TH400 build
July 29th, 2018, 10:28 AM
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TH400 build
Building a TH400 and have a couple of questions for any trans experts. My build is mild 455 430hp 530ft torque. 3:91 gear but may change to a 3:23 later I upgraded to a 34 element sprag 4L80 direct drum. It was set up with 5 frictions and 4 0.092" steels and one wav steel. My 400 input drum had 5 frictions and 5 .080" steels no wav. I know the OW W30 trans had no wav plates at all (except fwd drum) and 6 frictions in the direct. My dilemma is whether to go with 5 frictions and thicker steels or 6 frictions and 0.077 steels. Obviously GM went to only using 5 frictions and thicker steels in the 4l80. I know thicker steels give better heat dissipation. What are the benefits of 6 frictions over the 5? Also I'm getting a lot of mixed opinions on whether to use wav plates in the direct and intermediate pack. I know that no wav's means firmer shifts and is better on the frictions and steels due to less slip. I will be using a custom 2600 or 2800 converter which will add to cushioning the shift.
July 31st, 2018, 03:05 PM
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I don’t use any waved plates in my builds. Rule of thumb is to maintain .010-.015 per clutch clearance. Dont use the stamped steel pistons, if you can’t find aluminum pistons use the 4L80 direct clutch bonded pistons and spring retainer. You may have to stack a couple old steel plates in the bottom of the clutch pack to take up some clearance using the 4L80 pistons.
August 1st, 2018, 12:25 AM
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Thanks Matt,
I've found everything I need and have it figured out. Just need to decide if I want to go with 6 or 5 frictions in the direct. Have all aluminum pistons and no wav's except in the forward drum.
I've found everything I need and have it figured out. Just need to decide if I want to go with 6 or 5 frictions in the direct. Have all aluminum pistons and no wav's except in the forward drum.
August 1st, 2018, 01:10 AM
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I prefer smooth clutches in the forward clutch, it isn’t a shifting clutch pack. Might as well build it with as much surface area as possible. You need to run some kind of grooved clutch in the directs, either a waffle or radial friction. The idea of the grooves is to allow the fluid that gets in between the discs an escape path. It’s also a good idea to drill a exhaust hole in the drum to allow trapped oil an exhaust path. The direct drum turns almost as fast as the input shaft, the small amount of oil that isn’t released can climb the edge of the drum and put just enough pressure on the piston to drag the clutch. An added benefit is the oil that does escape will lube and cool the sprag. Measure .415” from the outer diameter of the drum, and drill a 1/16 hole from the sprag side of the drum. Install all 16 springs, once again this helps the clutch from centrifugally applying at high rpm.
On my high horsepower/high rpm builds I use smooth clutch discs on the intermediate clutch, the oil caught between the discs help cushion the clutch apply and help keep the sprag from rolling and leaving you with no 2Nd gear. If you use 4L80 thin steel plates and a early 4L80 intermediate backing plate you can use 4 frictions in place of the factory 3 on the 400.
On my high horsepower/high rpm builds I use smooth clutch discs on the intermediate clutch, the oil caught between the discs help cushion the clutch apply and help keep the sprag from rolling and leaving you with no 2Nd gear. If you use 4L80 thin steel plates and a early 4L80 intermediate backing plate you can use 4 frictions in place of the factory 3 on the 400.
August 1st, 2018, 10:04 AM
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Yeah I know about the hole to prevent centrifical apply. Have HD springs for direct and was planning on adding a full compliment of springs on the intermediate as well. This car will be mainly street driven with some time on the track. It's not really intended to be a race car. Should be around 400 to 500hp max and 530ft torque. Haven't dyno'd yet, but will be soon. Also will be dual feeding internally as well. The way this thing was set up before it was slamming into 2nd so hard it would break both tires loose shifting to 2nd with a 250hp 350 anything above 1/4 throttle. That's not what I want, comfortable shifts up to 1/2 or 3/4 throttle and firm crisp shifts at wot. Trans had only two check ***** in the valve body. I'm guessing that's why it slammed so hard. I didn't find anything else done to accum's or valve body. I was expecting to find the pump spring shimmed, but even that was left alone. There was also a hole drilled in the direct drum just above the top of the piston below the first steel. I'm thinking it was to help exhaust fluid from the drum during apply? I'm putting 6 check ***** back in. I should mention too that engine won't see much spinning above 6K. Using a 2800 converter. 3;91 gear though I might change to a 3.23 later. I rollerized the rear thrust too.
Sounds like you've done a few 400's, this is my first 400 (done a couple of 700's and 4L60e's). What are your thoughts on getting the shifting I'm looking for with this set up? I was going to leave the separator plate alone for now, but if it seems it needs further firming up then I'd drill the 1-2 feed to 0.110 and or 2-3 to 0.125
Sounds like you've done a few 400's, this is my first 400 (done a couple of 700's and 4L60e's). What are your thoughts on getting the shifting I'm looking for with this set up? I was going to leave the separator plate alone for now, but if it seems it needs further firming up then I'd drill the 1-2 feed to 0.110 and or 2-3 to 0.125
Last edited by cman442; August 1st, 2018 at 10:13 AM.
August 1st, 2018, 10:11 AM
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I'm trying to decide on 5 frictions and 0.90 steels or 6 frictions and .080 steels in the direct. I can set it up either way. I was going with waffle Hi energy in the intermediate and direct and smooth tans in the fwd. It had waffle's in the fwd and intermediate and smooth in the direct. Completely opposite from what I would have done. Only thing I'll say is the trans was in great shape. You could still read Raybestos and the part numbers on the clutches. I almost thought about reusing some of them, but didn't feel comfortable using 30 year old used frictions for it costs to replace them.
