[W126 Coupe] High RPM Shifting Problem

[Vance Rowley]

Hi Malcolm,

  I can't tell from your diagram if the link I referred to is #22, It could 
be. If you want I could take a photo of the one to be sure. The problem you 
are experiencing is a different problem by the sounds of it to the one Barry 
has. Just by coincidence, I had exactly the same problem 4 or 5 years ago 
that you have with my 1991 Euro 560 SEC. At the time I was In Greece, so 
luckily the labour costs were reasonable at the local MB service centre. 
Like yours, It would shift fine except from 1st to 2nd and everything else 
was OK. You are exactly correct that the pressures should force the tranny 
to upshift to 2nd, but at the time my pressures were tested and fine. They 
stripped my tranny, cleaned, rebuilt with new filter fluid and so on, but 
the problem was still there. I eventually gave up as it was quite driveable 
as the only problem was from 1st to 2nd. Then one day I dumped some tranny 
reconditioner fluid into the tranny that I had lying around for a long time. 
I forgot the name of it and didn't think I could do any further harm. Then 
suddenly after driving for about a week (to and from work) due to traffic 
conditions, I was forced to floor it and it suddenly started working 
perfectly and has done to this day. It was after this, that I learned about 
the link I mentioned as all of my shift points were now all out at WOT. This 
was due to the MB centre adjusting this link so I would have earlier shifts. 
I then decided to re-adjust it myself and it only took me 4 or 5 attempts to 
get it bang on. The problem Barry mentions sounds like the link as he has 
the same problem through all gears and not just from 1st to 2nd. I would 
advise Barry to try this first as it is simple to do yourself and costs 
nothing except a little time. if that fails, then yes, then I would have the 
pressures tested and fluid and filter changed and so on.

Cheers,

Vance.

----- Original Message ----- 
From: <malcolm369 at comcast.net>
To: "Vance Rowley" <vance.rowley at tiscali.co.uk>; "Mercedes Coupes Mailing 
Lists" <mbcoupes at mbcoupes.com>
Sent: Friday, April 28, 2006 7:32 AM
Subject: Re: [W126 Coupe] High RPM Shifting Problem


> Hi guys,
>
> Here is a drawing of the throttle from the MB CDs. I believe the link you 
> refer to is 22, correct? if so there is no vacuum there, at least that I 
> know of.. That said, I'm not convinced the linkage is the answer to this 
> one, and is a good place to start.......
>
> My transmission currently is refusing to upshift at WOT only when in 1st 
> gear. Hits the rev limiter. It is normal shifting at WOT (and otherwise) 
> in every way in all other (2, 3, 4th) forward gears. The three W126 gurus 
> at my dealer concur there is a mechanical problem with the governor that 
> gets into the valve body that causes the problem. I'm told this was a 
> relatively common problem (back when) when experiencing a transmission 
> anomaly. In short, they've seen it before.. more than a few times over the 
> years.
>
> At WOT hydraulic pressures should force the transmission to upshift into 
> 2nd which isn't happenning.
>
> The replacement parts (Germany) came in yesterday. Appointment made for 
> May the 4th. I'll keep you posted.
>
> Cheers,  Malcolm
>
> -------------- Original message ----------------------
> From: "Vance Rowley" <vance.rowley at tiscali.co.uk>
>> High RPM Shifting ProblemHi Barry,
>>
>>  It sounds like you have a very simple problem. In fact it is just 
>> usually an
>> adjustment you need to make. I can't remember the correct name for it, I 
>> think
>> it is called the throttle/vacuum link. But basically there is a metal 
>> link
>> behind the air filter (between the air filter and the firewall) this 
>> metal link
>> is in two parts bolted together (I think with a 10mm bolt) which can be
>> lengthened or shortened by loosening the bolt and sliding them apart (or
>> together) so it becomes longer or shorter. The length of this link will 
>> depend
>> on where your shift points will be. this link is fastened at each end 
>> with a
>> ball joint as such and can be removed completely (just clips off and on) 
>> to
>> adjust the length easily, then replace. It's been many years, so I can't
>> remember if it is a shorter or longer link that will lower your shift 
>> points,
>> but you can easily experiment as it is very easy to get to and adjust. 
>> You
>> ideally will need a nice clear straight road for a test as once you get 
>> close to
>> the adjustment to get it spot on, you will need to floor it from a 
>> standing
>> start and make sure your shift points are spot on the red line (or just 
>> before
>> in your case if your tachometer is slightly out of calibration) or better 
>> still,
>> go off your marks on your Speedo.
>> Hope this helps.
>>
>> Cheers,
>> Vance.
>>
>> P.S. Been many years since I was in your part of the world. Are there 
>> still many
>> good places around Gas Town. Not forgetting the Indian Restaurants.
>>   ----- Original Message ----- 
>>   From: Barry Sharp
>>   To: mbcoupes at mbcoupes.com
>>   Sent: Friday, April 28, 2006 12:52 AM
>>   Subject: [W126 Coupe] High RPM Shifting Problem
>>
>>
>>   Greetings from the wet coast (Vancouver, BC).  I have a 1989 560SEC 
>> Euro model
>> with about 106,000 km.
>>
>>   I've noticed a problem with the transmission not shifting up at maximum 
>> rpm.
>> Last weekend, when passing another vehicle doing about 90 kph, I put the 
>> gas
>> pedal to the floor and the transmission shifted into second.  As I passed 
>> the
>> other car, I got up to around 120 kph and the car started jerking.  I 
>> backed off
>> the gas and the transmission shifted into third.  I figured that it was a 
>> rev
>> limiter kicking in.  I was quite concerned, so I thought I'd check it 
>> out.  It
>> didn't matter whether the transmission was in Economy or Standard mode, 
>> it would
>> not shift into third with full throttle at 6000 rpm.  The rev limiter 
>> kicked in
>> and the engine started missing very badly.
>>
>>   I also tried a full throttle shift from third to fourth.  Same problem. 
>> At
>> about 200 kph with 6000 rpm and full throttle, it would not shift into 
>> top and
>> the limiter kicked in.  Having the car shaking you about at 200 kph is 
>> quite
>> disconcerting.  It felt like the drive train was shaking itself to 
>> pieces.
>>
>>   Other than the high rpm shifting issues, the engine and transmission 
>> seem to
>> work perfectly.  Any thoughts as to what the problem is and should I have 
>> it
>> seen to?
>>
>>   Thanks in advance for your help.
>>
>>   Cheers...Barry
>>
>>   1989 560SEC 106,000 km
>>
>>
>>
>> ------------------------------------------------------------------------------
>>
>>
>>   The MB Coupes Website!
>>   W126 SEC Mailing List
>>   Postings remain property of MB Coupes, L.L.C.
>
>
>
>