ZPAK clutches
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From: Denton, Texas
ZPAK clutches We all know the 3-4 clutch pack is the weak link in the 4L60s. Anyone tried the ZPAK single sided clutches in a high HP/TQ installation? Are they better than the Blue Plate Specials? Their advertisement says thay are perfect for heavy duty work vehicles.
On The Tree
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From: so cal
Yes and no blue plate specials according to raybestos have a 30% high coeffecient of friction than the leading plate, the z-paks with the x 32 compound are only 20% high coeffecient of friction, however blue plate specials are made for race only enviroments. They are not made for cars with repeated cycling and do alot of down shifting. The z-pak is also made to take alot of heat build up with prolong clutch application like in a hghway enviroment. therefore if you have a street/strip car z pak is better way to go but blue plates are stronger if your going to do primarily racing and very little street.
hopefully Dave @ RockOn will chime in. He had me try some Altos...went thru them QUICK. Then he went back to his old standbys...i think the Z-pak. When i broke hard parts, the 3/4 clutches still looked new after 25000 hard street miles and 50 passes locking the converter in 3rd
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From: burbank ca
clutches and steels just a thought, lf your steels that face the friction plates were as smooth as polished glass how good do you think the traction would be. now if the steel plates were a little rough do you think the frictions would grab better?
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"lf your steels that face the friction plates were as smooth as polished glass how good do you think the traction would be. now if the steel plates were a little rough do you think the frictions would grab better?" No, the clutches have less area to grab when roughing up the steel plates. You want the steels to have a mirror finish if possible. Roughing up the steel plates worked ok when the clutch material was asbestos, and using type "F" fluid, but those days are long gone (late 1977 when last used). The smoother the steel surface is the more clutch area (contact surface) you have, the more holding power. Borg Warner & Raybestos came to this conclusion well over 10 years ago. Remember the fluid is designed (friction modifiers) to help the clutches grab the steel plates. Alto was going to introduce "mirror" finish steels (I was a big proponent of this) a few years back, but could not get the shops to overcome the bad habit of sanding the steels, so they dropped the idea (much to my dismay). Take a look at clutch packs that are in good shape and have well over a 100,000 miles on them, and you will see that the steels have a mirror finish. Raybestos will tell you to reinstall them "as is" as they are wearing perfectly, as long as the clutches have not had a major reduction in thickness (.003" -.005").
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For the 3-4 clutch pack I would use the 8 Clutch Borg Warner Hi-Energy setup. If the HP is over 625, I would use the 9 Clutch Borg Warner Hi-Energy setup. The vacuum modulator is what I use in all of my Performance build ups, as it is very responsive to vacuum changes, and allows for instant downshifts, and allows for more line pressure on the WOT shift into 3rd gear. I have been using it for many years, and it has proved to be very reliable.
Originally Posted by Pro Built Automatics
"lf your steels that face the friction plates were as smooth as polished glass how good do you think the traction would be. now if the steel plates were a little rough do you think the frictions would grab better?" No, the clutches have less area to grab when roughing up the steel plates. You want the steels to have a mirror finish if possible. Roughing up the steel plates worked ok when the clutch material was asbestos, and using type "F" fluid, but those days are long gone (late 1977 when last used). The smoother the steel surface is the more clutch area (contact surface) you have, the more holding power. Borg Warner & Raybestos came to this conclusion well over 10 years ago. Remember the fluid is designed (friction modifiers) to help the clutches grab the steel plates. Alto was going to introduce "mirror" finish steels (I was a big proponent of this) a few years back, but could not get the shops to overcome the bad habit of sanding the steels, so they dropped the idea (much to my dismay). Take a look at clutch packs that are in good shape and have well over a 100,000 miles on them, and you will see that the steels have a mirror finish. Raybestos will tell you to reinstall them "as is" as they are wearing perfectly, as long as the clutches have not had a major reduction in thickness (.003" -.005").
Well said Dana.....we use borgs 4l65E...with 95 thousands steel s and have had excellant results...we didn't have much luck with the z-pacs...I think the bigger issue, than the material for the 3-4's ,is the line pressure that is operating them, and addressing the cavitation problems with these pumps...just my two cents...hope this helps.... Dave
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From: Denton, Texas
Awesome information, Guys. The vacuum modulation kit intrigues me. How do you handle positive intake pressure from a blower or turbo when you use the vacuum modulation? Wouldn't the positive vs. negative intake pressure cause the module to lessen the pump pressure and then toast the clutches?
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There is a vacuum bypass valve from Trans-Go for when you use a blower or turbocharger. This prevents positive atmosphere pressure from destroying the vacuum diaphram. You now are at maximum line pressure when this happens.
