86' 300sdl, i've had it for a year, dad owned it before me 5 years, has a 2 year old vacuum pump, 317k miles on the car, a/c works great, as does everything else, except the transmission. no surprise from what i've read on this forum.
the problem:
when i accelerate hard, it will not shift unless i take my foot of the pedal, it will go up to 3-4k rpm and hold there until i let off the pedal. it does this thru 3rd gear, and is gutless in 4th. i do not engage the kickdown switch under the pedal and get the same result. if i only give half pedal, it will shift hard thru 1-2, but after it shifts to 3rd, the power goes to nothing, the car will actually slow downlike its starving for fuel. i let off the pedal and it will shift to 4th and start to speed up, albeit slowly.
things done:
changed fuel filters(tank screen also)
turned modulator 1/2 turn cw, no help
noticed the alda still has the factory cap on it, i think it has not been adjusted since birth.
gets a new timing chain next month(original also)
cleaned vacuum lines and replaced one cracked t

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rodney

Check for actual vacuum at the modulator and the adjustment of the bowden cable at the trhottle linkage.

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

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

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

i'll get a vacuum tester this week. this has been a gradual issue. when i got the car it shifted correctly but hard. i put in a can of trans-x, that helped a bunch, but over the last 2 months of reading, i found the fluid level can be critical and have made that correct, and the car has degenerated to where it is now. i ordered a new trans filter today, so this weekend will be busy. mobile1 synth trans fluid also. we'll see from there.
adjusted the bowden cable last night, no change

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rodney

You need to get a boost gauge and hook it up in a T to the ALDA line and drive it. Report back on what you find. Make sure you take it above 3K at full power.

thanks brian, i was just reading about that on another thread you posted in.
i'll hit the local schmucks auto and see if they have one on the way home

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rodney

can i use a regular 0-15 psi gauge, plumbed in to check the boost?

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rodney

Of course you can.

10-12 psi from 2500-4500 rpm. whats next

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rodney

Please take it out and warm it up fully. Then run two 0-60 times with it. Find a very flat road. Use a stopwatch.


Report back.

Do you have or can you borrow a Mityvac?

i'll do the 0-60's in the morning. i'll get a vac-pump this weekend. what kind of time range am i looking for?

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rodney

from a standstill i floor it, it runs up to 4300 rpm and the car starts slowing down but the rpm's stay at that point, till i let off the pedal. top speed right now is 78 mph. if i get into o.d. it slows down more. i'm buying a vac pump on the way home tonight.
i drove the car 20 miles after letting it warm at idle for 15 minutes this morning. 34 degree's outside, gauge read right at normal for the car,90c

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rodney

I'd hold off on buying that vacuum pump. Disconnecting vacuum to modulator completely and loosening bowden cable should make the tranny upshift. If not, a vacuum pump won't help it.

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

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

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

Disconnecting vacuum to modulator completely and loosening bowden cable should make the tranny upshift.

if this is so,that means my modulator is bad, right?

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rodney

Can you explain this in more detail?

From a standstill, it accelerates up to a certain speed? What is that speed?

When it reaches 4300 rpm, what is the speed?

The speed won't hold at 4300 rpm? If the speed is dropping from the previous unknown number, how low does the speed fall........to what number?

Something is seriously wrong and there is not enough info to chase the engine or the transmission at this point.

It's possible, but that's certainly not the only liklihood. It's good that you recognize that fluid level is very important. When you change the filter this weekend, cut it open and see how plugged the filter media looks. Also, check to see what type of residue is left in the bottom of the pan. Use a little magnet to see how much of it is steel.

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

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

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