[TRADERMIKE 2012]

Mike here: You nailed the diagnostic on the head, the seals are metal clasp type in the forward drum between the back of the Stator and in the front drum area, one was broken in half and the other was unclasped!

[TRADERMIKE 2012]

Originally Posted by Half-Inch Stud

Sounds like the clutch pack didn't get the lipseals refreshed, or/and was driving around Low-on-Fluid and schortched the FWD Pack. Clogged Fabric filter.
This is a 10-foot pole drama of errors to me, so don't want to get involved: too far away for eyes-on guidance. Aside from that:

Replace the Front Pump, Converter because something got whacked badly. Take high impact to crack-out a Converter Neck fracture. Front Pump bushing-bore took the force.
Visual inspection of bushing wear, parts wear is the big deal for the TH400, all rebuilds.

FWD drum: look for scoring inside the 2-seal ring contact area and shaft wear there.
DIR Pack: needful to perform the Mid-Seal removal, Center-support 2nd ring removal, and Reverse-Bleed tiny-hole plugging in Separator plate. <-- a modification for nice 2-3, 3-2.

Valvebody: Flip the 2-3 Puck, toss the big valvespring, puck immoble in VB (some pucks may have 3-tabs to gring down)

use only 3 checkballs: they are nearly in a straignt line in the Case.

In conclusion; Good luck, and donta want to get involved beyond the above-typed internet advice. HIS

"Replace the Front Pump, Converter because something got whacked badly. Take high impact to crack-out a Converter Neck fracture. Front Pump bushing-bore took the force.
Visual inspection of bushing wear, parts wear is the big deal for the TH400, all rebuilds."

Mikes reply: I had to replace the Torque Converter and the pump as well, good advice, thank you, long past due.

[TRADERMIKE 2012]

Originally Posted by Schurkey

The TH400 is "THE" easiest-to-rebuild-as-a-DIY-project 3-speed transmission. All the gears in the back, all the clutches in the front, no pistons in the case. A danged fine unit; similar to but more sophisticated than the Mopar 727 because in "Drive" the 400 never has to release a friction (band or clutch) to engage the next gear--it just adds another clutch on the upshift. Therefore, shift timing is easier.

1. I really liked the B&M rebuild instructions when I did my first 400 about a thousand years ago. Still have a photocopy of them in The Library downstairs. They make a big deal out of drilling various holes in the hard-parts "oversize"; when I've checked the 400s I've gone through, all those holes were already at the sizes specified. APPARENTLY, drilling those holes applies only to very early 400s. Mind you, I've got little use for B&M shift kits, but the rebuild instructions are excellent in terms of pictures and simplicity. They don't cover bushing replacement and other, more-in-depth items. And when it comes to shift kits, I'll take TransGo, thank you very much.

2. Bushings are a great idea...if you can install them properly. If you can't push 'em in correctly, you're better-off with the originals if they're in usable condition. Of course, any bushing that's obviously worn-out or damaged has to "go".

3. Not a big fan of the plastic thrust washers. Yeah, lots transmissions have them and they work just fine. Given a choice, I'd replace 'em.

4. Far as I know, rear end-play and front end play are the only end-play measurements to be concerned about. If there's more than that, I don't know about 'em. (That does not include "clutch clearances" of course.)

5. I've heard really good things about the 4L80E pistons with molded-on seals. Never use 'em personally. About the same with the solid Teflon sealing rings. I used the metal rings with the hook ends; I've used Teflon scarf-cut seals, (Put the scarf-cut seals on properly!) but "I'm told" the solid Teflon rings are the way to go...if you have the expander tools and the re-sizer tools; and virtually nobody in a D-I-Y capacity will have that.

6. There's "special tools" to select the proper pin-length for the band apply pins. Again, "good luck". Everyone I know just re-uses whatever pin came out of the transmission.