August 1st, 2018, 11:36 AM
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I drill the 2nd and 3rd clutch feed holes to 3/16, 2 checkballs, block the 2-3 accumulator feed in the valve body, either the yellow or 4L80 orange 1-2 accumulator spring. I guess I need to mention I build them this way if I know the owner has a loose converter, I’m pretty sure it would knock the dash out of the car with a stock tight converter. If the converter is stock I’m much more conservative with feed hole size, you can make the bigger much easier than smaller! There are also some changes you can make to the accumulator valvetrain to take out some of the low speed bang-screech shift
August 3rd, 2018, 09:23 AM
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Clutches came today. I couldn't find a source for the Borg Warner Hi-energy that most seem to recommend. I went with the Raybestos hi-engergy but the are a grey graphite color. Any experience with these?
August 3rd, 2018, 06:54 PM
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T Borg/Warner high energy forward clutches are kinda gray. Once they have some fluid soaked in the look slmost like a olive green. The clutch part number in the TransStar catalog is 34106HD for the waffle (direct clutch) 34104HD (intermediate waffle) and 34106 for the smooth forward clutch. These are Borg/Warner frictions, this catalog doesn’t have part numbers for Raybestos.
August 3rd, 2018, 08:03 PM
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Weird thing is when you punch those part numbers into google you get suppliers selling Raybestos not BW. I haven't tried calling transstar direct, but local builder that's retired said they most likely won't sell to you unless you have an account. The frictions that were in the trans were tan waffle. I'm just worried because my local guy said stay away from the pricey race frictions green and blue because while they hold up well they make a lot of debris and will likely clog the filter quickly. Ok for a race car only driven on track, but not good for street driven car.
August 4th, 2018, 05:20 PM
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Weird thing is when you punch those part numbers into google you get suppliers selling Raybestos not BW. I haven't tried calling transstar direct, but local builder that's retired said they most likely won't sell to you unless you have an account. The frictions that were in the trans were tan waffle. I'm just worried because my local guy said stay away from the pricey race frictions green and blue because while they hold up well they make a lot of debris and will likely clog the filter quickly. Ok for a race car only driven on track, but not good for street driven car.
the blue clutches are are designed for extreme heat, think like off road trucks or cars that leave the starting line on the rear bumper. The handle the slight slippage of momentary loss of fluid if the filter gets uncovered. I wouldn’t pay a dime extra for the kolene steels. Why would you need a extra hard surface on a steel plate?! A standard steel is much harder than any friction, that any they tend to darken the friction plate.
August 4th, 2018, 05:57 PM
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These were just Hi energy's graphite color instead of tan. I know the ones in my trans are from 1990's so sure things have changed. They were tan waffle. My new ones are graphite waffle. Looks like the standard smooth frictions are tan color.Yeah heard koleens are a waste of $$ I've actually decided on 5 clutches in the direct with 0.092 steels instead of the 6 clutches with 0.082 steels. Seems consensus is 5 are enough for my power range and thicker steels are probably better.
August 7th, 2018, 09:11 AM
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Five clutches with 180-200 psi of line pressure will hold 700-800 easy. Dual feeding the directs Is big help. I have asked many knowledgeable people, nobody can give me a good explanation of why Hydromatic decided on the added complicity’s of the direct clutch with 2 separate hydraulic circuits for reverse, and only one for direct. Seems like a lot of added expense and needless engineering.
August 7th, 2018, 09:12 PM
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Speaking of that, it seems to me that you could either dual feed by leaving out the seal on the direct drum, seal between dir and rev on the center support to dual feed. I know they tell you to do both, but really just one is needed. If you leave out the seal on the drum separating piston fill cavities, then direct pressure fluid would fill both cavities of the piston. If you left the seal in on the drum and left the seal out on the center support then same thing, fluid would crossover from the direct to the rev and fill both piston cavities. Same on plugging the reverse feed plug. You can plug it at the center support, case, or separator plate. The trans go kit does both though the 3 piece separator plate. Guess it's a matter of builder preference. I would think plugging at the center support would be best that way no accumulation effect filling although way back to case through the reverse feed. Although guessing not much to be gained.
What's your flavor on this?
What's your flavor on this?
August 8th, 2018, 04:20 AM
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I prefer to close the hole in the spacer plate. My second preferred methode is to block the hole in the case with a freeze plug.
I omit the center seal in the direct drum, and leave off the seal on the center support. Some people machine the second dealing ring grooves in an attempt to eliminate any glow restrictions. Anything to speed the flow of oil. I don’t know how much of an improvement the machining makes. I doubt it would hurt, but I doubt your “butt-o-meter” would be able to tell.
I omit the center seal in the direct drum, and leave off the seal on the center support. Some people machine the second dealing ring grooves in an attempt to eliminate any glow restrictions. Anything to speed the flow of oil. I don’t know how much of an improvement the machining makes. I doubt it would hurt, but I doubt your “butt-o-meter” would be able to tell.
August 14th, 2018, 04:07 AM
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I have never tried one, so I can’t say much about them. All I have ever used is good used or factory relined bands. If the band isn’t slipping with standard friction material I don’t see a need for a fancy upgrade. If it ain’t broke, don’t fix it!!
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