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+--- Thread: Question about the vacuum on auto transmission (/showthread.php?tid=3264)
Question about the vacuum on auto transmission - fehron - 01-11-2012
I'm working on my 82 240 auto and have multiple vacuum leaks, in trying to track them down, one of them is in the transmission circuit that reads throttle position telling the transmission how firm and when to shift. What I've learned is that with no vacuum the transmission acts as if it's at full throttle shifting to second at approx. 25mph then to third at 40mph and no sooner, even if I let off the throttle. On the other hand, bypassing all the other vacuum stuff and going directly to the transmission, it shifts very early and soft even at full throttle. The line on the transmission had a bad connection so I fixed that and with a solid connection it still bleeds vacuum at the transmission.
What is that part called? Is it a solenoid or is it a valve or modulator? Should it leak vacuum at a determined rate or should it maintain vacuum? I guess I need to know if mine is bad and what it's called so I can order the part and replace it.
RE: Question about the vacuum on auto transmission - willbhere4u - 01-11-2012
vacuum shift modulator
RE: Question about the vacuum on auto transmission - fehron - 01-11-2012
Thanks man. Do you have any idea about testing it. Can I replace a seal or does the whole thing have to be replaced.
RE: Question about the vacuum on auto transmission - willbhere4u - 01-12-2012
I'm not sure I know you can test them.
I don't know the procedure you probably need a vacuum gauge tee'd in to the line? there's probably some good info out there on Google
RE: Question about the vacuum on auto transmission - Hercules - 01-12-2012
Start at modulator,connect test hose to plastic vac. fitting on modulator, should hold vac. Two styles of modulators, Black rubber cap style,ck rubber cap, flexible,and not cracked,( replaceable ). Hard plastic cover style, ck. seal under cover.If these ck. ok, replace modulator, readjust. Yes you are correct,Shifting controlled by vacuum modulation Only.
Adjusting engine throttle linkage for best performance. Engine( off ) depress throttle to full,CK.injection pump at max.Remove air filter Top ck. throttle blade.NOT to be at full open. Engine performance drops with a loss of manifold air speed. Air blade Midway between 3/4 and full. Test drive and readjust more or less for best. Good luck.
RE: Question about the vacuum on auto transmission - fehron - 01-12-2012
I have the hard white plastic one. The nipple where the vacuum goes in swivels.
With my vacuum hand pump, one squeeze brings it up to 5-6 inHg, which quickly leaks down before I can squeeze again. So, I'm thinking it's the seal. Thanks
RE: Question about the vacuum on auto transmission - fehron - 01-12-2012
Wow, I can't find the seal by itself. Is it even available alone? Lots of online sites offer the modulator itself but not the seal for the w123. Can someone point me in the right direction?
RE: Question about the vacuum on auto transmission - Hercules - 01-18-2012
Most likely not listed,try seal assortment kit (metric). Note modulators become old and stiff,poor shifting occurs,can not be adjusted properly. Good luck.