TH400 seized? And has drive in all positions?

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Nikkormat
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TH400 seized? And has drive in all positions?

Post by Nikkormat »

Have you ever had one of those days? Well I'm having one and it just got worse. :banghead:

I started the Cherokee up to move it to the other side of the driveway only to come to a sudden stop and the stench of burnt transmission. :banghead:

I put it in reverse, no reverse. Jeep loads up like it's trying to move forward. Put it in drive, and it will creep forward with the pedal on the floor against the converter at 2500 RPM. That's much higher than its stall speed. In park it loads up like it's trying to move forward. If I put it in drive, and turn off the engine, even on a very steep hill (roughly 16% grade) it will not roll. :banghead:

What the heck did I do? Trans is full of fluid, shift linkage is connected, and it's been totally trouble free till now.
Gabe, "reformed" Jeep hoarder.
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berettajeep
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Re: TH400 seized? And has drive in all positions?

Post by berettajeep »

Can't answer your question but I am more nervous for my transmission now.
'47 CJ2A My build
'74 Cherokee S 401/auto My build
'94 Cherokee 4.0 5 speed
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Curly
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Re: TH400 seized? And has drive in all positions?

Post by Curly »

Pull the pan and look at the manual valve.It is attached to the shift linkage, and moved by it. It selects the different gears. If the linkage has come loose inside the pan, the valve could be in the wrong spot. Had it happen once on a Powerglide auto trans.

Curly
I start what I finish.

81 Wagoneer 4.2/auto
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csuengr
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Re: TH400 seized? And has drive in all positions?

Post by csuengr »

I remember reading on here someone else having the same issue and it was the linkage inside the pan.
1977 Cherokee S, Ford 5.0, 5 speed, BW 1356, 33 x 10.50 BFG's. No longer my DD.
2007 Mercury Milan, 2.3L, 5-speed, now my DD. 29 mpg average.

letank
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Re: TH400 seized? And has drive in all positions?

Post by letank »

may be the modulator is toast. you can plug the vacuum nipple on the modulator on the passenger side of the trany. and block the vacuum coming from the engine side.
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (229 Kmiles... the running test lab)

Topic author
Nikkormat
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Re: TH400 seized? And has drive in all positions?

Post by Nikkormat »

It's not the shift linkage in the pan, if it was I wouldn't have the parking pawl and the reverse band wouldn't apply.

I think the reverse band is partially applied in all gears, kind of like a transbrake. How is that possible? How could it stay stationary in gear without the pump running to hold the bands?
Gabe, "reformed" Jeep hoarder.

csuengr
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Re: TH400 seized? And has drive in all positions?

Post by csuengr »

Nikkormat wrote:It's not the shift linkage in the pan, if it was I wouldn't have the parking pawl and the reverse band wouldn't apply
Without actually looking, you don't know that. It could be an issue with the internal linkage or the comb. It is a cheap diagnosis.
1977 Cherokee S, Ford 5.0, 5 speed, BW 1356, 33 x 10.50 BFG's. No longer my DD.
2007 Mercury Milan, 2.3L, 5-speed, now my DD. 29 mpg average.
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ClovisMan
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Re: TH400 seized? And has drive in all positions?

Post by ClovisMan »

Transmission fluid baths suck! Try the modulator bypass thingy first from above. I hate pulling the pan!!
88 Grand Wagoneer - The Money Pit - 360/727/NP208 - SOA/SF - Lots of other stuff SOLD
78 Cherokee Chief - Copper - 360/TH400/Quadratrac - 4 inch BDS lift - 33 inch tires SOLD

FSJ Guy
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Re: TH400 seized? And has drive in all positions?

Post by FSJ Guy »

A bad vacuum modulator can cause all sorts of problems. X2 on checking/bypassing it.
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Grand_Wag_85
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Re: TH400 seized? And has drive in all positions?

Post by Grand_Wag_85 »

My 76 did this. Forward in every gear including park EXCEPT it was park and drive at the same time. Reverse went forward and had reverse lights on. Never did figure out the cause, just swapped the trans.
82 J10
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You know it's bad when your car is on the EPA's 10 most wanted list!

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Nikkormat
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Re: TH400 seized? And has drive in all positions?

Post by Nikkormat »

Grand_Wag_85 wrote:My 76 did this. Forward in every gear including park EXCEPT it was park and drive at the same time. Reverse went forward and had reverse lights on. Never did figure out the cause, just swapped the trans.
Did you send me all of your FSJ demons?
Gabe, "reformed" Jeep hoarder.
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Grand_Wag_85
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Re: TH400 seized? And has drive in all positions?

Post by Grand_Wag_85 »

Nikkormat wrote:
Grand_Wag_85 wrote:My 76 did this. Forward in every gear including park EXCEPT it was park and drive at the same time. Reverse went forward and had reverse lights on. Never did figure out the cause, just swapped the trans.
Did you send me all of your FSJ demons?
I had to pawn them off on somebody. I've been stashing them down by the RR tracks in Leadville all of these years and they needed a sacrificial FSJ to latch on to :p


I definitely had a lot to do with the death of my TH400. I'll have to share that story with ya some other time.
82 J10
77 J10 Golden Eagle 401
88 GW

You know it's bad when your car is on the EPA's 10 most wanted list!

Topic author
Nikkormat
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Re: TH400 seized? And has drive in all positions?

Post by Nikkormat »

Manual transmissions from here on out.
Gabe, "reformed" Jeep hoarder.
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Grand_Wag_85
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Re: TH400 seized? And has drive in all positions?

Post by Grand_Wag_85 »

Preach it!

Just gotta mate it with the QT :D
82 J10
77 J10 Golden Eagle 401
88 GW

You know it's bad when your car is on the EPA's 10 most wanted list!

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Nikkormat
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Re: TH400 seized? And has drive in all positions?

Post by Nikkormat »

Grand_Wag_85 wrote:Preach it!

Just gotta mate it with the QT :D
NP219 or NV242!
Gabe, "reformed" Jeep hoarder.
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Grand_Wag_85
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Re: TH400 seized? And has drive in all positions?

Post by Grand_Wag_85 »

Nikkormat wrote:
Grand_Wag_85 wrote:Preach it!

Just gotta mate it with the QT :D
NP219 or NV242!
BW1339, Jerrari style.
82 J10
77 J10 Golden Eagle 401
88 GW

You know it's bad when your car is on the EPA's 10 most wanted list!

Topic author
Nikkormat
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Re: TH400 seized? And has drive in all positions?

Post by Nikkormat »

Ok, I had a little spare time today. I bypassed the regulator with no change. Checked flow of cooler, the pump is running. I believe the valve body gasket has failed.
Gabe, "reformed" Jeep hoarder.
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Tatsadasayago
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Re: TH400 seized? And has drive in all positions?

Post by Tatsadasayago »

The TH400 has a known issue with the main valve body valve breaking in half causing this very issue. Think Trans-Brake action.
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Topic author
Nikkormat
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Re: TH400 seized? And has drive in all positions?

Post by Nikkormat »

Tatsadasayago wrote:The TH400 has a known issue with the main valve body valve breaking in half causing this very issue. Think Trans-Brake action.
Is that the manual valve?

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Topic author
Nikkormat
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Re: TH400 seized? And has drive in all positions?

Post by Nikkormat »

Anybody have more wisdom to offer on the manual valve before I tear into it this week? Will the valve body have to come off or just the rooster comb/shift shaft?
Gabe, "reformed" Jeep hoarder.
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