[SaM91]

Hello! I'm from Russia. I have Toyota Supra with 2JZ-GTE engine 1250 HP and TH400 transmission. It has manual shift valve body, transbreak. It was build in Coan last year, then I had rebuilded it several times. Now I have a problem - direct clutch pack often burns out. It has all Alto Red Eagle clutches. What can be the problem?

[cobalt327]

Originally Posted by SaM91

Hello! I'm from Russia. I have Toyota Supra with 2JZ-GTE engine 1250 HP and TH400 transmission. It has manual shift valve body, transbreak. It was build in Coan last year, then I had rebuilded it several times. Now I have a problem - direct clutch pack often burns out. It has all Alto Red Eagle clutches. What can be the problem?

Have you checked the line pressure?

Have you had the dual feed mods done to increase the apply area of the direct clutches? It is described by Jakeshoe, beginning about 2/3 of the way down the page here.

How many frictions and steels are you using? Do you know the clearance it was set up with?

On a side note, do not put the tranny into neutral after a pass, this can overspeed the drum and scatter it and the case, etc. Don't do your burnout in low, start in second.

[Crosley]

Originally Posted by SaM91

Hello! I'm from Russia. I have Toyota Supra with 2JZ-GTE engine 1250 HP and TH400 transmission. It has manual shift valve body, transbreak. It was build in Coan last year, then I had rebuilded it several times. Now I have a problem - direct clutch pack often burns out. It has all Alto Red Eagle clutches. What can be the problem?

Coan built this transmission new for you?


It would help to know what valve body design is on the trans.

Is it a "clean neutral" design trans brake ? You will have a 2nd neutral after 3rd gear. Shift pattern is P N/R 1 2 3 N

Regular trans brake shift pattern will be P R N 1 2 3

Are the stiffer return springs still in the direct drum?

Is there a bleed off hole in the direct drum? Aprox .055 diameter hole

[SaM91]

Originally Posted by cobalt327

Have you checked the line pressure?

Have you had the dual feed mods done to increase the apply area of the direct clutches? It is described by Jakeshoe, beginning about 2/3 of the way down the page here.

How many frictions and steels are you using? Do you know the clearance it was set up with?

On a side note, do not put the tranny into neutral after a pass, this can overspeed the drum and scatter it and the case, etc. Don't do your burnout in low, start in second.

No, I had not checked line pressure, but I put in new ATI pump last rebuild. I will check pressure as soon as pressure gauge will be delivered to me

Yes, direct clutch has dual feeding.

Alto Red Eagle clutch pack: 7 clutches, 7 steels + 1 pressure plate. Clearance 0,130''. It is near minimum Alto specification clearance.

[SaM91]

Originally Posted by Crosley

Coan built this transmission new for you?


It would help to know what valve body design is on the trans.

Is it a "clean neutral" design trans brake ? You will have a 2nd neutral after 3rd gear. Shift pattern is P N/R 1 2 3 N

Regular trans brake shift pattern will be P R N 1 2 3

Are the stiffer return springs still in the direct drum?

Is there a bleed off hole in the direct drum? Aprox .055 diameter hole

Yes, Coan built it new, rated to hold 1200 HP.

It is regular trans break shift pattern.

No, there are no return spring in the drum.

Yes. Bleed off hole contains a small ball in there. Acts like a valve.

[Crosley]

Originally Posted by SaM91

Yes, Coan built it new, rated to hold 1200 HP.

It is regular trans break shift pattern.

No, there are no return spring in the drum.

Yes. Bleed off hole contains a small ball in there. Acts like a valve.

there will need to be return springs on the piston in the drum. usually stiffer springs are used in trans brake application.

Bleed hole is added even if drum has the OEM factory check ball valve as you mention.

there are multiple reasons for direct clutch pack failure. Low line pressure, leaks at case and center support meeting, sealing rings leaking, shifter adjustment.

The frictions can also burn if they do not release quick enough during trans brake operation. This is where the stiffer return springs help , the bleed hole helps release the clutch pack.

Clutch pack clearance is important too. A 6 friction pack I use will be set up in the area of .070 total clearance. Different builders will have their own desired clearance setup

Coan may have an additional bleed hole built in that is not seen by a inexperienced performance transmission builder.

[SaM91]

Thanks everybody for the answers!
I builded this TH400 one more time, specs:
Direct clutch - the same cluth pack (7 frictions, 7 steels, Red Eagle), drilled a hole 1,5mm, installed return springs.
Clearance 0,130''


This is photos after 3 starts with trasnbreak, max engine power.

Direct clutch pack:
Looks burned near backing plate. Slow releasing after transbreak? Need more diameter hole?


Direct clutch return springs, one installed for example. Used all springs when building.


Direct drum. Check valve and bleed hole opposite to it.


Forward clutch pack. As new. Forward drum has 1,3mm bleed hole and all return springs, but they are shorter and less harder then direct drum return springs.


Intermediate clutch pack. Burned near piston. Why?


IC burned friction.


Center support orifice for IC apply piston.


Center support return springs (3).