QuestionQUESTION: Hi Vern
I have a `75 Excalibur Phaeton with a TH400.
This morning we started on our holiday, but I could only drive about one hour - 75km`s. Then the gearbox would only let me drive in 1st gear , - or reverse.
The code on the gearbox is 75D401.
Only one wire in to the box, to the kick-down switch.
I have controlled the vacuum ,-no leaks
I tried to remove the kd-wire,-no result
The tranny was overfilled by my garage. Now at the full-mark, still no result...
Help!!!!! Please
Jorn-Erik, Norway
ANSWER: Hi Jorn-Erik:
It sounds like you are experiencing a case of tranny down shift. This usually occurs when the tranny over heats, but most likely is caused by improper overfilling of the tranny. This has not happen on my Excalibur, Phaeton, but it did happen twice on my Rolls Royce. Idiot mechanics just don't know the proper method for serving old vehicles.
1. First, let her cool down, then she if she shifts normally. Then drain two quarts of tranny fluid in a pan. Then start her up again. Make sure there is at least some tranny fluid on the dip stick. If so, drive her for 20 to 30 minutes and check the tranny fluid while she is still hot. If low, top her off while she is still hot to just be low the full level.
2. The TH400 tranny is the best ever made, but when overfilled, she will do crazy things, but will still work. Also, fire your mechanic. He will cause you more problems than good. It is best to research the solution to your problem and then tell the mechanic exactly what needs to be done and how. Then stick with someone that will follow your instructions.
The TH400 tranny was used in Excalibur, Rolls Royce, Cadillacs, Buicks, Audis and many other luxury automobiles, include US military tanks. They didn't make a better tranny in the 70's and 80's.
---------- FOLLOW-UP ----------
QUESTION: Tanks for helping me Vern!!
Panic is not a good feeling! Have been working on the car for almost a year...and then this.
Will the cooling of the tranny automatically make it "re-set", or is there some procedure to follow?
Some "expert" told me to open the small "door" held by 4 bolts on the passenger side of the tranny. The weights abd shaft looked ok to me, although there is not enough room to pull it completely out. Could this be a source of failiure?
If the tranny has to come out...is the only way to pull the motor out as well?
AnswerYes. Normally cooling will reset it unless the problem is caused by something else. Make sure you drain the tranny down to a "below full" level so you can properly check it and top it off once it is hot. If you can't get it out of low gear, then you make have another problem like a bad shift sensor.
