[455HOGT37]

I am going to build a TH-400 for the Cat, and I want this to be the last one it will need. I want to include the best features of all the years in one trans. The early trans had metal thrust washers and a sprag type clutch, but needs the center support machined for the late model case to support spacer. The late trans has the center support spacer but also has the undesirable roller clutch and plastic thrust washers. Aside from finding a '70 trans, which has all the "good stuff", is it better to find an early core and modify, or start with a late core and then have to find the sprag type clutch drum from an early trans? I have the capability to machine the center support and I will use roller thrust washers if that means anything.

Thanks

[455HOGT37]

I am going to build a TH-400 for the Cat, and I want this to be the last one it will need. I want to include the best features of all the years in one trans. The early trans had metal thrust washers and a sprag type clutch, but needs the center support machined for the late model case to support spacer. The late trans has the center support spacer but also has the undesirable roller clutch and plastic thrust washers. Aside from finding a '70 trans, which has all the "good stuff", is it better to find an early core and modify, or start with a late core and then have to find the sprag type clutch drum from an early trans? I have the capability to machine the center support and I will use roller thrust washers if that means anything.

Thanks

[455HOGT37]

Forgot to mention I was considering an Ultrabell, has anyone run one on a 400?

[Goatman]

Run an early one, they are the strongest. Most of my friends all run Ultra bells with no problems, but if the case is weak, the Ultra bell won't save it. Seen lots of cracked housings.

[455HOGT37]

I tend to agree with you on the early trans, but I have not done enough of these to know if the lack of the center support spacer ruins the case on a lot of them. I know this spacer is a "must" for any hi-po rebuild, but if your case is already shot because of dragging a station wagon around for 200,000 miles, you are screwed. The Ultrabell is only to is only a safety thing with me. I want to keep my feet, I have found them to be quite useful over the years. [img]/infopop/emoticons/icon_wink.gif[/img]

[PONTIAC DUDE]

The T-400's are all basically the same. But you will need to have a earlier sprag case(71 and earlier)to install the 34 tooth sprag in the later cases. I think that's what my tranny guy told me.

[Robert Williams]

The turbo-400 tranny case are all the same strength wise except GM did make a special beefed up 400 case that is strengthened with extra ribs. This heavy duty case was standard factory issue for Cadillac and 455 Super Duty applications.

[455HOGT37]

I guess what it comes down to is weather it is easier to find a good early case and cut the center support for the spacer or find a good early direct clutch drum for the late case. Damn, I used to have a half dozen 400 trans' lying around!

[TTS]

Hummm, A late (70'-87) 400 with the center support ring is the case to use. You can buy a late (4L80E) direct drum assembly new from the dealer and install it. Many, many mods. to consider- A Trans-go or preferably a Translab kit with the right frictions/ clearances/ tricks- you'll be good for 800-900Hp. An easy transmission can get VERY complex if you don't do them everyday.

[ April 04, 2002: Message edited by: TTS ]</p>

[455HOGT37]

So the 4L80 direct drum uses a sprag clutch? I have the 34 element sprag, a TCI overhaul kit and a Fairbanks manual valve body. I was planning on doing the clutch auto thing a few years ago so now I have all thse new parts lying around to do a "regular" strip trans. Oh yah, I have also read Ron Sessions book about a dozen times. I am ready!

[Half-Inch Stud]

Ahem, Let's cut through the Bull and get this one right:

Use the BIG CAR Pontiac Long-tail Case from 1969 to 1973. This case will feature 2-row internal ribbing at the rear-planetary location for case strength during those Dukes-Of-Hazard landings. Go for the 8-Bolt front-pump case.

Use the case that shows dramatically clear SANDCASTING finish rather than a DRAWN/FORGED exterior finish. The DRAWN/FORGED looking cases are known for cold-flow overlaps in the bellhousing and case body.

Use the Short-tail casting that features the extra external reinforment ribs. These tails ALSO contain the longer tail support bushing...for added driveshaft stability.

De-grease, file edges and Gray-prime and Machinery Gray-paint the case. Cover the identity tag during all operations with masking tape.

Use the 121 Front pump...next choice is the 895 pump. The 121 pump features added vacuum sensitivity within the Pressure regulator Valve...the ultimate Street/Strip TRANS-Attitude.