7. Get the center support properly loaded, and the bolt torqued to spec. I keep a socket JUST for that use, so that I don't wear out the socket points on other fasteners, and then wreck the wrenching surface of the center-support bolt. Most folks wouldn't bother with that. What I'm saying is "don't use a worn-out socket" on that bolt. This is a lesson I learned from 12-point Honda cylinder head bolts; if the socket isn't PERFECT, "good luck" getting the head bolts out without tearing up the wrenching surface, or rounding them off. Look for case wear from the center support moving around.

8. I put two lubricated O-rings on the filter tube where it shoves into the pump; and two lubricated O-rings on the modulator where it goes into the case.

9. Verify Governor operation, and tune the governor as needed to get the shift points where you want them. Don't dick with the modulator to tune the shift points, at least not excessively. If the original, huge, black OEM modulator isn't defective, I use that in preference to the small, compact, inexpensive aftermarket modulators. The OEM modulators are altitude-compensated (barometric pressure compensated).

10. MAKE SURE THE TRANS COOLER TUBES ARE NOT RESTRICTED, AND THE TRANS COOLER(S) ARE CLEAN AND NOT RESTRICTED. Given a choice, I'll use 3/8 cooler tubes instead of the more-common 5/16 tubes. Flush the cooler(s) to get debris out. If they're too bad, they'll have to be replaced. Restrictions in the cooler circuit can destroy the crankshaft thrust bearing/crank thrust surface. Some guys restrict the fluid passage into the converter to prevent over-pressurizing the converter leading to thrust problems; I don't know that that would be needed in your situation. Have a local trans shop flush a used torque converter, too. But I suppose you'll have a new or rebuilt converter for your assembly.

11. The TH400 world seems to revolve around the 34-element sprag clutch on the Direct drum. That's what I've used when I can get a suitable drum to use it with. HOWEVER, I have heard that the roller-clutch is just as good, and way cheaper. This is not something I've experimented with. If other folks tell you that the roller clutch is a troublemaker, I suppose you should believe them. IF you use a sprag clutch, or IF you're buying a core direct drum from some unknown transmission, MAKE SURE THE SPRAG/ROLLER CLUTCH SPINS THE PROPER DIRECTION. The rear-wheel-drive versions of the 400 (375, 400, 475) spin the clutch one direction, the front-wheel-drive TH425 has an identical drum generally with the extra clutch plate inside; but the clutch spins the opposite direction. DO NOT SCREW THIS UP.

12. Consider the ATSG manual, the Cliff Ruggles TH400 rebuild/modification book, and--if you can find it at a reasonable price--the out-of-print Ron Sessions TH400 rebuild/modification book.

1)Mikes reply: I reused the B+M shift kit plate and Balls exactly since it was drilled, with new gaskets, that came with the rebuild kit from B+M also.

2)I bought a new Bushing driver kit for this rebuild and learned how to Bush the Bushings upon Installation. A good blow on the hammer to set the Bushing, using a larger disc and steady blows thereafter, until you can't go anymore. Then use a smaller disc inside driving just below the champhord edge or beveled edge, to seat the Bushing properly. On the Bushings that are to be bottomed out, drive until you hear that metal-to-metal sound, only. Then to Bush the Bushing, one could use a mating shaft through that Bushing, by tapping a hammer (on a suitable area) above and below the Bushing to be reformed, to resize a deformed Bushing installation.

3) I used Torrington Bearing s in 4 places, rear of the case and 3 places past the center support.

4)There is front and rear end play and then there are the 3 clutch pack Tolerances. Then above what the factory talks about is the rear Bands effect on the Sun, Ring and Planetary gear housing, that can be shimmed for less play when in use. In addition, you can reduce the end play and rollerize and shim the main shaft to rear ring gear area at the rear of the gears. Note, there are sites that explain this deeper than this explanation, even though I used these procedures when I built my Trans, I can't explain it better without reading through my notes at this time, sorry. I hope you got the Idea. Racers make these mods.

5) I also used the Metal clasp type seal rings as the factory used in those days. My Pistons at each clutch pack used the lip seals that are added to the piston, my reading likes them better than the latter ones that had the rubber added to the pistons. The large Accumulator/Servo used a rubber ring on the large piston though.

