Over a relatively short period of time my E300TD Turbodiesel's autobox started giving me very rough gearchanges on all upchanges, feeling worse on the 3rd/4th change. It felt so bad that I worried about my diff being ripped out and the prop-shaft bouncing down the road following it.
First thing to do was drop the oil, change the filter and refill with fresh and cross the fingers that all the jerkiness flowed out with the old (and surprisingly clean) oil.
Quick test drive. No change. Bugger!
Now the trouble with auto boxes, especially of this vintage, is they're tough, reliable and aren't fussy about oil changes! Which means that you don't get to tinker with them much. Mr Haynes in his manual shies away from even touching anything oily in them!
So the thin section on auto boxes in the Haynes manual is only good for bog paper.
So I go and seek a professional autobox bloke's opinion who's fixed a couple of Merc boxes of people I know.
After a test drive he says the clutches are worn and to do an overhaul think of around £1200 give or take a ton.
It sounds plausible. When the clutch bands wear out maybe they go downhill fast? I don't know.
Then I post on here looking for options, ideas, suggestions and looking for a spare box.
Here's the rare sight of a turbodiesel under the bonnet of a W124. I think it's a great looking engine. No plastic covers and all quality components. (Note the optional heated washer bottle)
So starts the steep learning curve with getting to grips with auto transmissions and, more importantly, the vacuum systems that control the gearchanges. This lead to doing a little swapping around to test certain components.
Picture 1
This is the standard set up with the supply of vacuum on the right and the outgoing vacuum to the gearbox on the left with the green inline filter.
Picture 2
Now the unit is bypassed with vacuum coming straight from the pump.
Result. Smooth, soft gear changes.
So either the control unit is failing or the modulator valve on the gearbox needs more vacuum than the control unit can provide.
After feeling all smug that I've logically got to the bottom of the problem I look at the control valve bolted on to the Injector pump. It's an impressive aluminium casting that looks as though if contains 10,000 tiny springs assembled by a Swiss watchmaker, at great expense, in a clean room, in some laboratory, in Zurich and will explode when the cover comes off!
If this was a French car it'd look like a bit of Tupperware and be velcro'd on.
But hang on, it's only 3 pneumatic tubes and two 10m bolts holding it on, what have I got to lose.
I marked up its position with a scribe and unbolted it.
Here's the control valve in pieces off of the IP. Looks in good condition and only 1 spring!
Looking more closely though the inlet vacuum brass jet is blocked with a bit of gunge.
After a bit of careful cleaning the jet is remounted in the valve housing and reassembled.
After remounting back on the Injector pump, a bit of adjustment, and all is well again.
Seeing as some specialist test driving the car and wanting £1200 to overhaul the box and I was contemplating buying and fitting a secondhand gearbox (sorry Ian) I think this is a result and makes me appreciate MB engineering even more.
First thing to do was drop the oil, change the filter and refill with fresh and cross the fingers that all the jerkiness flowed out with the old (and surprisingly clean) oil.
Quick test drive. No change. Bugger!
Now the trouble with auto boxes, especially of this vintage, is they're tough, reliable and aren't fussy about oil changes! Which means that you don't get to tinker with them much. Mr Haynes in his manual shies away from even touching anything oily in them!
So the thin section on auto boxes in the Haynes manual is only good for bog paper.
So I go and seek a professional autobox bloke's opinion who's fixed a couple of Merc boxes of people I know.
After a test drive he says the clutches are worn and to do an overhaul think of around £1200 give or take a ton.
It sounds plausible. When the clutch bands wear out maybe they go downhill fast? I don't know.
Then I post on here looking for options, ideas, suggestions and looking for a spare box.
Here's the rare sight of a turbodiesel under the bonnet of a W124. I think it's a great looking engine. No plastic covers and all quality components. (Note the optional heated washer bottle)
So starts the steep learning curve with getting to grips with auto transmissions and, more importantly, the vacuum systems that control the gearchanges. This lead to doing a little swapping around to test certain components.
Picture 1
This is the standard set up with the supply of vacuum on the right and the outgoing vacuum to the gearbox on the left with the green inline filter.
Picture 2
Now the unit is bypassed with vacuum coming straight from the pump.
Result. Smooth, soft gear changes.
So either the control unit is failing or the modulator valve on the gearbox needs more vacuum than the control unit can provide.
After feeling all smug that I've logically got to the bottom of the problem I look at the control valve bolted on to the Injector pump. It's an impressive aluminium casting that looks as though if contains 10,000 tiny springs assembled by a Swiss watchmaker, at great expense, in a clean room, in some laboratory, in Zurich and will explode when the cover comes off!
If this was a French car it'd look like a bit of Tupperware and be velcro'd on.
But hang on, it's only 3 pneumatic tubes and two 10m bolts holding it on, what have I got to lose.
I marked up its position with a scribe and unbolted it.
Here's the control valve in pieces off of the IP. Looks in good condition and only 1 spring!
Looking more closely though the inlet vacuum brass jet is blocked with a bit of gunge.
After a bit of careful cleaning the jet is remounted in the valve housing and reassembled.
After remounting back on the Injector pump, a bit of adjustment, and all is well again.
Seeing as some specialist test driving the car and wanting £1200 to overhaul the box and I was contemplating buying and fitting a secondhand gearbox (sorry Ian) I think this is a result and makes me appreciate MB engineering even more.
