03 Sierra 4L60E

Lately I have had a flare up in the trans in 4th gear at light throttle. seems until it has gone into O/D this happens. It shifts into 4th @ 1200rpm and then in a split second flares up and returns to 4th. Any one seen this before? No problem with 2nd since they both use the band to apply. 4th servo rings? Any ideas?

More than likely, this is a worn TCC Regulator Valve that is leaking when the TCC is locking up. The valve body needs to be removed and inspected. Sonnax makes a repair kit for this.

//2000CAYukon

The TTC valve deals with convertor lock up correct? This issue happens well before lockup. Would there not be a 1870 code if that were the case?Am I thinking correctly? Thanks

Yes TCC deals with converter lockup. A 1870 code can happen with a worn TCC regulator valve.

Might help to get a trans capable scanner on to see if lockup is being commanded when the issue happens. You can also press the brake pedal slightly (which will unlock the convertor)

If the 4th apply seal was bad, it might slip in 4th or fall out of 4th.

//2000CAYukon

Thanks for the help. I will try to locate a trans scanner and let you know...