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BiggieFL

3spd auto questions

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I have a 1982 928 with auto trans that I recently bought in November and have put about 400 miles on it. Car has 77k on it and trans was rebuilt in 2001 about 3k mles ago. Problem is I don't want to drive it to mechanic(20mins away) being I may damage it so here goes. When cold/warm the trans works perfect in drive. Once hot she will slip if I give her too much gas but only really in 2nd gear. Anotherwords if I mash it at a light it will pull hard in 1st to about 4800 but then slip/slide going into 2nd. 2nd seems to hunt unless past where it would want to downshift into 1st(below say 50mph). In 3rd it works fine on freeway but at lower speeds it will slip into and out of 2nd if I give her more than 1/2 throttle. Again, highway speeds in drive is perfect as long as I don't give TOOO much throttle so normal driving at 70mph she is great. Fluid level is correct and red, not brown. Now the kicker is...it works perfect if shifting manually. If I put it in 1st it will stay and pull like a train. When I shft into 2nd it stays and pulls. If I am in 3rd and downshift manually into 2nd and mash it she will pull like a train to redline(110mph?) then stick it in 3rd and roll down the road. Anotherwords I think the trans itself is fine but something in the valve body might be bad or ??? Is this vac operated? What should I check and look for? I will do a filter and fluid change but again I hate to drive it if it is something stupid like a vac line.

When in drive it will not upshift to 2nd until about 2500 even if I let off the gas, more so when cold. Not concerned about that, just wanted you to know. I will buy a trans filter kit as well but hate to waste the $$ if you think she needs to see a trans guy. I am a pretty able wrench turner but this car as you know is not exactly textbook.

Thanks, Nick

Edited by BiggieFL

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you do have a vacum modulator. the line is rubber at the trans and at the intake, a solid line in between. check for vacum first before tearing in to it

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you do have a vacum modulator. the line is rubber at the trans and at the intake, a solid line in between. check for vacum first before tearing in to it

Will check this weekend...thanks!

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Ok car is on stands and vac to modulator is good. Modulator also holds vac as well. I am going to adjust modulator and then I am out of adjustments except for kickdown. Now when I press down the pedal it goes almost all the way to floor before it clicks, is that normal or should it click at about 2/3's-3/4 throttle?

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Ok car is on stands and vac to modulator is good. Modulator also holds vac as well. I am going to adjust modulator and then I am out of adjustments except for kickdown. Now when I press down the pedal it goes almost all the way to floor before it clicks, is that normal or should it click at about 2/3's-3/4 throttle?

Google this > mercedes transmission b2 piston

yes, Mercedes

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Check for vacuum at the modulator valve with the engine running. Interesting that you don't want to drive the 20 miles to have a professional transmission garage look at it but drive the clappers off it.

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