I just can't fix it right - PeachParts Mercedes-Benz Forum

carlover · #1 09-03-2006, 08:13 PM

My 1986 560SL will not shift out of second gear by itself, under full acceleration, unless I let off of the accelerator. The rev limiter kicks in so I have to let off, and then it shifts into third. I have adjusted the kick down linkage--no help. It doesn't matter whether I start in second, or kick down into second, it won't shift out by itself under full throttle. Otherwise it shifts fine. ( If I jump on hard from a start, it jumps down to 1st gear and shifts out fine into second, but it won't shift from second by itself until I let off the accelerator some. Any ideas ? NO, I don't normally drive the car that hard, but I want it right so when I do need to push it, it functions properly. Any suggestions will be appreciated.

Johnhef · #2 09-03-2006, 10:13 PM

good point. check the switch itself under the pedal if its stuck or swap with a known good one, its easy enough to try first.

Probabaly of no relation but the diesels have this same symptom if the boost line breaks. No power and trans don't wanna shift.

carlover · #3 09-04-2006, 09:10 AM

Thanks for the responses. No, it won't shift out of second under full throttle. There is nothing under the pedal, and if I'm going say 50mph and hit it, it down shifts into 3rd normally, so the switch seems o.k., and if I go almost to the floor without hitting the switch, it still does it. It is only in second that it won't upshift under full throttle. I hope someone else can chime in with some suggestions. Maybe there is a transmission guy around that has an answer to my delima.
I forgot to mention that the car just turned 62K miles. The previous owner was in her 70's and I doubt if she ever hit passing gear, so I don't think abuse is an issue here. All other aspects of the transmission are fine. It shifts perfectly except for this.

TX76513 · #4 09-04-2006, 09:21 AM

Carlover - did you look over Steve B's article on transmissions in the DIY articles?

carlover · #5 09-04-2006, 10:37 AM

I looked at a number of them, but didn't see anything that addressed this particular problem. I'm sure I could have missed it, or maybe I saw it and didn't know enough about it to recognize it. Which on is Steve B's article ?

C32AMG · #6 09-04-2006, 02:25 PM

If you are reaching the rev cut out point and only shifts into 3rd by backing off on the gas pedal to release the load, the K1 clutches could be slipping or a leak in the K1 accumulator, valve Body. The K1 applies for 3rd gear.

Do you have a shift into 4th gear. An oil pressure gauge would aid in diagnosing this problem. You can install the K1 spring Kit MB # 126 270 44 77 it’s about $12, it’s a quick and easy installation to do with the transmission in the car.

carlover · #7 09-05-2006, 04:12 PM

How is this spring kit installed ? I'm willing to try most anything. How do I check it with an oil pressure gauge ? I guess checking it first would be the most reasonable thing to do before attempting to install anything. What is the procedure for checking ? I am totally unfamiliar with this transmission, so any help with directions will be greatly appreciated.
Oh yes, I do have a shift into 4th normally, but I haven't tried to see if it will shift into 4th under full acceleration. I'll have to wait until the holiday traffic settles down and the speed cops are back to their normal routine before I try that. Your guidance in the checking procedure will be most helpful. I can begin there and see what happens. Thanks in advance.
Tom

carlover · #8 09-08-2006, 03:56 PM

C32AMG
I have tried to get in touch with you to find out how to use an oil pressure gauge to analize this problem, but have been unable to do so. Also, would like to know where the K-1 spring kit goes so I can try that. Can anyone else help ?

jbaj007 · #9 09-08-2006, 05:44 PM

Some reading. http://www.peachparts.com/shopforum/search.php?searchid=891994
You'll need some sort of manual. The one mentioned in one of these posts isn't perfect, but it's a start.

david s poole · #10 09-08-2006, 07:02 PM

based on all your information this problem is almost certainly not mechanical but hydraulic.i suspect that the command valve for 3rd gear is sticking in the valve body and by running up to red line and then backing off on the throttle you drop down the pressure that is holding 2nd gear engaged which allows govenor pressure to overcome it and push home the command piston in the valve body for 3rd gear.this is not a diy job you will need the help of a skilled pro unless you elect to just buy a rebuilt valve body from mercedes and put it in.all your other gears work correctly except for third [and only then under full throttle] probably caused by minor defect in piston bore in valve body aggravated by very little use and lots of sitting around.

C32AMG · #11 09-08-2006, 09:27 PM

In your case I would install the K1 kit first.

To install the K1 spring kit, the pan must be removed, inspect the pan and filter for excessive metal or clutch material, if clean; Identify the K1 as illustrated in the picture it’s on the front of the transmission. Remove the four screws on the plate, and then remove the K1 accumulator with springs. Note the sequence of the parts. Assemble the new K1 kit exactly as the one removed, then install the assembly into the valve body. 1/2hour job.

s500amg · #12 09-09-2006, 07:32 AM

Thats good to hear

carlover · #13 09-13-2006, 12:06 PM

Sorry for the delay in getting back. Thanks to all for responding and especially David S Poole and C32AMG. The comments and the picture are very helpful. I'll buy the K-1 spring kit and install it, then see what happens. Should that fail, I guess its off to the transmission shop---or just live with it. Thanks again for the help
Tom