300d turbo transmission won't shift

Hi all: My tranny started a major problem in the last week and I'm trying to figure if it is replacement time or could it be something simple. Basically I am cruising along at 50MPH and it suddenly downshifts to 2nd gear. Sometimes it will shift up to 2nd gear and go no further. Oil level is fine. Vacuum at the main line is 20 lbs. but I don't know how to test further. Linkage looks OK and is not sloppy. I would appreciate any ideas. Should I just start looking for another transmission? Thanks Tim

[leathermang]

Cheap possible cure is to change fluids and filter and put in Trans-x...
use search feature to read about Trans-x....

[Shellnekov]

Unhook line to tranny from vacuum release pot then as you give throttle vacuum should go down, when 2 pins are 10mm apart vacuum should be 5-6. If not adjustment is needed.

[Tirebiter]

Don't forget to check/set the line pressure at your modulator. This can make a world of difference in an old box with internal leaks.

[JamesStein]

The '84 300CD I bought had a similar problem.

Fluid change (including converter), filter change and trans-x and it shifts like a tranny with 100k miles on it .

When I drained the fluid out... I learned what burnt transmission fluid actually smells like.

In fact, that reminds me.. I wanted to do a 2nd fluid change after a thousand miles to be sure I got all of the nasty stuff out. its been about 1k miles.. time to do it again to make sure I get all of that old worn out fluid out.

Thank you for the replies. I drained about a quart of tranny fluid and replaced it with Trans-x. Am starting to drive it today- have driven it about 12 miles and it seems to be working fine. I think it's a little early to celebrate but I am optimistic so far. I was planning to run it for a few weeks with the trans x and then replace the oil and filter. Will post an update. Tim

[jfikentscher]

Tim C,

UPDATE????

Joe

[tomm9298]

My tranny was also shifting, and not shifting, weirdly. I bought this stuff at Advance Auto that was for A/T. It was as thick as honey, yet the proper color of red. Seems to have done the job. Shifts GREAT now.

[jfikentscher]

Yesterday the 87 would downshift if i got the speed up to about 50, then it started not shifting higher than second.It also seems to slip out. Going to try trans-x. where should i drain from??

Joe

[leathermang]

The easiest deal is to get some clear tubing....like 9 feet worth....of the largest size which will fit into your trans dipstick tube ( with some air space around it... for syphoning or sucking you have to allow air to take up the space evacuated by the fluid ).... a Mityvac could be used to start it... although I did not... get clear so you don't have transmission breath afterwards... LOL .... just get it started as far as the side of the car and stick it down into a gallon bottle.... then go take a break because it does not drain fast....

[jfikentscher]

LEATHERMANG,

Thanks. I'll try it this afternoon, and update after the procedure.

Joe

[jfikentscher]

trans-x not available in our area? None of the local shops carry it!

[jfikentscher]

Found some Trans-x at the NAPA parts store. Limped there at 25mph in second gear, got back, now draining oil per above instructions from leathermang. Fluid capacity listed as 6.5 quarts so one can should do.
3:10, Man this stuff drains slowly!!!

Joe

Update on '84 300 D turbo. Ran the Trans x for a week or so and then changed the oil and filter (Mobil DexronIII) Also changed the main vacuum line as I broke it when trying to remove a tube (very brittle), The fluid in the pan was a little dark. There was no metal in the pan. Transmission shifts very nicely now. I am not someone who believes in snake oil but... Trans x worked for me. Best to all. Tim