Use the 65-66 Rear Sprag Planetary if you are terribly anal about reliability...Truth is the Spring-Roller 1-2 Planetary does not fail. I consistently use the 65-69 Planetaries because I like the smooth exterior finish rather than the toothed machinework...but the lighter stuff is more efficient.

Use any 2-3 Planetary that matches the planetary and the Center Support. Be sure to pick a 2-3 planatary that has low exterior wear for decent Rear-Band friction...That's the life of your Reverse shift and ability to hold Reverse.

Re-Use the BIG CAR Torrington bearings. they are double-density Roller count. Compare the races with the any other single-density torringtons you may have laying around to reduce noise and friction from race texture.

Use the 69 and Newer Center-Support to take advantage of the Case-Saver C-ring. That Item is necessary in our usage. I really dug a 68 PC case up internally by chirping around in with a 68 Center Support. Was able to save that case by using the 69 Center-Support & Case-SAver C-ring.

You gotta use a super-stiff Rear-servo-Accumulator spring..usually Yellow...usually found in Chevy Truck and Olds 442 cars. I don't think I've ever found a Pontiac with the appropriate spring....embarrasing at the track to see folks chriping 1-2 manual upshift only because the TH400 applies REVERSE during the Manual 1-2. I can see the Rear tires go 0RPM for that instant around the 60foot mark. I can see the Driver's helmet lunge forward too. That's gotta be embarrasing for those reading this and realating. Fastest way into the low 13's if you're presently in the high thirteens.

Use the AH valvebody.
Use any separator plate, but you gotta drill 2 holes. You can use the 66-69 PC towing Package separator plate as-is...The VV GTO plate is crappy in comparison; gotta drill the two holes to bring it up to our standards.

You gotta remove a coupla checkballs.

ValveBody: Flip the 2-3 accumulator puck and toss the spring within the Valvebody.

Use a performance converter to avoid the Stripped-converter Sprag failure mode from the old GM donuts.

Use the best condition Forward Clutch Pack drum you can find. Look for wear in the Shaft-drum ring-sealing area. Oh, ah yes, there are some out there with low wear. USE the used Borg-Warner Radial-grooves clutches in the forward Clutch pack...if they are still red, I'm leary about certain versions of Raybestos. Gotto be non-flakey. Alto is too severe here. Waved-plate OK in here. I don't always use the waved-plate in build for my cars though. Makes for a solid Park-Reverse or Neutral-Drive shift....useless huh. Use 12 of the 16 springs for >500HP applications.

Use the least-burnt looking Direct clutch pack, and also features the smooth Sprag Race, so that you can upgrade it to the 34-element Sprag ($34 in 1990 prices). Use only new or darngoodused flat steels, try to use the thick steels. Do not use the waved steel. Use aluminum clutch piston with a ball-check. Use all 16springs.

Use Alto or possibly non-flakey Raybestos Intermediate clutches (only get 3), use only flat steels here. The Original Borg-Warner clutches are good too if you got them unburnt and can still read the inkstamps.

Use an intact,used, and only mildly burnt over-ride band.

1-2 Upshift Mod:
We already did it...drill a coupla larger holes in the separator plate, Yellow rear servo spring, good clutches and flat steels.

2-3 and 3-2 Shifts:
Remove the 3"approx seal from within the Direct Clutch Pack (Reverse and 2-3 chambers are now one big chamber). Remove the second ring seal from the Center-Support. Reverse and 2-3 feed are now able to feed both Direct pack chambers. Block the Center-Support's Reverse Feed hole (1/4" shaft from a cheap grinderstone is a slip-fit but block this hole by plugging the teeney-tiny feedhole in the Separatorplate. I use a nail-hammer-rivet method and sometimes use a tiny screw-nut peen-the-thread method on Sundays.

Use a Truck filter (screen instead of paper).
Use a small, Red-Striped, Adjustable Vacuum Modulator (for the sake of visually appearance)

Use a Gasket&Rubber kit, along with your new Direct and Intermediate Clutchs and steels.

Use a Govenor with the highest numerical inkstamp you can find. 11 is the worst, 13 is bad, 17 is good, 23 is great, 27 is small-cheby stuff.

Be real-good about the dipstick tube install and sealing...I leak these all the time. Go for the Bell housing mounted tube rather than the head-mounted tube...you'll thank me later.

