Rough Upshifts and Jolts at low RPM

[mongrelpom]

Hi there.
Yes, I just bought this W210 E class 250D non turbo with a 722.4 tranny and it does rough upshifting/jolting at low RPM.
I was worried there was some kind of play in the drivetrain, so I put another differential on , the old one leaked anyway, AND RUBBER FLANGE WAS PANTS PIE, and I put new driveshafts on, nice ones, £130 for the pair new , must be from PRC , but the old ones were OK except for notchy outer CV joints and shoddy abs exciter rings.
Anyway, still jolts, so today I pulled off the main hose from the vacuump pump to the brake servo and rammed a conical fitting vacuum tester in, at idle it gives a reading 5 - 15 in Hg erratically pulsing up & down, on increasing engine RPM to 2000 or so it levels out at around 20 in Hg & then as you increase revs higher it goes higher.
Is my pump screwed?

P.S I have blanked off my ERG vacuum as I have blanked off ERG with plate too & jet washed all my intakes out cos I was getting piston scouring
I have refilled my tranny with new dexron 2 mineral fluid, and fully serviced the car. I even drained the new diff and put new 80/90 gear oil in, the old stuff was black.

Oh yes, and 1 other question, I get a little belt squeal at high RPM & I noticed I have a 2083 serpentine belt, should I put a 2080 on, only I was going to do it when I change the vacuum pump, I have ordered both and was going to take the fan off & do both jobs together if my vacuum readings are dodgy? Can't find a Haynes manual for this old rust bucket car, very economic car mind, Im getting over 50MPG at 60MPH

 

[Sp!ke]

Hi there.

I have refilled my tranny with new dexron 2 mineral fluid, and fully serviced the car.

What exact gearbox oil have you put in there exactly? I assume you've double checked the spec?

 

[mongrelpom]

In the tranny -
couldn't get any information so I put
8 litres of dexron II equivalent , it's called ATF Q
I figured it would be OK as the first version of the 722.4 tranny was out in 1984 before the days of Dexron 3, it did the jolt before I put the new fluid in, I just thought it may be that so I changed it.

I threw 8 litres of Carlube 10W/40 semi synth in the engine & changed filter, oil was black the next day, long overdue, poor car.

 

[mongrelpom]

Im worried this jolt may damage my new driveshafts, or strip the diff, it's like being tail-ended, I suspect the vacuum pump but unsure if a fluctuating reading of 5 - 15 In Hg is abnormal. I dont want to change the pump till I know.
Vacuum expert please help

 

[mongrelpom]

Transmission expert please help.
Is a rapidly fluctuating reading of between 5 - 15 in Hg directly from the vacuum pump at idle normal?

 

[mongrelpom]

Found what was causing the nasty jolt & clunk on my merc drivetrain when upshifting at idle - finally.
It was the prop shaft centre support bearing mounting - it was screwed, replaced today
I've been very busy:
Parts replaced (drivetrain)
Driveshafts
Differential & diff oil (2litres)
Rubber flex discs
Transmission mounting
ATF (8 litres)
Transmission Oil cooling pipe that runs below radiator, these are prone to corrosion, this is the only part I had to use mercedes for & it hurt me bad (£63)
(other)
Track Rod end & tracking
Vacuum pump (poor vacuum)
Serpentine belt
Tensioner & damper (had play)
Oil filter an engine oil (8litres)
also, beacause they are only required in California, I removed all unecessary vacuum pipes and transmission upshift delay & disconnected entire EGR system and blanked off EGR with a blank gasket plate & flushed out intake pipes in a jet wash, this stupid system has worn my lovely 5 cylinder diesel engine with piston scouring, at 160,000 she misses on 1 when stone cold now and burns blue oil off that no doubt creeps past piston rings, fine when warm fortunately.
Wired a manual reversing switch and pulled SRS bulb as it is not an MOT requirement, intermittent sensor fault.
Fixed corrosion for a few years, but these are total rust buckets, shame because there is very little else to fault them on
Job done but I left my vacuum modulator on a very soft setting, but I drive the car gently so I figure it's okay, I should really turn it clockwise a bit I know.

 

[mongrelpom]

Most important thing to check first if you have old transmission like me is vacuum mind, buy a vacuum pump, like a mityvac or just a brake bleeding pump and a vacuum gauge with fittings. Then, take the vacuum hose that comes up from the modulator (NOT THE ONE FROM THE UPSHIFT DELAY UNIT) off the green damper / dashpot, ram the pump into the vacuum hose and you should hold vacuum, if not there are 3 options.
Hopefully, someone has not put the cap on the modulator, mine is a white plastic cap that clips in - the slit holes where the lugs are - but the cap can be pushed right down till its flush with the transmission - it locks the t key in place (which incidentally doesnt have to be pulled out to adjust) BUT MORE IMPORTANTLY it seals the vacuum modulator
The other possibility is that your vacuum hose has a leak, bung the bottom end and test again.
Or else, the seal inside your modulator has gone, in which case you have to replace the modulator.
Next step is to test the vacuum supply to the green dashpot/damper from the VCV valve.
This supply should be around 10in / Hg at engine idle., should drop to 0 at WOT.
If it is way out I use the little plastic joins to get supply right, or else I melt an end on one and stick a hot needle through, gives around a 1mm opening, check all the rest of your vacuum system and VCV adjustment before doing this mind.
THE REASON I MENTION THIS IS
If I pull my vacuum system off I get really nasty jolts, clunks on upshifts which sound like they are coming from the rear axle - and they are, even with my new diff, and new axles, and new flex disks & a good centre bearing there is still play in the drivetrain (and my tranny is sweet) there's always some play, it's natural
But it's not here that the problem generally is, normally just vacuum YOUR TRANSMISSION IS SHIFTING WITHOUT USING THE 'CLUTCH' PUTTING HUGE FORCE INTO YOUR DRIVETRAIN - drive like this for too long, especially round town or down streets with speed bumps & you will bust either your CV joints or your Diff

Those little joins are this in internal diameter, used near vacuum source (pump) knock vacuum down to the VCV valve to around 15 In Hg - or more importantly the result should lead to a reading to the modulator of 10 In Hg at idle

Color: I.D. P/N:
Yellow……2.0 mm..……..1162760929
Red……….1.1 mm….…….1162761029
Blue………1.0 mm…………1162761129
Brown……0.9mm….……..1162761429
White……0.8 mm…………1162761229
Green……0.7 mm…………1162761329
Black.....0.6 mm.........____?_____
Orange..0.5 mm.........____?_____

 

[mongrelpom]

transmission modulator images if unsure can be found here on these 2 threads , passenger side of tranny in UK, the drivers side has the upshift delay valve and vac pipe and doesnt control shift smoothness

722.xxx transmission vacuum modulators - PeachParts Mercedes ShopForum

Where is the vacuum modulator? - PeachParts Mercedes ShopForum