TH400 won't upshift
Thread Starter
Racer
Joined: Aug 2005
Posts: 431
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From: Oita, Japan
TH400 won't upshift
The rpm at which my TH400 would shift was gradually getting higher. A couple of times it stuck in 2nd and would not shift into 3rd. Now it won't shift out of 1st at all. I know nothing about automatic transmissions. Based on threads I found by searching the forum, I thought it might be a sticky governor so I replaced mine but that didn't seem to have any affect.
Any ideas on what to look at now? This transmission was rebuilt before I bought the car (a '72) and I believe it has very few miles on it since the rebuild.
Any ideas on what to look at now? This transmission was rebuilt before I bought the car (a '72) and I believe it has very few miles on it since the rebuild.
Race Director
Joined: Sep 2002
Posts: 10,362
Likes: 5
From: San Diego - Deep Within The State of CONFUSION!
The rpm at which my TH400 would shift was gradually getting higher. A couple of times it stuck in 2nd and would not shift into 3rd. Now it won't shift out of 1st at all. I know nothing about automatic transmissions. Based on threads I found by searching the forum, I thought it might be a sticky governor so I replaced mine but that didn't seem to have any affect.
Any ideas on what to look at now? This transmission was rebuilt before I bought the car (a '72) and I believe it has very few miles on it since the rebuild.
Any ideas on what to look at now? This transmission was rebuilt before I bought the car (a '72) and I believe it has very few miles on it since the rebuild.
- The electric kickdown switch wire is not grounded (or the switch shorted)
- You've got vacuum to the modulator
Let us know what the results of both of those are and we can go from there. Is the fluid level proper?
Melting Slicks
Joined: Jul 2000
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From: Chicago
Thread Starter
Racer
Joined: Aug 2005
Posts: 431
Likes: 0
From: Oita, Japan
SanDiegoPaul -- you are awesome! Thanks for the quick reply. The vacuum line for the modulator was split. I replaced that and it shifts fine now. One other question though -- I unplugged the detent switch to look for shorts. I didn't find any but my detent switch only has 1 prong but I have 2 wires going to the connector (orange and black). Do I have the wrong switch?
Race Director
Joined: Sep 2002
Posts: 10,362
Likes: 5
From: San Diego - Deep Within The State of CONFUSION!
SanDiegoPaul -- you are awesome! Thanks for the quick reply. The vacuum line for the modulator was split. I replaced that and it shifts fine now. One other question though -- I unplugged the detent switch to look for shorts. I didn't find any but my detent switch only has 1 prong but I have 2 wires going to the connector (orange and black). Do I have the wrong switch?