Use 3/8 cooling lines and case fittings. the factory fittings are interesting because they are longer, and allow each Hex to be wrenched a tad easier. Real good idea to relocate the engine oil filter to the passenger wheel-well in my opinion.

I use a stock Turbo-Hydramatic pan. Was real bored with the deep pans and sold them both away.
I run a PSI gauge on my Steering column...still waiting to see a pressure dive at the big end.

Run a BIG CAR yoke....on the 12-bolt Rear. This keeps us Poncho folks running the preferred U-Joints while cheby folks run some small U-thingy.

Fill TH400 on level ground. until fluid runs out of Modulator hole. Dipstick is useless in my carcare habit.

Have a nice day,

H.I. Stud

[455HOGT37]

Thanks Stud, for your time on that post. An unexpected wealth of information from everyone, thank you. [img]/infopop/emoticons/icon_smile.gif[/img]

[Half-Inch Stud]

You're very welcome...OPH would be proud. [img]/infopop/emoticons/icon_wink.gif[/img]

H.I.

[TTS]

Oh well, I may as well add some things. First, remember a transmission will respond differently to different torque inputs. 1) Don't see the need in seeking out a pump- grind a flat on the PR valve @ the 3RD land from the spring flush with the groove and we'll have good converter feed/ lube. Pump capacity is equal across the board. I am not saying that pumps are equal, only that the capacity to charge is equal- NO problems.
2)Reverse will NOT apply during the 1/2 shift reguardless of what 1/2 acc. spring is used. What is happening, is the Direct clutch (Hi, 3RD. whatever you call it) is applying centrifically-sp? while the reverse, also used in man. 1- along with the Direct clutch, band is not unapplied yet (reverse or more accuratly a brake). By adding a stronger spring @ the 1/2 accumulator we will not solve the direct apply but eliminate the band at the time when direct is applied (1-3-2). The correct solution is to add to the direct clutch return spring pack eliminating it from applying during a 1/2 shift- and maybe an oil bleed here and there [img]/infopop/emoticons/icon_wink.gif[/img] .
3) The only checkballs truly needed are the front center and rear center (2). Although depending upon application more in the right places are needed, as long as autocross isn't on the menu [img]/infopop/emoticons/icon_smile.gif[/img] .
4) Use the late case as I described in the earier post, the early stuff is fine but tough to get a center support ring installed - The weakest link. A 4L80E Direct drum does work, same as the old one (pre-70). The low roller as described previously has no real problems. Use a 200C center support seal @ the passenger side center support oriface in the worm track, block the driverside oriface and leave the second sealing ring off of the center support for more apply area as stated above.
5) It is too complicated to get into the modulator valve mods. that are benificial, but not absolutly needed.
6) Ok, might have given more away than I should have [img]/infopop/emoticons/icon_smile.gif[/img] . Endplay- something a Pontiac man should know about. Simple, keep the rear unit less than the front - I like .001" or so with .003" or so!
7) Use any filter as long as you maintain it. An Allison filter is just a screen, no prob. just maintain it.
8) A dual red stripe modulator will provide the fastest line rise although not always needed.
There you go, I am sure I left out some things- some by accident, but I have done this a few times [img]/infopop/emoticons/icon_smile.gif[/img] and deserve to leave out the specifics!

[TTS]

[ April 08, 2002: Message edited by: TTS ]</p>

[455HOGT37]

Thanks for giving away a few trade secrets, TTS. [img]/infopop/emoticons/icon_wink.gif[/img]

[Half-Inch Stud]

TTS,

Agreed on the Front Pump volumes as same. Agreed on filing a flat on the Pump regulator..I'm that lazy though to seek out the prefered pump& matched Regulator. However, I still think the PUMP Regulator that features the 4 small holes is more sensitive to Manifold-Modulator Vacuum signals, thus provides a more Dynamic Line Pressure during WOT versus highway cruise versus Downhill.

Agree on the checkball philosophy.
Interesting about the Drum interchanges...just not gonna crack 200C and 4L80E cases for common TH400 parts....unless they become uncommon in these parts..

I always optimize endplay for about .020"
I always optimize forplay for about .020" or .02hr depending on the situation.

We should/could talk. I'm not in the trans/TH400 business.

H.I. Stud