99 Sierra 4L60E 1-2 Slip at 206,000

govener71 · January 30, 2012

I have been looking around for some definitive help on my 99 GMC Sierra. Now I just need some opinions and possible experince from all of you. My truck in the last year has slipped 6 times from a stop light/sign. Most recently it did it twice in two days both times on my way to work after driving 20 miles. Everything flows smooth and catches in all other gears. I am taking it in to have a good local shop check it over.

My question is, would it be wise to install the .490" boost valve and a the 1-2 corvette servo with 206,000 miles on it?

I have been going back and forth about the larger boost valve and the servo becaues I do not know the mechanics of a tranny real well. Would the increase in pressure put too much strain on other parts that would then cause the tranny completly go out?

Also I had the fluid exchanged last time now it is time for the filter and fluid, I have no other tranny problems and the truck is in good shape with no leaks of any kind. Here are the parts I am looking at.

http://www.oregonperformancetransmission.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=OPTI&Product_Code=SNX-77898E-K

http://www.oregonperformancetransmission.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=OPTI&Product_Code=NTP-K51828C&Category_Code=4L60E

brainpause · January 30, 2012

I'm not an ace on transmissions either, but here goes. I put the 1-2 servo and the 4th hold servo in at around 45k miles, IIRC. I then took it to a trans shop. They said it was fine, but hesitated a little when I told them I had just put in those servos. He did say, though, that at that mileage it was probably okay. He said something about wear patterns that would be more prominent with more miles.

At 206k miles, if it's an original trans, you may be looking at a rebuild soon anyway, even if it wasn't slipping. I wouldn't do the servo myself at this point.

Larry

govener71 · January 30, 2012

Thank you very much for the reply, did they by chance mention at all the boost valve? The reason I ask about this is because I read a few different places that is should be replaced every time the fluid filter is changed, every 40-50,000 miles. I am not sure if I just go with a stock boost valve, .470", because it would be less inline pressure on the shifts compared to the .490"

brainpause · January 30, 2012

I know nothing about that. I've read a bunch here, and I've never heard of that as periodic maintenance.

AirForceAngler · January 30, 2012

At 206K miles, the slippage isn't due to low line pressures but fatigue. If you got that many miles out of your trans without a rebuild, consider yourself lucky and drive it till it fails. Get it rebuilt back to stock and keep going. I've never heard about that valve needing replaced either.

govener71 · January 30, 2012

I looked into it more on the sonnax web page and another silverado forum and it is a "tranny tip". Not a necessity, but possibly a good idea.

Shatterz · February 1, 2012

Personallly I wouldn't touch that transmission until you are ready to get it rebuilt or it finally gives up the ghost. No modifications should be done with that kind of mileage other than a rebuild. You've gotten probably around 40,000-60,000 more miles than most people typically get out of a 4l60e until it needs major repair. Consider yourself lucky and consider that transmission on borrowed time.

uh6tdrvr · February 2, 2012

DON'T DO A LINE FLUSH! It will only speed up the process, a GOOD shop will tell you that.

Also keep in mind, just because this is the first hickup, it won't be its last. At 206K, suck up the rebuild sooner than later. Plan for it very soon or it will plan it for you. You can find a reputable shop and get an estimate or if you are mechanically inclined you could order one and do the swap yourself for alot less. They aren't that hard, you will just need a extra hand to do it.

If you get an estimate and you are encroaching on 2K (cause it probably will), Personally, i would get a new one. With the rebuild, you will more than likely get a 12 month/12K warranty where with a new GM unit you will get a 3yr/36K warranty and for a couple hundred more you will get exactlly what you just put 206K on.

https://www.google.com/ and put 4L60E in the window

$1,558.96 new @http://www.gmpartsdirect.com/