[W126 Coupe] High RPM Shifting Problem

[malcolm369 at comcast.net]

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 
> 
> 
> 
> ------------------------------------------------------------------------------
> 
> 
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