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I have been having transmission issues so i decided to tear down the transmission and see what was going on. I bought the transmission a little over a year ago and put less then 300 miles on it so far it had been rebuilt to handle more power. I have attached some pictures. It looks like my 3-4 clutch pack is pretty burned. but what about the scarring i am seeing on the input drum and other piece? I could not find much information on either. Is that all caused by the 3-4 clutch pack going bad?
That Unit looks like it had a reverse input clutch Belleville steel plate failure at some point as well...
In the future you can use an early THM700-R4 (1982-1986) reverse input clutch stack (with a WAVED steel) instead.
See What Dana from Probuiltautomatics has available... Grab some Turbulator steels If he has some TOO!
You might as well just Contact DANA for your rebuild.
He will set you up well with a proper 3-4 clutch pack and everything else for that matter.
That Unit looks like it had a reverse input clutch Belleville steel plate failure at some point as well...
In the future you can use an early THM700-R4 (1982-1986) reverse input clutch stack (with a WAVED steel) instead.
See What Dana from Probuiltautomatics has available... Grab some Turbulator steels If he has some TOO!
You might as well just Contact DANA for your rebuild.
He will set you up well with a proper 3-4 clutch pack and everything else for that matter.
Thanks for the reply. Guess ill start getting parts for the rebuild. Can that much damage happen from only putting about 300 miles on it after a rebuild or did i possible get screwed?
Replace the input drum with a entry level 4L79.com drum kit. Double check the drum for leaks to the 3-4 clutch where the input shaft presses into the aluminum drum. Replace the reverse input drum (the one the band rides on) the inside of the drum is worn at the beveled spring. Get in touch with a reputable shop and see if they can or will vacuum check the valve-body.
So i actually emailed Dana at Probuiltautomatics and he said the input drum is ok, it does not show any unusual wear. I think i will still replace the Drum though. I will look into getting the valve body vacuum checked. As for power, its mostly a stock ls1 with ls6 intake, full exhaust and GTO air intake. So around 300hp. I was planning to heads and cam once i had it running good, but that will wait until i get the trans fixed.
So i actually emailed Dana at Probuiltautomatics and he said the input drum is ok, it does not show any unusual wear. I think i will still replace the Drum though. I will look into getting the valve body vacuum checked. As for power, its mostly a stock ls1 with ls6 intake, full exhaust and GTO air intake. So around 300hp. I was planning to heads and cam once i had it running good, but that will wait until i get the trans fixed.
I agree with Dana at pro built, I have seen and used drums in that condition at your HP level. I believed that the HP level was a lot more is why I suggested the drum kit. New bottom apply plate (the one with legs) for the metal to metal contact. I personally make sure that the bottom and top plates are not cupped/coned before I use them. Yes I check even brand new ones. 7) .080 3-4 frictions and 6) .077 notched steels comes to the tight side of .030-.050 recommended clearance. I set all my 2-4 band clearance to .125. An orange box TransGo SK will make a nice shift for it too.
Good luck on your project!!!
your band clearance is 2x as wide as it should be and a stock input drum with proper clutch setup and hydraulic integrity can handle 500 hp no problem at all
06-09-2019, 02:25 PM
4l60e Teardown are these parts bad 
