Ok the SDL is out of storage after 7 months, and everything, knock on wood every single thing on the car still works perfectly. Well except the trans is slipping all of a sudden. Almost 254k, and 19 years I wouldn't be surprised if its time. Who rebuilds these and does a good job?

Here are the symptoms,the shift that slips the most is 3-4 I think, but it slips a bit between all the gears. Seems to be rpm sensitive. 2k and down is fine, and 3k and up is fine. The trans shifts funny between 2k-3k. Its slow to shift and the rpms will shoot up a bit between shifts. Downshifts feel kind of funny too, but I can't put my finger on it, just doesn't feel right. Overall something just doesn't feel right. Had the trans out last year to replace the front seal. That went well, drove it for 6 miles and all was well. This problem is recent.

Any ideas? I checked the temp circuit and that is working, so it isn't electronic. This seems like a vac problem. We followed the trouble shooting procedure in the FSM for slipping between gears. But the results were in conclusive, further trouble shooting is needed.

I'm just going to nurse it and if it isn't vac related I'm going to swap in a rebuild in a month or two. I need this car to run, don't have time to mess with it like this.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

You already know that it's highly likely that it's vac related. And, you also know that the typical shop makes a killing from people with exactly the same problem by replacing their entire transmission.

Therefore, it certainly makes some sense to carefully look for a high vacuum condition to the modulator. Lacking this as the culprit, it makes sense to get a proper gauge and determine if the modulator pressure is correct.

Why replace a perfectly good transmission if it simply requires adjustments?

Of course I am in no hurry to spend $1,500 rebuilding the trans. This is plan B, plan A is to figure out the vacuum problem, if thats the case.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

High vacuum from the amplifier to the modulator?

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Camper
83 300D
87 300 SDL
96 E300

Yep, that will cause it.

See what the vacuum to the modulator is while driving it under varying modes of operation.

I'm just going to disconnect the trans from the vac line. When it loses vacum the trans will bang into gear. I found this out last year when I knocked a vac line lose. So if I disconnect a vac line and it bangs through all 4 gears I'm good I need further trouble shooting with the vac tester. If the slip remains, its probably a clutch pack problem.

I did trouble shoot the modulator and it seems to be pulling vac within spec. Will test again.

Further trouble shooting is needed, stand by for an update.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Slipping between all gears would tell me it's not an internal problem at this time. Could be pump too, but doubtful. If the vac issue doesn't play out, I'd check line pressure on the unit.

Vac amp is the blue UFO looking thing right?

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Why not start with about 1/2 turn CW of the modulator adjustment?

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

You may very well need a modulator adjustment, but you need to check on the vacuum supply to it first. The modulator is the least likely to be the one component that has "changed".

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1982 300CD Petrol/Black Leather

After 19 years it is about time to replace ALL the rubber vaccum connections, if you haven't already done so....real cheap as opposed to a 1500 buck tranny!

The Brian Carlton EGR valve fix did wonders for my shifting...been there yet??

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Mark
1983 300TD Wagon
Even a broken watch is right twice a day

OK disconnected the vac line from the modulator, and all of a sudden shifts perfectly. Couldn't ask for better shifting. So its a vac problem! Now I just need to track it down. Still working on it, round 3 tomarrow night. Thinking it may have something to do with the vac amp, or modulator.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

thanks to this list I got alot of info to obsess over and messed with my bad shifter for several weeks!
after TOO MANY trips around the block I have a perfect shift on a 240k tranny! My final "TWEEK" involved the modulator!

DILIGENTS seems to always pay off with these fine machines!

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[B]AlanT
BELEN NM


93 dodge cummins truck~old reliable
01 Volvo AWD XC70 Turbo Wagon
74 450 SE on the way out!
Recent: 1972 Toronado 56k on the clock!

IF it plugs in, lights up, makes noise,
I'M ON IT!

Finally had some time to look at the SDL and I disconnected the line from the VA to the MOD the line with the green items on it, and the vehicle shifted normal and no more flare. So it is a vacuum problem, where or what should I check for to deal with the vac problem.

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Camper
83 300D
87 300 SDL
96 E300

You need to put a vacuum gauge in the line to the Modulator and drive the vehicle to see how much vacuum you have at various operating conditions.

Normally, the SDL will have about 10" of vac at all times, unless you get past 1/2 pedal. Then it drops steadily toward 5". If you get into heavy boost, the VA reduces the vacuum further down close to 1".

My guess is that either the VA or the VCV is not working properly and the vacuum is too high.

I had a "transmission slip" the other day as well, but I don't know if it was a transmission slip. It happened 2 days after changing my fluid at 90k just for regular servicing. It was in the rain, doing about 25 mph and accelerating, and suddenly for just 2 seconds, it was like I hit ice. The car revved higher. I thought maybe I hit a slick spot on the road. Then about 4 days later, going UPHILL nonetheless, about 25 and accelerating, in the rain again, the engine revved higher, but this time I saw the speedometer going from 25 to 45 in just a few seconds. Some wrote back to me that had the transmission slipped, the speedometer would not have gone faster. Did your speedometer go faster as well?

1991 300d