Only Shifts at high Revs *Help!*

[MPDano]

Guys, need your input on my 83 S.

My S has always had a pretty good leak in the tranny. I just top it off every 2-3 weeks. Been like this for years. A couple days ago, I punched it on a freeway on ramp. Now when I start off from a stop, it goes to about 4k before shifting. Also, when I usually top off the fluid, it's normally very very low. This time the reservoir was full and I don't get the leak I normally see when I am under that car.

Is some pump not working? Something disconnected? Something blocking a valve of sorts? Maybe a fresh fill and new filter might dislodge? I dunno, any thoughts?

She is down for the count until I can sort this out. This was my DD.

[dewolf]

Bowden cable? Vacuum modulator?

[Crumpler]

modulator would affect quality of shift only, I think.
It sounds like a higher control pressure now because of the upshift at the higher RPM?
Selector lever moving the spool valve for flow?
Sorry Leo, I know that may not be a lot of help.
Man, the automatic tranny is so complex, it's always been like a Gordian Knot to me.

[harborman]

With a trans leaking all the time and having to top off the fluid, you may have caused some damage when it was low on fluid when you punched it. It may have some internal blockage, worn bands, etc. Can you manually do the shifting with the shift lever? Maybe time to drop the pan and see if any metal deposits in it. Remove the filter and have a look.

[MPDano]

Yeah, the auto is a complex beast. Just wanted some input prior to dropping the pan. I have a new filter and a a full set of o-rings that I was going to replace when I pull the tranny at some point. I will at a minimum replace those o-rings on the side of the tranny that I can get to without dropping the tranny where I also believe is where the leak was at when I replace the filter.

Keep the input coming!

[harborman]

It is not too hard to drop the pan and filter. I did mine last year. If you see a lot of junk in the pan then you will know of possible serious problem. On mine, it was so clean you could eat off of it. Only problem I encountered was removing the filter. Screws were in real tight. I took a hand impact driver to them and fortunately all came out fine. Do not over tighten pan gasket when reinstalling. I also drained the torc converter. You need to position drain plug on converter to correct position by manually turning engine over so plug is at bottom for access.

[MPDano]

Originally Posted by harborman

It is not too hard to drop the pan and filter. I did mine last year. If you see a lot of junk in the pan then you will know of possible serious problem. On mine, it was so clean you could eat off of it. Only problem I encountered was removing the filter. Screws were in real tight. I took a hand impact driver to them and fortunately all came out fine. Do not over tighten pan gasket when reinstalling. I also drained the torc converter. You need to position drain plug on converter to correct position by manually turning engine over so plug is at bottom for access.

Yes, I have gone through all this when I first bought the S

[Fixer]

Hey Leo, here you go;

High RPM Shifts:
Check pressure control cable engagement, condition and
adjustment.

Check for stuck kickdown solenoid or for constant voltage
to solenoid caused by a defective fuel pump relay or sticking kickdown
switch. (My guess)

Check governor pressure. If regulator pressure is too low,
replace centrifugal governor.

Ensure control pressure regulating valve
is operable.

[lfausty]

lucas trans repair possible save?

fluid
thickened fluid then adding when you see low then gets warm unthickens now overfull. overfull creates foamy . foam no liquid creates heat/no friction damage. maybe can drain qt/see foamy/replace with more?

low before adding burnt no friction properties ,heat/damage. low adding to burnt prob no better not enough good juice.

hopefully as no one knows better than u , with an eagle eye/ear, that a miniscule mishap the second it happens, luckout and save it.

[MPDano]

Thanks guys for those suggestions. I think I will try and drop the pan this weekend. My big worry is that the internal pump is bad as the reservoir was full when I went under last, it normally isn't full but real low. Plus I normally get a very slow drip and that disappeared.

Any last suggestions that could point directly to those symptoms I just described?

[Mrmerlin]

check the kickdown solenoid switch at the top of the pedal it may be stuck closed,
also check for click when the pedal is pressed with the key on and engine off.


Fix the leaks no good comes to the trans from running low fluid

[MPDano]

Originally Posted by Mrmerlin

check the kickdown solenoid switch at the top of the pedal it may be stuck closed,
also check for click when the pedal is pressed with the key on and engine off.


Fix the leaks no good comes to the trans from running low fluid

Will do Merlin. Remember I also have a kicdown bypass switch next to my e-brake. I'll see if I can hear a click when activating it.

Yeah, was my intensions to try and replace any o-ring I can get to with the pan off and tranny still in. I bought a full set up o-rings for both this tranny and Euro tranny a couple years ago.

[Mrmerlin]

use DC111 on the new O rings

[MPDano]

Couldn't do much on the S, but I did verify the kickdown solenoid is clicking.

[Hold On]

Small section of rubber vacuum hose located forward in trans tunnel connects the two metal lines. One metal line going forward from trans and other from front of intake plenum,around engine and down trans tunnel.
If thissmall rubber line comes off or cracks, it provides no vacuum for modulator, which causes trans to only shift up because of excess pressure.
Its difficult to see this small section in trans tunnel. My 83S had same problem and I traced it to this vac line. New rubber hose section and it was good as new.

[MPDano]

Fixed my hard shift and part of my leak issues. The hard shift was the Central Governor on the tranny that also connects the infamous deteriorating two small hoses. You can see where I put the arrow is where my governor was previously repaired using some epoxy. It didn't hold anymore vacuum so it decided not to work or barely work. I removed the one off my Euro Tranny and it now shifts. One of my large leaks was the o-ring on this Central Governor. I didn't have a replacement but the one off the Euro Tranny which was very pliable. I just cleaned it and added some dialectic grease.

I still have a very small leak on the opposite side of the tranny (pass), but hose can wait as I can actually drive my 928 now.

Shifting kinda lags since it was set up for the Euro gearing so I'll also have to adjust this later. I'm good with it for now.

[Landseer]

That's the vac modulator valve. Glad you got it fixed!

Governer is a spining whirring thing inside one of the covers.

[MPDano]

Originally Posted by Landseer

That's the vac modulator valve. Glad you got it fixed!

Governer is a spining whirring thing inside one of the covers.

Thanks Landseer.

Looks like they are pretty inexpensive too. I see brand new ones at around $29

Also, looks like they updated it as well.

[MPDano]

Did some googling and found that by adjusting the vacuum modulator "clockwise" increases pressure, in turn gives a harder shirt. "counter-clock" lower pressure softer shift. Too low of pressure will give a flare/slip shift. Also, make sure the rubber cap over the adjusting pin is not cracked, best to get a new one as this causes vacuum lose.

[MPDano]

Adjusted the modulator 3 clicks and she was flaring a lot worse. I went back 6 clicks and she shifts a whole lot better. Will report tomorrow as I will drive her to work again.

Here are some pics of where to adjust with the cap on and off