My TH400 is shot. Now what?

[yossarian19]

I finally have my '75 Wagoneer running well enough to detect another major issue: the TH400 is now making a hellacious whine at all speeds and all times (didn't do this until recently. Last drive, it was whining. Drive before that, no whine but wouldn't accelerate past 50. This is after a new trans filter. Fluid level is correct)
So I'm guessing the TH400 needs a rebuild.
The dilemma is this: Do I put the money into the TH400 and risk discovering Qtrac issues soon after, do I hunt down a Dana 300 & AW4 combo and spend twice the money but have serviceable parts + overdrive, or do I try to find a TH400 + Dana 20 to swap in and lose the AWD but come away cheaper than the AW4 and have easy parts to find?
I know nobody can make the choice for me but I'm hoping for some perspective or to hear something I haven't thought of yet.

In other news - the Megasquirted 401 runs pretty sweet. Feels [I]strong[I]

[Ristow]

low fluid will cause pump whine. are you checking fluid level with engine running?




also,...are you sure its not the Q-track slipping for some reason? like a missing drive slug in the front or something? the not going above 50 kinda points to that.

[440sixpack]

The TH400 is an excellent transmission and cheap to rebuild. if it needs rebuilt have it rebuilt and drive on .

[Mikel]

Before going to an OD transmission, will your truck benefit from a 30% overdrive? A lot of FSJs are geared much too tall to benefit from an OD.

[yossarian19]

low fluid will cause pump whine. are you checking fluid level with engine running?




also,...are you sure its not the Q-track slipping for some reason? like a missing drive slug in the front or something? the not going above 50 kinda points to that.

I am checking it while it's running. I'll check it again - the rig sat for more than a decade before I got it, it drove onto the trailer and a few miles at under 40 MPH then I tore it down & started the project. I don't want to take much for granted.

I did have the front right drive slug & outer bearing apart.. I would not have thought to check that. I will have to look and make sure it's together right. There are no missing parts, I know that much, so IDK how it would be wrong...

[mattmopar440]

did it start before or after you changed the fluid ??? check the fuild in the QT and put it in E drive see if that fixes the issue if not could be another issue

[yossarian19]

OK, I don't like to be "that guy" but I *hate* when threads die off without resolution from the OP.
I can't say what's up with the driveline. I was eyeballing it because I had no other issues I was aware of except slipping in third and the whine noise came on immediately following my observation of the third gear funkiness.
However, it seems that I have a magical power steering pump. All the fluid I put in it a couple weeks ago? Poof! Gone! It's bone dry in there. I've got nothing on hand but I'll post updates with more findings as they come... I think I found that whine though.

[gsmikie]

i think i have a video that will show you how to rebuild it

[yossarian19]

OK, I haven't found anything new. The PS pump was groaning, sure, but the Jeep is now quietly not working. Takes a good 15 seconds to feel the car bump when i put it into gear (when it does at all) and I generally am not going anywhere when I push the gas.

Is there anything weird about the Qtrac that could be causing this issue, where it feels like the transmission is slipping? It seems to me that even if the center LSD was smoked it should transmit power to one side or the other.

Or might I actually have a bad quadratrac?

Just want to check my assumptions and be sure I'm replacing the right parts.

[DBX11]

I vote in a rebuild vs. reengineering a new setup. Honestly the upgrade swap can?t be any easier than a rebuild.

[letank]

he TH400 is now making a hellacious whine at all speeds and all times


This is after a new trans filter. Fluid level is correct

start with the simplest

With the QT
1) may be the low range shifter has slipped of the high and that expalins the grinding and lack of motion
2) if your QT is OEM, you could have a slip condition, after lack of use, put it in emergency overdrive to lock both front and rear axle s to see if you can move the rig,


back to trans:

May be the filter has slipped and the trans pump is not sucking enough fluid, I forgot the way that the trans filter slip on the valve body, but been there. Hellish sound and no motion...



Yes it is a pain to drain it all to check it, but a good time to install a drain plug on the oil pan.


We need to meet, I was up there 3 weeks ago, around Allegheny Ridge rd, I broke my ankle on FS64

[wiley-moeracing]

and if you are looking for a quadratrac transfer case I have a rebuilt unit with a part time kit, the good chain, ready to go

[rang-a-stang]

Me and Heavy_Metal_Thunder_81 just bought a TH400 from a guy here in SoCal. Heavy_Metal_Thunder_81 needs the case. I need the dipstick. You can have, literally, EVERYTHING inside the trans for $50 plus shipping.

[yossarian19]

This thread is going off the rails with all the new variables I am coming up with.

I did find the vacuum modulator wasn't hooked up to anything. Since when? Was it always unhooked? Did I do that when I tore things down and forget to hook it back up?

Who knows.

The front pump of the trans was leaking badly, though, so I got the trans out to re seal it. I'll look at the frictions while I'm at it. The power steering whined too but the sound of hellspawn was, indeed, coming from the transmission.
I'm also going to take the pan back off and poke around the valve body. Since it sat for so long there is a decent chance the shift valves are gunked / slightly rusty. I'll clean them (carefully!) and reassemble maybe with a shift kit.
If it needs friction, I'm hiring it out. If it doesn't, I'm putting it back together, hooking up the vacuum modulator and taking it for a drive.

I read that the reverse and 3rd gears both work off the same clutch bands, so I don't have a problem there because I do have reverse that feels fine, even if a little sluggish to engage (same as first). Slow to engage kinda points at gummy valve body, maybe?

I'm gonna look at the cost of replacing the governor & vacuum modulator while I've got it on the bench.

Also - degreasing a 40-odd year old transmission is GNARLY. I recommend using the contents of an old, salvaged Jerry can. Ten year old gasoline works a hell of a lot better than any commercial degreaser I've found but the headache and flammability concerns are real.

[rang-a-stang]

There's this, too:

http://www.ifsja.org/forums/vb/showthread.php?t=186004