TH 400 trans locked
October 15th, 2008, 05:39 PM
#1
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Join Date: Oct 2008
Posts: 2
TH 400 trans locked
I had a 400 trans in my garage for a few years now and I am going to swap it with friend for a 700r4 with a bad case of cooked clutches for another project.
Problem is the 400 is stuck in what I assume is forward gears no matter where the selector shaft is positioned other than PARK.
The output shaft will only spin in 1 direction in any gear including neutral. The PARK position seems OK.
The trans sat for a few years in a garage, but was working fine when removed from the previous vehicle.
It makes a definite mechanical "bottoming" noise when you attempt to spin it the other way.
Maybe just stuck clutches or a band from sitting?
Thanks for any input.
Problem is the 400 is stuck in what I assume is forward gears no matter where the selector shaft is positioned other than PARK.
The output shaft will only spin in 1 direction in any gear including neutral. The PARK position seems OK.
The trans sat for a few years in a garage, but was working fine when removed from the previous vehicle.
It makes a definite mechanical "bottoming" noise when you attempt to spin it the other way.
Maybe just stuck clutches or a band from sitting?
Thanks for any input.
October 16th, 2008, 08:01 AM
#2
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Join Date: Jul 2007
Location: Edmond, OK
Posts: 15,902
If you've checked all of the obvious stuff (linkage, fluid level, etc.), I would say that you have an internal problem. The TH 400 uses a band to hold the ring of the sun and planetary gear set for reverse. Perhaps this band isn't engaging or is bad.
October 16th, 2008, 02:54 PM
#3
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Join Date: Oct 2004
Location: Southern CA
Posts: 2,212
Hard to do, when the trans is not in the car.
Not possible for that to happen without pressure in the system. Pressure, that is supplied by the pump when it is turned by the engine.
I see one, or both, of the sprague (one way) clutches as a possibility.
Talk to your local trans rebuilder to find out for sure.
Norm
Not possible for that to happen without pressure in the system. Pressure, that is supplied by the pump when it is turned by the engine.
I see one, or both, of the sprague (one way) clutches as a possibility.
Talk to your local trans rebuilder to find out for sure.
Norm
October 16th, 2008, 03:13 PM
#4
Old(s) Fart
Join Date: Mar 2007
Location: Northern VA
Posts: 47,311
For complete correctness, it's a sprag clutch.
October 19th, 2008, 06:05 PM
#6
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Join Date: Oct 2008
Posts: 2
Thanks for the suggestions, I'm thinking the forward or intermediate clutch is frozen since the output shaft does turn in 1 direction.
I guess I'll be tearing the trans down for an exploratory looksie.
Thanks again guys.
I guess I'll be tearing the trans down for an exploratory looksie.
Thanks again guys.
November 10th, 2008, 01:27 AM
#7
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Join Date: Nov 2008
Location: California
Posts: 4
When you say "spin" do you mean turn freely by hand? It is normal for a turbo 400 to turn in one direction easily and the other very diffucult. This is because the reaction carrier is fighting with the low sprag, low roller after '70. If you have the transmission output yoke handy it will turn both ways but one will be harder.
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