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#1
05-04-2000, 07:01 PM
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I'm putting together a TH-400 for use with a Switch-Pitch converter(rated 1400 low/4000 high stall) I think the motor is around 425-450 HP and I may build a stronger motor in the future. I have a TransGo 400-2 Reprograming Kit and will be installing a HD sprag. I plan to follow the instructions provided with the TransGo kit(and factory service manual) but would like suggestions about any other modifications or parts substitutions I should make when building the trans. I have a complete O/H kit(frictions and steels) and I have 3 different TH-400s to use as cores. One is a 65, one is a 70 and one is a 77(I think) I cannot use the 65 case(fits Buick "Nailhead" only, anyone need one of these cases?)and the band surface on the reaction carrier is scored but all other internals inc. the valve body are good. All parts in the 70 trans. inc. case are good and the 77 trans is complete. I have not torn it down but it is supposed to be a fresh rebuild. Is the valve body in any of these trans. superior to the others? Any other parts that are superior or that I should modify? I think I have all of the trans parts and the converter has been shipped so I hope to put the trans together over the weekend. Your suggestions/comments would be appreciated.**********Thanks, Joel
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#2
05-04-2000, 07:01 PM
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I'm putting together a TH-400 for use with a Switch-Pitch converter(rated 1400 low/4000 high stall) I think the motor is around 425-450 HP and I may build a stronger motor in the future. I have a TransGo 400-2 Reprograming Kit and will be installing a HD sprag. I plan to follow the instructions provided with the TransGo kit(and factory service manual) but would like suggestions about any other modifications or parts substitutions I should make when building the trans. I have a complete O/H kit(frictions and steels) and I have 3 different TH-400s to use as cores. One is a 65, one is a 70 and one is a 77(I think) I cannot use the 65 case(fits Buick "Nailhead" only, anyone need one of these cases?)and the band surface on the reaction carrier is scored but all other internals inc. the valve body are good. All parts in the 70 trans. inc. case are good and the 77 trans is complete. I have not torn it down but it is supposed to be a fresh rebuild. Is the valve body in any of these trans. superior to the others? Any other parts that are superior or that I should modify? I think I have all of the trans parts and the converter has been shipped so I hope to put the trans together over the weekend. Your suggestions/comments would be appreciated.**********Thanks, Joel
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#3
05-04-2000, 10:07 PM
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Joel, go for the '70 case and make sure you keep an eye on all the rear gear assemblies. Some of the spline sizes changed in the sun gear assembly in the 60s and 70s. Use the good frictions (BW or Raybestos) and presoak them in ATF. Follow the instruction in the kit and all will be good. Drop me a note at thand@sprintmail.com and I can tell you the other sizes to consider for the plate holes.
Tom Hand
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Tom Hand |
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#4
05-05-2000, 08:15 AM
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i'd pull the one way roller clutch out of the 77 and install it instead of the sprag. the sprags had a bad habit of flipping over center in high horse applications,rendering them inoperable. unless the new one that you ordered has been modified to eliminate this problem. this is personal opinion,and also the reason that gm went away from the sprag unit in 71. mike
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so many pontiacs, so little time.................. moderator is a glorified word for an unappreciated prick.................. "Only two things are infinite, the universe and human stupidity, and I'm not sure about the former." --Albert Einstein "There is no such thing as a good tax." "We contend that for a nation to tax itself into prosperity is like a man standing in a bucket and trying to lift himself up by the handle." - Winston Churchill |
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#5
05-06-2000, 10:46 PM
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I'm guilty of building one of these trans then letting it sit complete on the bench so far.
The '70 is probably the best all around starting point from my limited knowledge. A 472 Cad or 455 Olds in '70 will have a 6-friction direct clutch that accepts the sprag type second gear one way clutch. If the second gear sprag has dog-bone elements with flats worn on them or if the spring elements are weak you can replace it with another good stock one or a 34 element aftermarket unit (which I did). I think I heard somewhere the new 34's are softer than the factory 16's but 34 elements provide more even loading against the outer race which is a benefit anyway. Plain factory type frictions - new or good used - seem to be recommended by Ron Sessions in his book and by some other builders on this BBS. Not all cases in the 70's had the passages to operate the V/P although the 455 big car cases had the passage at least until '76. Some folks like John Kilgore supply a slightly modified front pump that works even without the passage anyway. Stock valve bodies from older heavier vehicles probably provide the firmest shifts but the TransGo will probably allow you to tune any of them up anyway. I lucked out and got a motor home valve body that will be firm enough stock since it's from a 13,500 lb vehicle. Watch the steels for clearance against the ID of the hubs. Some of my new ones wouldn't slide freely so I reused some good used ones instead to make sure the stack could apply and release freely. Tom Hand will be a big help on more advanced topics or fine details. Mike ------------------ |
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#6
05-06-2000, 11:14 PM
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Mike, thanks for the information as usual. By the way, were those Alto steels that have had interference? Those are the ones I have been having trouble with. They need to sharpen their cutters I think!
Tom Hand
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Tom Hand |
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#7
05-08-2000, 10:23 PM
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Tom,
You're welcome. Just went out and looked at the remnants of my rebuild kit and some of the steels do say "ALTO USA" out on the lugs. The kit was purchased in January 1999 from Recon A/T in Pittsburgh. Mike |
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#8
05-09-2000, 03:37 PM
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I want to pass on some information and tips I received from an experienced, professional builder of 400s and other transmissions.
"Alto steels have been presenting a problem lately but they work IF they fit. However, it is a nightmare to make them fit properly. Allomatic steels are a good choice. Alto friction (clutches) (RED) have consistently been the best in our performance applications, or any application you don't mind the quicker shift. We also like Borg/Warner H/E frictions, then regular "tan" Borg Warners. Raybestos clutches do not seem to have worked as well for us as the others; not even the "Blue Plate" frictions. Allomatic frictions are not what we would use in performance applications. Hope this helps!" Thank you for the tips, I am sure it will help. Tom Hand
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Tom Hand |
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