4l60e Shifting In And Out Of Overdrive

[asb151]

I have a 2003 Z71 Silverado with a 4L60e (M30) transmission. The truck has 115,000 miles. Mostly highway with no towing. Tranny was serviced (flushed) at 30K and at 80K. Fluid level is good and color is normal.

The issue is it shifts in and out of overdrive repeatedly if I climb a hill or put load on it. It only does this at a narrow speed range at roughly 45-50mph at 1200-1300rpm. If I am driving faster (on the highway for example) and I hit a hill it doesn't do it. All other shifting occurs normally during acceleration and deceleration. I am the original owner and I have never had any problems until now.

 

Any help or suggestions would be appreciated.

[[email protected]]

Mine truck has always shifted in and out of tcc lockup around those speeds and rpms. I thought it was normal.

Edited August 18, 2010 by 2001Silverado364

[asb151]

My truck just started doing this. In goes in and out of OD very quickly. Every 2 or 3 seconds.

[rodram]

you have an issue with your TCC lockup ... take it to a transmission mechanic and have it checked for codes ... a code may or may not show up, dependin on what is going on ... could be your line pressure.... could be a TCC solenoid blockage/failure (easy fix) ... or a TCC clutch wearing (requires R&R for the fix)

 

while it is slipping and shifting like that there is a lot of heat generated in the transmission.... and excess heat is bad

Edited August 19, 2010 by Rod R

[asb151]

Thanks Rod R.

I did check it for codes and there are none. Would a solenoid blockage/failure trigger a code? Thanks.

[TyeeMan]

My last truck was a 99 1/2 ton 4.8L with the 4L60E, I had the same problem. No trouble codes were set, so I took the dealers tranny guy for test drive, he brought along his tech 2 scan tool. As we were driving I told him what exactly happened and when. He picked it up on his scan tool right when I said it was going to pop out fo OD.

The problem was two fold, part of the problem was the tcc solonoid, the other half of the problem was the port on the valve body where the tcc solonoid seals off. See, the tcc solonoid is sort of a proportioning valve, it has a steel ball that opens and closes and that steel ball seals off on port in the aluminum valve body. See where I'm going here, , steel vs. aluminum? Any way, the steel ball starts to peen away the surface of the aluminum valve body, when the fluid gets warm (that's when mine did it) the fluid thins out some and leaks past this "improper" sealing surface and it messes with the line pressure.

The fix - the dealer pulled the vlave body and took it to a machine shop where they reamed out that port, installed a steel insert, so now the steel ball in the tcc solonoid can seal off on steel surface. $450.00 problem solved.

 

Hope that helps.

[GreenMachine04]

That is a very common issue with the 4L60s. Back in day the TCC regulator valve (reg valve) used to be a 2 piece design but was updated because of the reg valve wearing out the bore of the VB (valve body). Unfortunatley, the bean counters did not change the material of the reg valve so it still would wear out the bore in the VB but usually this occurs after the warranty is up on the vehicle so GM doesnt have to pay for it. The last post was absolutely correct - reg valve is steel and VB is aluminum so you know which one is going to win...

My last truck was a 99 1/2 ton 4.8L with the 4L60E, I had the same problem. No trouble codes were set, so I took the dealers tranny guy for test drive, he brought along his tech 2 scan tool. As we were driving I told him what exactly happened and when. He picked it up on his scan tool right when I said it was going to pop out fo OD.

The problem was two fold, part of the problem was the tcc solonoid, the other half of the problem was the port on the valve body where the tcc solonoid seals off. See, the tcc solonoid is sort of a proportioning valve, it has a steel ball that opens and closes and that steel ball seals off on port in the aluminum valve body. See where I'm going here, , steel vs. aluminum? Any way, the steel ball starts to peen away the surface of the aluminum valve body, when the fluid gets warm (that's when mine did it) the fluid thins out some and leaks past this "improper" sealing surface and it messes with the line pressure.

The fix - the dealer pulled the vlave body and took it to a machine shop where they reamed out that port, installed a steel insert, so now the steel ball in the tcc solonoid can seal off on steel surface. $450.00 problem solved.

 

Hope that helps.

[hitempguy]

My "04 just started doing that as well(167000 miles). Between 40 -50mph at light throttle it surges 100-200 RPM. I didn't think the lockup was hunting. I was told it could be the throttle position sensor is worn on the throttle body(drive by wire). If it is the worn valve body issue, does anybody know if there is any other fix for this issue. ie full replacement of the valve body? BTW, I don't have any codes according to my SnapOn scanner....

Edited September 15, 2010 by HiTempguy

[Barrett66]

Bringing this post back from the dead! Can someone tell me if the TCC solenoid can be replaced without removing the valve body? (03' 2500HD 4x4) Thanks for the help.

[Matthew Lawrence]

So was there any others that had this problem of the trans going in and out of OD at 40-50 and the fix was reeming the valve body? Or can you just replace the TCC solenoid? 

[AaronMcD]

On 8/18/2010 at 8:33 PM, asb151 said:

My truck just started doing this. In goes in and out of OD very quickly. Every 2 or 3 seconds.

Ur tcc or the wires leading there are probably ur prob that or your break switch is rattling  around Or something but if you have a brake switch issue this will turn off the cruise control