TH400 Information Thread

[bucket]

What is the chances that the separator plate gasket can be reused? 15 years old, but probably only 1000 miles on it. Basically, what parts should be on hand before tearing into it?

 

[NickTransmissions]

What is the chances that the separator plate gasket can be reused? 15 years old, but probably only 1000 miles on it. Basically, what parts should be on hand before tearing into it?

Unless the check ball seating locations are heavily worn and/or plate warped, damaged it should be reusable. I wouldn't buy any parts before you get it apart and on the bench...This way you can inventory everything you need and buy only those parts, unless this is your only vehicle...If that's the case, have a composite pan gasket (no cork), a set of valve body gaskets (case-spacer plate and spacer plate-valve body), a detent solenoid, in case the original was not replaced when it was rebuilt last, perhaps a few spare 1/4 check balls in case you lose one or two and filter o-rings (there should be two o-rings on the case side of the filter's pick up tube).

If you're very careful, the valve body gasket set that's on there now should be reusable; same for the pan gasket if it's not cork or standard rubber.

If you do find that one or more check ball seating locations are very worn out, you can repair the plate using Fitzall's plate repair kit and a 1/4" drill bit.

This video shows the process/procedure...The plate shown is out of a 4L60E but that kit will service all plates that use 1/4 check balls.

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[idahovette]

^^^^^I laughed when Nick said "if this is your ONLY vehicle"^^^^^^^^^ It's a toss up whether @bucket has more vehicles or kids!!!!!!!

 

[AuroraGirl]

Unless the check ball seating locations are heavily worn and/or plate warped, damaged it should be reusable. I wouldn't buy any parts before you get it apart and on the bench...This way you can inventory everything you need and buy only those parts, unless this is your only vehicle...If that's the case, have a composite pan gasket (no cork), a set of valve body gaskets (case-spacer plate and spacer plate-valve body), a detent solenoid, in case the original was not replaced when it was rebuilt last, perhaps a few spare 1/4 check balls in case you lose one or two and filter o-rings (there should be two o-rings on the case side of the filter's pick up tube).

If you're very careful, the valve body gasket set that's on there now should be reusable; same for the pan gasket if it's not cork or standard rubber.

If you do find that one or more check ball seating locations are very worn out, you can repair the plate using Fitzall's plate repair kit and a 1/4" drill bit.

This video shows the process/procedure...The plate shown is out of a 4L60E but that kit will service all plates that use 1/4 check balls.

xc_hide_links_from_guests_guests_error_hide_media

by composite do you mean an elastomeric gasket with 2 lines of perimeter o rings on each side?

 

[NickTransmissions]

by composite do you mean an elastomeric gasket with 2 lines of perimeter o rings on each side?

Those are also great but I'm referring to the pan gasket that comes in the TransTec and Transtar paper and rubber kits.

 

[Tonimus]

@NickTransmissions Wonderful thread sir. I've had your rebuilding videos on while working at my desk to absorb some knowledge by osmosis.

I think I've learned enough to ask a less uneducated question. Long story short, the TH400 in my '78 burb needs a rebuild. Going to do a full drag race rebuild on it and toss it in my '78 Camaro. I currently have a 3500 stall converter and a Hughes TH350 35-1X which is good to 750hp, but I'm coming up on that soon. Additionally, I want to do a transbrake. The question is if I'm staying under 1k hp, what parts and specialty tools do I need to do this myself. What I have and/or figured I need already:

Bushing puller that goes up to 1" (how much bigger will I need?)
Bushing/Seal driver set
Dial indicator
CK Perf. Pro Street and Drag Race Overhaul Kit
CK Perf. Transbrake valvebody
CK Perf. Rollerized steel billet clutch hub
Maybe a roller bearing from a TH350 for the rear?
Maybe a 4L60 teflon seal resizer?


Is that list good? What else should I get? I apologize for the ignorance. New to doing transmission internals.

 

[Tonimus]

@NickTransmissions Sorry for the bump, just wondering what your thoughts are.

 

[NickTransmissions]

@NickTransmissions Wonderful thread sir. I've had your rebuilding videos on while working at my desk to absorb some knowledge by osmosis.

I think I've learned enough to ask a less uneducated question. Long story short, the TH400 in my '78 burb needs a rebuild. Going to do a full drag race rebuild on it and toss it in my '78 Camaro. I currently have a 3500 stall converter and a Hughes TH350 35-1X which is good to 750hp, but I'm coming up on that soon. Additionally, I want to do a trans brake. The question is if I'm staying under 1k hp, what parts and specialty tools do I need to do this myself. What I have and/or figured I need already:

Bushing puller that goes up to 1" (how much bigger will I need?)
Bushing/Seal driver set
Dial indicator
CK Perf. Pro Street and Drag Race Overhaul Kit
CK Perf. Transbrake valvebody
CK Perf. Rollerized steel billet clutch hub
Maybe a roller bearing from a TH350 for the rear?
Maybe a 4L60 teflon seal resizer?


Is that list good? What else should I get? I apologize for the ignorance. New to doing transmission internals.

Id outsource the bushing R/R to a shop...Alternatively there is a dedicated Kent Moore branded bushing service set, J-21465-01 for TH400s available on eBay from time to time. It's not cheap but will allow you to r/r all the bushings. Get a Th350 pump bearing and a couple shims (.010, .015) for the rear to set up your rear end play. At 750HP, you'll need some hard parts beyond a billet forward clutch hub. Possibly one or both drums. You'll definitely want to run at least a 34-element HD sprag from a 4L80E which requires either a 4L80E direct drum or a 1964-1970 TH400 direct drum as both have smooth inner races designed for dog-bone style sprags. There's tons more; I'd suggest picking up at minimum the ATSG manual as well as Ron Sessions' TH400 book, if you can find it.

Not sure why you'd need a 4L60E teflon sealing ring sizing tool for a TH400. You will need a 4L80E center support teflon ring sizing tool (Kent Moore J-38736-7) as you'll want to be using teflon sealing rings on the pump and center support.