push button under the pedal energizing a relay/solenoid on the transmission.

If I don't depress the pedal far enough to depress the button, then it shouldn't have a way of down-shifting, right?

If the relay's stuck, then I would think it would stay in the lower gear from jump street.

I'm not disputing your obviously superior knowledge, I'd just like to understand how this thing works.

__________________
Albany, NY Suburbs
'87 300D

The kick-down solenoid is a hydraulic valve, can fail to return to its off position. If only partially off of its seat, it can cause irregular shifting. Cycling it by stomping on the loud-pedal can help to get it to seat properly sometimes, or fail completely, either way helping the diagnosis.

I'd probably start by dropping the pan and replacing the filter/fluid, look for lots of friction material which could be clogging the filter and starving the pump, thus altering the control pressure.

__________________

Gone to the dark side

- Jeff

Ah, thanks for that.

I read "solenoid" and saw electrickery at work.

I drove maybe 50 miles with it this morning and it's doing it regularly now.
At anything up to 55, it will just suddenly drop into 3rd and howl.

It seems that it's rare at that speed though. Much more likely at 40.
It can be a bugger to get it back up to 4th at times. "blipping" the throttle sometimes works and letting off, going to neutral, and back into drive sometimes works but sometimes I have to do it a couple of times.

As I'm no where near full throttle, I don't think the button is an issue but, as always, I could be wrong. If I disconnect the button, will that kill the solenoid or is it responding to pressure?

__________________
Albany, NY Suburbs
'87 300D

Un-plugging the button will disable it, a simple task.

It sounds like a clogged filter to me, especially if it gets worse as you drive and often works okay for the first few miles after sitting a while.

Also check the Bowden cable or kick-down cable. If it is stuck pulled out, it will cause late shifts.This cable is easiest to see if you lift the windshield-washer reservoir out.

__________________

Gone to the dark side

- Jeff

Excellent info as always.

I'll let you know what happens.

Thanks again

__________________
Albany, NY Suburbs
'87 300D

Just back from that 50 mile drive again. It was HORRIBLE!
Before I left, I unplugged the button, checked the bowden, hit it with a little oil (it moved freely in the first place) and set off.

The car drove great with only one minor hiccup in the shifting for about 20 miles.
Then, suddenly, 4th was for all intents and purposes GONE.

For a while, if I pushed it to about 50 in third, I could blip the throttle and get it to shift but that soon stopped working.

The ride back was hell. I drove most of it at 40 because that old diesel really screams at anything faster than that. I now have the trans kit so tomorrow, I'm doing the filter change and replacing both cooling lines.

I'll let you know what happens....

__________________
Albany, NY Suburbs
'87 300D

Just for kicks, go for a quick ride with the bowden cable disconnected.

Sixto
87 300D

Hmmm.

I guess I'm wondering why the bowden would act differently after 20 miles.
I'll try it though, thanks.

Although I prefer manual transmissions, I've probably owned at least a dozen automatics and never experienced anything like this. Weird.

__________________
Albany, NY Suburbs
'87 300D