4L60E shudder
 

I recently started having an issue with my 1998 pickup. The trans was rebuilt about 1/5yrs ago. When built, I went with my own supplied torque convertor. I have been unhappy with it since install, as I can tell it wasn't balanced correctly. I'm now assuming they also rebuilt the lockup clutch badly as well based on my issue...

I will randomly get what I believe is a torque convertor shudder on the freeway, followed by the TC unlocking for a mile or two before locking back up. I haven't felt the problem on side streets. Its random and not often at all, except for one long on ramp I take twice a week. After climbing up that 1/2mile uphill ramp it will shudder and unlock the TC when I reach 4th gear every time. The shuddering followed by unlocking for a bit before going back to normal makes me think the TC clutch is slipping with a heavy load and the truck is noticing and unlocking for safety?

Re: 4L60E shudder
 

Wasn't 4L60E but 8L60E in 15 Silverado behind a 6.2. It developed converter shudder while still under warranty. I thought for sure they would replace the converter. Instead they used some type of trans flushing machine and ran about 25-30 quarts of tranny fluid thru the trans. It worked. Never had a problem after that.

Re: 4L60E shudder
 

This dropping of convertor lockup is usually a sign of a bad ground in the lockup circuit or a bad convertor.

Does the fluid appear burned up?
Was a shift kit installed when the trans was rebuilt?

The lockup clutch is not normally engaged below 45 mph....and should immediately unlock under full throttle....it should not be lugging and holding on, as doing so will burn it up quickly.

Re: 4L60E shudder
 

Fluid is clean. No shift kit, well maybe little pieces of one were used lol. Clinbarger did a build thread: https://67-72chevytrucks.com/vboard/...d.php?t=812006

Lockup on this truck will happen as low as 38mph indicated in 4th gear. Been that way for 16yrs and 140k miles that I've had it. You have to be really just cruising at that speed though, and about any amount of throttle unlocks it.

Re: 4L60E shudder
 

If you do a search on the net, you'll find others with the same issue. More often than not, it seems like the TCC solenoid or valve tend to be the issue. If it goes on too long, your torque converter is toast. I know thats not what you want to hear.

When your trans was rebuilt, did they rebuild the valve body? I know sometimes a rebuild is just clutches and steels and the rest is forgotten about.

If you do end up tearing into the trans, I'm going to recommend s TransGo or Sonnax shift kit. They have valves, springs and misc. Items that freshen up the valve body. I used a TransGo kit on a 700R4, it made a huge difference.