I replaced every rubber vacuum line I could find under the hood of my 87 300D. Now the shifts are really harsh. Lot's of horrible clunks and pop's from the rear end during normal shifts. If I accelerate moderately the shifts smooth out a bit. The down shifts are harsh as well.

Before the replacement of the vac lines the shifts were pretty good with the exception of the transmission kinda not knowing what gear to be in sometimes.

If I had this problem with my SD I would adjust the modulator to smooth out the shifting... I looked under the 300D today and could not see a modulator to adjust.

The shifts now feel very firm and good. The shift points are spot on as well. It just the darn rear end noise

Thanks

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08 R320 CDI current

Past
95 E420
87 300D Turbo 5spd
90 300TE
83 300SD
85 300TD
92 400E
85 190D

The modulator is on the driver side of transmission as it is in the 83 300SD.

The vacuum control valve (VCV) is on the side of the IP. There are two vacuum lines attached to the top and a black vent line on the side. To set, loosen the two bolts that take a 10mm wrench holding the VCV to the IP, turn the VCV all the way CCW, prop the throttle linkage at WOT, slowly turn the VCV CW until you just feel resistance, tighten the bolts.

Sixto
87 300D

I will give it a try. Thanks

On a side note....


I have not driven the 300D in a while until today... OM603 always puts a smile on my face. I wonder what 200ish HP would feel like

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08 R320 CDI current

Past
95 E420
87 300D Turbo 5spd
90 300TE
83 300SD
85 300TD
92 400E
85 190D

Would feel like a big hole in your wallet

Sixto
87 300D

You know I didn't trust this advice at first... I was having good luck adjusting the "advance" of this VCV and even wanted to turn it CW beyond max - because I had what I thought is unusually high 15 inHG vac at idle and wanted to bring it down to around 10... to reduce the range of vac from 10-0 going to the vac amplifier...

Anyway, I had my IP off this weekend and I see that the VCV pivots on the exact same axis as the go-pedal linkage on the other side of the IP. If you over-rotate the VCV clockwise beyond the 'resistance point' what you are in fact doing is not permitting the the accelerator to reach it's bump stop limiter. You're not allowing max input to the IP. Even though you might be allowing vac to drop sooner with this strategy, maybe to help your shifting, you take away top end power.

I believe now.

Sixto I wish you gave a short version of this reason as to why you don't go beyond the resistance point in your accompanying good advice, then schmeebs like me would probably attempt fewer dumb things...

Put the VCV in its right spot and I'm seeing a good healthy drop from 15 or so to zero, on warm engine, with turbo pumping... So I'll leave it there and move on to the next thing in trying to get the gremlins out of my shifting. Too soon upshifts, a little soft, 2-3 and 3-4 too close together.

Bowden cable, white nut, that's next... Before I go crawling for a modulator under the car.

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Cheers!
Scott McPhee

1987 300D

I was thinking about just that. Seems to me an alternative way to set the VCV is to turn it full CW with the throttle at WOT then let the negator spring turn it back CCW until the spring is relaxed. That ensures you don't inadvertently set it as a throttle limit.

But what I posted is basically all the FSM tells you about setting the VCV. Maybe there's more discussion in the IP section.

Sixto
87 300D

I did the adjustment today. Seemed to help out a lot. I am still have a clunk in the rear end area. I have yet to have this car on a lift, I have never even really looked under it. This Saturday I will get it on a lift to replace a tie rod.

I am going to look at the flex disk's and halfshafts. To me those two things sound like the culprit. Kinda sounds like an old American car that needs U-joints real bad.

Sound like a good plan of attack?

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08 R320 CDI current

Past
95 E420
87 300D Turbo 5spd
90 300TE
83 300SD
85 300TD
92 400E
85 190D

My guess on the clunk is the diff bushings are shot. Those would be the two you can see from behind the diff. The left one takes a heck of a beating. If the bolt isn't centered in the bushing, it's gone.

Sixto
87 300D

So it sounds like the rear diff mount/set up is not the same as my SD. I can't wait to get it on the lift later in the week.

Sixto your a wealth of information-Thanks

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08 R320 CDI current

Past
95 E420
87 300D Turbo 5spd
90 300TE
83 300SD
85 300TD
92 400E
85 190D

Goodness, very not the same. A complete PITA to replace them too. Diff has to come off! There are a couple of bushings atop the snout of the diff.

Sixto
87 300D