CK5
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Th400 questions
- Thread starter dixiechevy01
- Start date
dixiechevy01
1/2 ton status
Ah ok thanks. I think the modulator valve itself is probably good its only a few years old but I'll checked it tonight when I get some time to actually work on it. Im thinking the o ring around the modulator valve may be bad and causing it to leak and go to the front of the pan lip.
Do you guys know anything about the rear output seal and bushing, Looks like I'll have to take the tail shaft off to get the bushing out unless anyone knows of any specific tools for pulling it?
And what type of atf does everyone use? just wondering what would be best for performance and budget
Do you guys know anything about the rear output seal and bushing, Looks like I'll have to take the tail shaft off to get the bushing out unless anyone knows of any specific tools for pulling it?
And what type of atf does everyone use? just wondering what would be best for performance and budget
dixiechevy01
1/2 ton status
Well I got the transmission output seal, modulator valve, trans filter and fluid done. Also had to do a rear axle pinion seal. Test drove it and the rear is good no leaks or howling. The trans is still leaking at the front around the bottom of the bell housing so looks like I'm gonna be pulling the trans to do a front pump seal.
Does anyone have any advice for the front pump seal? I know I can probably get a seal kit with the o rings, seals, bolts with seals and bushing, but how hard is this pump to remove and should I be worried about replacing anything else while the trans is out? The torque convertor and flex plate are only a few years old and will probably be in good condition still
Does anyone have any advice for the front pump seal? I know I can probably get a seal kit with the o rings, seals, bolts with seals and bushing, but how hard is this pump to remove and should I be worried about replacing anything else while the trans is out? The torque convertor and flex plate are only a few years old and will probably be in good condition still
Having had a TH400 apart a few times, the front pump can be a bear to get out. Normally I just unbolted it and dumped it upside down, but if you are just doing the pump, probably not an option. On some occasions it would pull out if I rocked it back and forth a bit.
The one thing I can say about the TH400, was that with no special trans tools, measurements, or anything of that nature, I was able to take it apart, put all new clutches, steels and seals in it, slap it back together, and it worked. Never had any issues with replacing seals or anything of that nature. It just seems to be a real "basic" trans to cut your teeth on, nothing overly difficult to disassemble or reassemble, and not real particular on clearances, unlike the more modern transmissions which require a lot of attention to do right. I remember getting the various seals and bushings out with a flat blade screwdriver, and driving them back in with blocks of wood. As I recall I split a couple of bushings on install, but they were cheap at least.
Not that slapping a TH400 together in your garage is "right", the design just seems to be much more forgiving than say, a 700R4 of a novice rebuild.
The one thing I can say about the TH400, was that with no special trans tools, measurements, or anything of that nature, I was able to take it apart, put all new clutches, steels and seals in it, slap it back together, and it worked. Never had any issues with replacing seals or anything of that nature. It just seems to be a real "basic" trans to cut your teeth on, nothing overly difficult to disassemble or reassemble, and not real particular on clearances, unlike the more modern transmissions which require a lot of attention to do right. I remember getting the various seals and bushings out with a flat blade screwdriver, and driving them back in with blocks of wood. As I recall I split a couple of bushings on install, but they were cheap at least.
Not that slapping a TH400 together in your garage is "right", the design just seems to be much more forgiving than say, a 700R4 of a novice rebuild.
The front pump seal will only leak under pressure, the pump o-ring can shrink over time and will leak when the vehicle is not running and sitting.( more likely) The pump will have to be disassembled to replace the bushing and special driver should be used, If it is OK then leave it alone.
If you want to replace the pump oring, remove the pan, remove the pump bolts, and stand the trans up on a 5 gallon bucket with an old flywheel on top. You can stick a screwdriver in between the pump casting and forward drum and pop it up far enough to swap the o-ring, then you can drop it back down into the case without disturbing the other trans internals.
If you want to play it safe you can use the same method and pop the pump all the way out and remove and replace the pump gasket. It is not suggested to use any type of extra sealer, the O-ring and gasket will seal without it. You should use a very light film of grease or vaseline to lube the o-ring surface of the case so it goes together easily.
If you want to get fancy you can get some 4 inch long 5/16 bolts and cut the heads off and use these as guide pins when removing and installing the pump.It will make it easier to not misalign the gasket or pump holes.
If you want to replace the pump oring, remove the pan, remove the pump bolts, and stand the trans up on a 5 gallon bucket with an old flywheel on top. You can stick a screwdriver in between the pump casting and forward drum and pop it up far enough to swap the o-ring, then you can drop it back down into the case without disturbing the other trans internals.
If you want to play it safe you can use the same method and pop the pump all the way out and remove and replace the pump gasket. It is not suggested to use any type of extra sealer, the O-ring and gasket will seal without it. You should use a very light film of grease or vaseline to lube the o-ring surface of the case so it goes together easily.
If you want to get fancy you can get some 4 inch long 5/16 bolts and cut the heads off and use these as guide pins when removing and installing the pump.It will make it easier to not misalign the gasket or pump holes.
dixiechevy01
1/2 ton status
Thanks for the info. I probably wont be rebuilding it right now just gonna do the front pump seals. It shifts pretty good right now, im sure its getting worn out front age but I don't have the money or time to do it yet. As far as the front pump would be a good idea to replace this pump while its off or rebuild it? And I guess I'll have to separate the transfer case from the trans when I go to put it on the bucket. Is'nt there any sort of puller that could be used to remove it? And are there special drivers for the input seal or bushing. Probably wont be replacing the bushing if it not needed, the actual input shaft seal isn't leaking so I doubt theres any play there
