4l80e rebuild on a suburban

Joined
Dec 19, 2013
Messages
5,888
Location
Fort Worth, Texas
I'd probably do .082" on the 2nd Feed with a stock converter & the Superior Accumulator Valve Spring. Then .093" for 3rd & 4th like you were already thinking.
Leave reverse be if you don't mind waiting for the Direct Apply, Be conservative if enlarging it.....Mid .060's" to .070" MAX
 
Joined
Jan 25, 2021
Messages
12
I'd probably do .082" on the 2nd Feed with a stock converter & the Superior Accumulator Valve Spring. Then .093" for 3rd & 4th like you were already thinking.
Leave reverse be if you don't mind waiting for the Direct Apply, Be conservative if enlarging it.....Mid .060's" to .070" MAX
Thanks.
Regarding the Superior accumulator valve spring.....I don't have to use it. If I left the stock spring what would you drill 2nd too? What is preferable?
 
Joined
Dec 19, 2013
Messages
5,888
Location
Fort Worth, Texas
.086" to .093".....Of coarse this is personnel preference as the 1-2 shift is quite soft on 4L80E's using 4 smooth face HE frictions. If you were using 3 Grooved Face Allison style HD TH400 Frictions.....The factory .070" feed orifice would create a similar shift time & feel as a .093" to .099" feed orifice using 4 smooth HE frictions.
 
Joined
Dec 19, 2013
Messages
5,888
Location
Fort Worth, Texas
The Lo/Reverse band NEEDS to come on BEFORE the Direct Clutch. The Direct is the Driving/Input member in Reverse & needs something to apply against. If the Directs apply first....The Reaction Carrier will freewheel & the Lo/Reverse band will cause a Bang/Shudder when it stalls the Reaction Carrier.
GM/Hydramatic had all this worked out.....But we're modifying the Direct Circuit by Dual Feeding & blocking the separate Reverse Feed portion thus further slowing the actuation of the Directs in Reverse.

Enlarging the only active Direct Reverse Feed Orifice will speed up the actuation, But you must be conservative to keep the Directs from coming on too fast.
 
Joined
Jan 25, 2021
Messages
12
The Lo/Reverse band NEEDS to come on BEFORE the Direct Clutch. The Direct is the Driving/Input member in Reverse & needs something to apply against. If the Directs apply first....The Reaction Carrier will freewheel & the Lo/Reverse band will cause a Bang/Shudder when it stalls the Reaction Carrier.
GM/Hydramatic had all this worked out.....But we're modifying the Direct Circuit by Dual Feeding & blocking the separate Reverse Feed portion thus further slowing the actuation of the Directs in Reverse.

Enlarging the only active Direct Reverse Feed Orifice will speed up the actuation, But you must be conservative to keep the Directs from coming on too fast.
I am getting ready to drill the holes. Taking into account your advice for the mods I have done I have decided on .086 (stock valve body accumulator spring) for 2nd, .093 for 3rd and .063 for reverse but have a question about 4th.
Since I have blocked the accumulator I am wondering how that how that changes feed hole size choice verses active for a firm shift feel. I guess what I am asking is if I should even block 4th accumulation.
Thank You
 
Joined
Jan 25, 2021
Messages
12
So far all I have found is CKs upgrade kit which is the 400 retainer and high rate springs. Still looking for just a used 400 retainer. Thank you.
 
Joined
Sep 10, 2020
Messages
5
Location
great bend ks
What do you think would happen to a 4L80E, if a guy was to switch to AN fittings on the trans case for the oil cooler lines and after the fact discovered that one of them was a one way flow with a check valve inside of it. (I didnt even know they existed) i'm not sure if i had it installed correctly or not. but my pressure switch manifold was a perfect parenthesis shape when i tore it down
 
Top