Fresh rebuild 3rd gear slip??

[RedZMonte]

Ok so i had a full rebuild (4T60-e), bushings, raybestos Stage 1 clutches, steels, transgo shift kit Jr., red stripe vac modulator, 4th clutch hub, solenoids... basically all the guts are new.. and a ~3000 stall converter... B&M SuperCooler..

Here is whats up, 1st and 2nd gear are fine but in 3rd gear drives normal untill i get ~4000 rpms then slips at partial throttle or full throttle.. the shop pulled the trans found a spun bushing (not sure what one) and burnt up 3rd clutches and a sticky modulator. replaced the modulator, clutches and bushing and reinstalled.. now same problem, literally took it home and next day drove it and slips.. Any thoughts? i don't want to keep burning up the trans obviously its not good for the shop to have to keep pulling the trans and me with my car in the shop all the time..

I have a check valve in line with the new modulator valve, so when boost comes in it blocks the boost.. they don't have the other side hooked to a vac ball like the TGPs, once side attaches to modulator and other port blocked (just blocks boost) i wouldnt think that would cause a problem would it? My stock vac mod i just boosted into it for YEARS w/o a problem

Plugged --> <-- Vac source
.......................^^To Modulator^^
Stock trans lasted 147,000 miles so i know its not a problem of to much power.. (~60K boosted) and daily beat

Anyone have any thoughts on why 3rd gear keeps slipn?

[86FieroSEv6]

Incorrect clutch stack, stack height error? Fluid foaming? Accumulator leak?

[TurboGTU]

oil pump shaft seal, maybe both the converter rubber one (could easly be forgot to be installed) and the teflon seal torn during install. Lip seals leaking on the 3rd piston or cracked leaking 3rd drum. Leaking accumulator. Weak pump, leaking boost valve. Valve body not fully cleaned, sticking valves. Did you check level of fluid?

THere's is no real easy answer.
Its one of those things that would have paid off using the oil pressure guage before and post trans rebuild to determine leaks.

[RedZMonte]

The Vac. Modulator was stuck again... Removed the Red stripe modulator and check valve. Replaced with OEM unit and boosting into it like the original setup i had and works perfect.. Moral of the story, if it aint broke.... Don't fix it! Good to go now.. Back to making the headers

S