Transmission just decied to down shift on my '86 560 SEL - PeachParts Mercedes-Benz Forum

nitrodog · #1 11-09-2008, 09:43 PM

First let me say I am new to the forum and if I make a few mistakes I apologize in advance and will correct them...

I just purchased a 1986 560 SEL that had been restored to almost perfect condition except for a few small or so I thought items.

I have been driving it for about a week with no problems, then today as I was driving down the freeway I noticed the rpm's jump and it felt like the car downshifted (of which it did). I pulled over checked the transmission fluid and it looked fine to me, did not smell burnt either.

I put it back in gear and slowly accelerated and it shifted fine, then it did it again, down shifted to what seemed to be second gear. Pulled over and put it in park, waited a few minutes and started to drive it shifted fine again, then did the same thing. Back down to second.

I then placed it in low, took off and shifted to second, then to drive, it would not shift into 3rd this time.

Where would I start on this model? I am mechanically inclined so I can try almost any repair as long as I know where to start.

I have fallen in love with this car and will do what it takes within reason to repair.

Any ideas?

Also where would I locate or would the CD manuals I have seen advertised be of any help with this model or are they a waste of money?

I would like to thank you n advance for your advise.

Oracle12345 · #2 11-09-2008, 10:06 PM

Send me your vin and I can send you some documents to point you in the right direction.

nitrodog · #3 11-09-2008, 10:08 PM

Do i send it in a PM on this site or by email?

Oracle12345 · #4 11-09-2008, 10:11 PM

Quote:

Originally Posted by nitrodog

Do i send it in a PM on this site or by email?

send email via site

Ill be sending them out tomorrow

nitrodog · #5 11-10-2008, 11:51 PM

Any ideas...
I do not want to go to a shop and be totally unprepared.
I would like to correct myself if i knew where to start .

Also any good ideas as to the best repair manulas out there?

86560SEL · #6 11-11-2008, 01:46 AM

Quote:

Originally Posted by nitrodog

Any ideas...
I do not want to go to a shop and be totally unprepared.
I would like to correct myself if i knew where to start .

Also any good ideas as to the best repair manulas out there?

Sorry, I probably cannot offer much help, but can try. First, how many miles are on the transmission? I almost bought a 1986 560SEL and it had transmission problems an I know of another guy with a 1989 560SEL locally that is for sale with a bad tranny (ironically, he also has a 1989 BMW 735IL with a bad transmission). I do not know if transmission issues were widespread issues on these V8 W126 cars or not, but seems to me that I have read of more problems on these than I have other MBs, at least on the 1986-91 models, but does not seem as much so on the 1981-85 V8 W126 models. I had a 1985 380SE with 275K on the original tranny and aside from a harsh shift into reverse, the transmission otherwise shifted perfectly and smoothly... no flaring, slipping, etc. Just smooth and shifted right on time - much like the transmission on my 1988 300SEL (which may have the same transmission as your 1986 560SEL? I am not sure).

I would first try to have the fluid AND filter changed (use genuine MB fluid) before I proceed with a rebuild. Also rather than a dealer or a shop that works on all cars, I would try to find a little independent shop that specializes in Mercedes, or at least German cars in general.

What about when you shift into reserve or drive? Does it engage quickly and/or does it slam into gear?

I would not think the worst yet... as it could be something simple... something as simple as a valve, solenoid, vacuum line, etc... ??

Oracle12345 · #7 11-11-2008, 02:43 PM

documents sent out. Looks your bands in your tranny need replacing

nitrodog · #8 11-11-2008, 08:34 PM

Thanks guys.

It shifts smooth but with a little lag going into revers.

I did locate a small ind shop that stated they could correct the problem for 500.00 plus 225.00 for parts, just need to decide no. My biggest problem is i love this car so I will most likely spend the $$$

david s poole · #9 11-12-2008, 09:47 AM

there is one poss problem that could explain your symptoms.within the valve body assembly there are two little filters that protect the govenor and one of them could be blocked with trash causing the tranny to downshift.these can be accessed by dropping pan and taking down valve body and then the main plate and small valve body.once you unscrew the small valve body from plate you can see the little filters and cleaqn them out.

hey_allen · #10 11-15-2008, 04:21 AM

Is there any chance it could be something as simple as a bad kickdown switch?

Oracle12345 · #11 11-15-2008, 04:00 PM

nvm

hey_allen · #12 11-16-2008, 02:40 AM

I was under the impression it was shifting, rather than slipping, but I may be misreading the OP's description.

Slipping is another whole kettle of fish, and such a load of aggravating fun to troubleshoot... I finally coughed up for the incredibly expensive ($25.00 gasp!) manual from ATSG that lets me see what all is going on in there, and was amazed just how much you can find out just by knowing what *should* be working at what point.

But as you say, no relation between slipping shifts and the kickdown switch.

rsmartin · #13 11-16-2008, 01:23 PM

i'd be sure to check the kickdown switch first. i had that happen to me in my 300SD. was driving on freeway, climbing hill. it downshifted on the way up the hill and then wouldn't shift up. next exit i got off and it wouldn't up shift at all. thankfully i was close to home and slowly drove home in first or second gear. bad kickdown switch fixed the problem.

rsmartin · #14 11-16-2008, 01:26 PM

the original post says nothing about slipping, just that it won't upshift

salinasboats · #15 11-16-2008, 05:09 PM

Hi I just rebuilt my 1991 420sel transmission because it would not change up from second gear. The problem was caused by a sheared drive pin to the governor. A small spring from a broken plastic valve in the rear valve body found its way into the secondary pump gears causing them to lockup.These gears are driven from the end of the governor hence the sheared drive pin .without the governor spinning the tranny does not know when to shift .When it first happened I drove 5 miles and the box shifted to 3rd but after that stuck in 2nd . But check the simple things first ,chsnge the oil and filter that worked on my 300e when it was reluctant to upshift . If you do rebuild the box make sure to change the plastic valves they are cheap and if you strip the valve body be very carefull take notes or better yet photos . Steve.