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Forward clutch piston seal question

9K views 12 replies 4 participants last post by  gregaust 
#1 ·
Tried to get this question answered definitively in another forum. I'm rebuilding a c6 & was unable to install a lip style seal in the forward drum. In fact I damaged 2 in the process even when using a seal tool. It was just too tight. I eventually just used a square cut seal around the forward piston & seemed to seat perfectly. Air testing on the bench confirmed that it was holding pressure. However I have been told that there are two different style pistons used, one that has a slightly recessed lower land that accommodates the lip style seal. Mine is this style and it is from a "72 Lincoln. The question is will I have any problems using a square cut seal instead of a lip seal? I don't specifically remember what type of seal was used when I stripped the transmission.
 
#2 ·
Ran into the same situation 5 yrs ago.The lip seal just will not fit.Used the square cut seal and the trans is still working good.Don't know what yrs and applications the square was used but wouldn't mind finding out.Lesson learned by me...don't remove the old seal till you're ready to install the new one.
 
#3 ·
Seals

The lip type seal will not fit in a square cut psiton. There must be a small relief on the piston.

If a square cut seal is used in a lip seal piston there is a possibility of it flipping over.
 
#4 ·
I don't remember what type of seal I removed originally...it's quite possible it was in fact a square cut seal. However I attempted to install a lip seal since I could see there was a very slight relief in the bottom land of the piston. But seriously there was no way that seal was going to fit & believe me I tried. It makes sense that there might be a possibility that the square cut seal could flip but I really don't think so since it seemed to be a near perfect fit.
 
#7 ·
When I inspected the drum for the smaller lower land it initially looked the same as the top but when I looked closer it did seem that it was slightly recessed compared to the top. How obvious would the difference be? It did look very close to the top. Mine is out of a '72 c6. I'd like to know if the square cut seals were used for this year.
 
#10 ·
Thanks so much guys for that information...wish I hadn't already assembled the tranny. I would have liked to check these measurements. Now I guess I need to know what piston was used for year 1972 in the big Lincolns to confirm whether I used the right seal.
 
#11 ·
By the casting #s on these 2 pistons,square cut from 69 thru 75,,,,76 thru???,lip seal,if...these were the only 2 pistons used.Must have been a different piston from 66 thru 68 and a change over in 69.By this "logic",you should be OK if it's original and hasn't been worked on or exchanged.
 
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