I'm wanting to "tune-up" my transmission on this 190K car. I plan to convert to synthetic fluid. I would like to drain as much as I can, TC included, change the filter and re-fill with synth. I also am planning to use a bottle of trans-x as I've heard good things about this stuff.
Should I plan to change the fluid again shortly after the switch due to the tranny being cleaned by the synth? How long should I wait?
Will I spring any leaks by switching to synth. The tranny does not leak now.

My reason for doing this is I'm getting a bit more flare than I like and occasionally it downshifts hard on braking. I'll be checking the line from the modulator and the bowdoin (sp?) cable if the car has one. The car is subject to hi-speed 80 miles per day and I need for it to keep working this winter.

Any warnings, tips, advise greatly appreciated.

Thanks.

I just did what you plan on doing. Yes, run trans-x, yes change the filter and pan gasket, yes change your fluid again in 300 -500 miles, yes go synthetic, no I did not develop leaks, it stopped them. Also clean all t fittings and vacuum lines going to tranny. I also adjusted Bowden cable. Tranny will always shift hard compared to Jap or American cars. Good Luck, keep us posted....

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1984 300D Turbo Sedan (Hilda) 272,115 miles.....
Anthracite Gray/Palamino Leather, I am 3rd owner

2001 Dodge Stratus (Silver) (wifes) 55814 miles...

1982 280TE Wagon Astral Silver Metallic/
Anthracite Velour
260,512 miles (Eva)

1969 230 Sedan Olive Green/Black MBTex
4 Speed Manual
84,213 miles ????
Haus Frau


2004 Boreem Ninja Pocket Bike
Highly Modified 49cc (Ling Ling)

Einigkeit und Recht und Freiheit

The (down)shifting hard on braking may well be caused by insufficient vacuum to the modulator as it shifts down. This could be your vacuum control valve being worn out or misadjusted or any number of vacuum leaks resulting generally in low vacuum. I finally figured this out a few months ago and got mine to downshift properly. Then a few weeks later it was doing it AGAIN- but at the same time the brake boost became erratic and the vacuum shutoff became slower. I replaced the brake booster with one from my parts car- no difference. After scratching my head for a while and just listening around the booster as it was shutting down, I bought a rebuilt brake booster. That solved all the vacuum problems and now the car shifts, brakes and shuts down properly

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80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)

My 300sd transmission is really noisy when I brake hard from high speed coming up a highway ramp and the tranny starts to downshift. Each downshift makes a clunk noise. Is this a similar problem to your? I just changed fluid and filter and added BG transmission conditioner. No change. I would like to know how to solve this problem on my car too.