6) Sonnox makes a Pin kit for the Accumulators/Servo that are adjustable, so you start off with new settings that can be shimmed in the future with washers supplied in the kit. I used these kits and the Pressure Regulator /Boost Valve kit too.

7) The Center support was in good shape and the Case Lugs were not damaged as well. I used the Metal clasp rings on all 4 areas and the socket I had was in unused condition.

8) I put two lubricated O-rings on the filter tube where it shoves into the pump; and two lubricated O-rings on the modulator where it goes into the case, as you said.

9) Verify Governor operation, and tune the governor as needed to get the shift points where you want them. Don't dick with the modulator to tune the shift points, at least not excessively.

Mikes reply: I can't do this until I get past the shifting problem, I am experiencing. Also, my can type Modulator is tossed.

10) We blew out the Radiator and secondary cooler and I purchased a new Torque Converter from Hughes and it works well. I plan on buying the Metal 3/8 lines after I break in the Trans. rebuild and fix my current shift problem.

11) Lucky for me this 1967 TH 400 PC code Trans. came from the factory with sprag clutch on the Direct drum and roller-clutch at the front gear.

"MAKE SURE THE SPRAG/ROLLER CLUTCH SPINS THE PROPER DIRECTION."
Mikes reply: We checked the rotation as we built the Trans.

12) ATSG manual was used to build this Trans. as well as the 1967 service manual in conjunction with Internet documents and many online videos. Plus, online forums such as PY forum.

[TRADERMIKE 2012]

Mikes reply: I would like to add my other site for you to reference after reading this post.

SEE: 1967 TH 400 "Fresh rebuild", Problem in shifting!

[TRADERMIKE 2012]

Mike here to continue my Trans. rebuild and any discussion that has to do with "The Pontiac Experience", say anything here and all are welcome. The unwritten law on "how long a Thread should be" is now established by the modulator and we will keep it to 800 this time. Fair enough let's continue...

Lou and I are taking Pressure readings on a TH 400 Trans. That we successfully completed recently, although other problems were raised, before we could test and tune the rebuilt Trans.

SEE: "Question about 041 Cam", this is where you can pick up the former conversations on this PY forum and learn a lot from those who know best, I am just your narrator for the duration and am learning as I go.

This is the following results of our recent test while garaged:

"Vacuum hose is connected to the vacuum Modulator".

By the book PSI/ DATE
Closed Throttle/ 12/6/23
@ 1200 rpm./ Trans. Repaired/ Trans. Broken

Drive 70/ 110/ 90-110

Neutral 70/ 150/ 110

Park 70/ 100/ 95-120

Second 150/ 200/ 90

Low first 150/ 200/ 90

Reverse 107/ 210/ 100-125


Note: I think I got this Info. From a Tempest Service Manual?

Note: We think that the higher pressure than the book is because we installed a sonnex pressure regulator upgrade in the pump, it has "o" - rings to seal, while raising the pressure gradually as the rpm's increases.

"This next Test is done with the Vacuum modulator disconnected", In the garage.

Zero output speed @ 1200 rpm.
By the book/ Rebuilt Trans.
Drive 150/ 110

Neutral 150/ 150

Park 150/ 150

Second 150/ 190

Low first 150/ 190

Reverse 244/ 250



Mike wants to know what "Cliff" thinks about these numbers, so far?

The road test is coming tomorrow, if all goes correctly. We let the vehicle down off the blocks and hope there are no problems with underload conditions when we actually drive the vehicle on the highway.



Lou found these numbers in a book, most likely the 1967 Pontiac Manual.


Vacuum disconnected/ Vacuum connected
by the book/ by the book
Drive 70/ 150

Neutral 70/ 150

Park 70/ 150

Second 150/ 150

First 150/ 150

Reverse 265/ 244

[Half-Inch Stud]

Looks to me from the Before/After PSI readings; the Center-Support Babbit Bushing was clapped-out, and replaced.

