904 clutch clearance issue

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Scott Warner

Scott Warner

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I am putting my 904 front clutch back together....only change is a multi spring unit for the front clutch, and a fresh set of Alto .083 friction and Kolene steels.
With the thinnest snapring (.065) and 4 disks in a 4 disk drum, i have a total of .030 clearance. The recipes listed in Tom Hands book all vary from .012-.022 per friction...so .048 to .088.

I am 100% positive the piston seal is seated properly.
Any ideas? The old frictions were completely smoked...no clue what was in it.
Plan B involves swapping to four .063 disks with an extra steel tossed in to make up the difference.
Thanks.
P.s.The rear clutch sits perfect at .029 with the .063 Altos and Kolenes.
 
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Machine .040 off of the piston. Or off the pressure plate. I only take off enough off the outside edge to allow for removing and installing the snap ring. Meaning there is a step on the outside edge. Kim
 
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Werent the early 904s (69) rear frictions originally specd at .083 ?

both of the flywheels are .221..

I wonder what was in there...the rear disks were slightly burnt/worn..but still showing waffle and about .070.

Machining a step makes the most sense.
 
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I always try to stay around .010 per clutch ! That seems work for me ! Unless I’m installing a trans brake , then I always use what the manufacturer says. Have had to machine the piston several times to get the clearance for a trans brake !
 
HI Scott! Thanks for buying one of the books. The .022" value came from some conversations with Gil Younger years ago and also from some of their previously published literature. I use it for the ones I build but you can most definitely vary from that when you alter the type and number of springs in the retainer.

I agree with you that .030" is pretty tight but there are some great suggestions on this string to help get it where you'd like it to be. One way is to use the thinner Altos (like Alto does in some of their Power Packs). Tom
 
VOETOM said:
HI Scott! Thanks for buying one of the books. The .022" value came from some conversations with Gil Younger years ago and also from some of their previously published literature. I use it for the ones I build but you can most definitely vary from that when you alter the type and number of springs in the retainer.

I agree with you that .030" is pretty tight but there are some great suggestions on this string to help get it where you'd like it to be. One way is to use the thinner Altos (like Alto does in some of their Power Packs). Tom
Click to expand...
Yes they use the rear clutches in the front also. Kim
 
I left the CRT multi spring as delivered (all springs installed) ...and fitting 5 thins into the 4 drum...will require machining about .070 off the flywheel....which is one third of the total thickness...I am not a fan of that...and 4 thins with an extra steel to take up space...in my mind (correct me if I am wrong) will run hotter than the 4 thick plates.
This car is going to be 60% street 40% track.And it is a B body.
 
Scott Warner said:
I left the CRT multi spring as delivered (all springs installed) ...and fitting 5 thins into the 4 drum...will require machining about .070 off the flywheel....which is one third of the total thickness...I am not a fan of that...and 4 thins with an extra steel to take up space...in my mind (correct me if I am wrong) will run hotter than the 4 thick plates.
This car is going to be 60% street 40% track.And it is a B body.
Click to expand...
1/3 of the apply piston is quite a bit , hopefully the piston doesn’t break !
 
Ok guys....many thanks..
I am headed to the machine shop in the morning to have .025 step cut off the flywheel. So .055 total with four .083 solid red Altos, and the fully loaded CRT multi spring....oughta git er done.

Or should I go .030 for .060 clearance?
 
It’s all good ! So at least .015 a piece per clutch for four clutches ! I think you said your TF-2 kit said .015 to .020 ! So you should be good to go Sir !
 
I use the same clearance no matter how many clutches there are. Don't mill the piston. Use thinner racing clutches; mix and match thicknesses. I can usually fit five with the thin .061 Alto Red Eagles. .030 will probably give you a lot of overlap in the 2-3 shift.
 
This has got to be the dumbest thread I've read in a long time. Only .030 clearance? Machining the piston instead of using thin frictions? I install 5 frictions in every v8 4-plate drum without any machining or special plates.
 
Scott Warner said:
I am putting my 904 front clutch back together....only change is a multi spring unit for the front clutch, and a fresh set of Alto .083 friction and Kolene steels.
With the thinnest snapring (.065) and 4 disks in a 4 disk drum, i have a total of .030 clearance. The recipes listed in Tom Hands book all vary from .012-.022 per friction...so .048 to .088.

I am 100% positive the piston seal is seated properly.
Any ideas? The old frictions were completely smoked...no clue what was in it.
Plan B involves swapping to four .063 disks with an extra steel tossed in to make up the difference.
Thanks.
P.s.The rear clutch sits perfect at .029 with the .063 Altos and Kolenes.
Click to expand...
Post some pics of what your up against. Kim
 
CudaFactHackJob said:
This has got to be the dumbest thread I've read in a long time. Only .030 clearance? Machining the piston instead of using thin frictions? I install 5 frictions in every v8 4-plate drum without any machining or special plates.
Click to expand...
No, that post I made refers to removing .030 to get .060 clearance. Not everyone like likes to use the thinner frictions either.
 
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