[Schurkey]

Originally Posted by TRADERMIKE 2012

Lou found these numbers in a book, most likely the 1967 Pontiac Manual.


Vacuum disconnected/ Vacuum connected
by the book/ by the book
Drive 70/ 150

Neutral 70/ 150

Park 70/ 150

Second 150/ 150

First 150/ 150

Reverse 265/ 244

Schurkey wonders why the pressures are lower when the vacuum modulator is not supplied with vacuum. The pressure is higher with vacuum???

[Dragncar]

Maybe we could all go "third person" and make this really all weird ?
Myself, I would recommend not rebuilding anything.
That way no one can over think it all and make simple things super complicated.
T400s are very tough, plenty full and cheap. Hard to screw one up.
Just get a Sessions book and be done with it.

[Half-Inch Stud]

HIS figures the text and readings just gottabe swapped.

[Schurkey]

Originally Posted by Half-Inch Stud

HIS figures the text and readings just gottabe swapped.

Schurkey suspected as much, but was looking for confirmation...and to make a point.

[vertigto]

Y'all are hilarious.

Vertigto always thought this thread/style was particularly odd...glad I'm not the only one.

[dataway]

Oh, believe me, you're not the only one, dataway thinks so too.

Although, I think Yoda is on board with it.

[Formulas]

Formulas mom here.... Its ok to snicker Its impolite to point and laugh..

[Gach]

Oh my god this is hilarious the blind leading the blind. Wait got clean my glasses. Oh now I see. LOL

[Half-Inch Stud]

OMG, Gach made sentences with proper spelling. it's not Gach. Need a "too", a "can", and a commas. Still not Gach.

[Schurkey]

Schurkey is amused.

Feeling somewhat guilty, but amused nonetheless.

[Half-Inch Stud]

So, how does the TH400 do while driving? HIS wants to know.

[TRADERMIKE 2012]

Mike made a mistake on post #45, correction below



"Vacuum Disconnected", @ 1200 RPM, Rebuilt Trans. Pressure readings.

By the Book PSI/ Test result PSI

Drive 70/ 110

Neutral 70/ 150

Park 70/ 150

Second 150/ 190

First 150/ 190

Reverse 265/ 250

Repaired above is to post #45 "Vacuum Disconnected."



"Vacuum connected" below, @ 1200 RPM, Rebuilt Trans. Pressure readings.


By the Book PSI/ Test # 1, result PSI/ 12/11/23 Test # 2, result PSI

Drive 150/ 110/ 120

Neutral 150/ 150/ 150

Park 150/ 100/ 150

Second 150/ 200/ 150

First 150/ 200/ 150

Reverse 244/ 210/ 230

[TRADERMIKE 2012]

Originally Posted by Half-Inch Stud

So, how does the TH400 do while driving? HIS wants to know.

Mikes reply:

Thank you for asking, we had the hose from the Trans. out, Barb fitting to the Pressure Gauge, get burned by the Header and lost some fluid and smoked like hell. We re-routed the Hose and wrapped it in Header cloth and inserted a metal shield under the collector where it meets the exhaust pipe and ran the hose under that, so as long as the hose were using can take at least 300 psi, we should get our "on the road test" readings by this weekend or sooner? We secured the hose to the frame this time using a mount, with some slack, in order "not to pinch" the hose either. The hose and Gauge come up to the driver's side mirror and is long enough to reach the passenger, who will record the test readings while were underway. The type of Tests that we do will be from what we wrote down on paper that we will take with us on the road.

[Dragncar]

None of that matters. Trans Go shift kit after a basic rebuild with basic modifications and run that B!&h !
Is this transmission even doing anything wrong ? Rebuilt several, never a issue except for drinking a few beers while installing front pump and broke a ring. Caused some damage due to me, not the wonderfully designed Turbo Hydromatic 400 !
If you have a good pump, seals/bushings are OK and the clutch/steel clearances are right these things work and can take a beating.
Its the people who screw them up. Or just overthink their own problems that do not exist in reality and chase their tails.