2003 Yukon transmission trouble

[AZ-Yukon]

Looking for some insight on what has gone wrong with my transmission. I have a 2003, 2WD with ~160,000 miles. 5.3L engine. No prior transmission trouble.

Yesterday on the way home from work, it would not shift into 4th gear. After test driving it today I noticed it has less power starting from a stop and it will only upshift one gear. Could I have lost 1st and 4th, or 3rd and 4th? At 40 MPH it revs about 2000 RPM. While test driving it threw a couple codes, P0753 and P0751. Both point to Shifter Solenoid A. The fluid was a little low so I added some but that didn't make a difference.

So is it as simple as shift solenoid A going bad? Is this something I can replace reasonably easy myself? At a minimum I would like to have a good understanding of what is wrong before taking it to a transmission shop and being told I need a new transmission.

Any insight would be greatly appreciated!

[blueflamed03]

David, first off welcome to the best Tahoe/Yukon site. :)

But sadly, sounds like it's time for a rebuild, or order a stronger one online.
Luckily you made it 160K miles, mine went out at 75K or so...have a corvette servo added, and good clutches.

[AZ-Yukon]

Thanks for the feedback. That was the word from the shop. As painful as it was, I told them to go ahead and get a rebuilt one. I'm sure I'll have more opportunities for questions as it will be hard to justify updating vehicles after installing a fresh tranny.
Thanks again.

[blueflamed03]

welcome, and stick around, alot of good fellas on here. :)

[Jay]

Since you're getting it rebuilt this is kinda un-needed, but maybe this can be of some value to someone...

What about reverse? Yes, losing solenoid A can take away 1st and 4th as it's on in both gears. If no reverse, then A could be the problem. At 160k you might as well get it rebuilt or find a low-mileage unit out of a salvage yard since the friction material in the clutch packs and on the band are starting to wear thin and the check balls have beat the snot out of the separator plate by now. Bushing clearances are getting sloppy too.



For the maintenance whores out there like me, here are some "maintenance" replaceable items (low cost) that tend to kill high mileage 4L60E's:

-FLUID! Change the trans fluid and filter every 50k miles. I don't care what anyone says about "fill-for-life" fluids, they wear out just like any machine and changing it and the filter often keeps it fresh. Plus it keeps the trans from having clutch dust/mud circulating around gritting everything up, particularly the solenoids and pressure manifold assembly. DO NOT DO A "TRANS FLUSH". They are a bad idea on a 4L60E and are simply not needed... too much risk of damaging O-rings and other small parts.

- Boost valve wears out creating clearance, making a leak source. It acts directly on the main valve nearest to the pump and being worn can cause line pressure issues. Install a sonnax .490 or Transgo .500 valve as soon as you can and put in a new one every time you change the trans fluid/filter. It's cheap insurance and very easy to replace with a good set of snap ring pliers.

- The (d@mned) plastic accumulator pistons crack and leak, causing loss of normal shifting and line pressure. Install the metal ones you see on the internet. The forward and 1-2 accumulator pistons can be easily changed out with the pan down. The valve body has to come down to get to the 3-4 accumulator, but wait until you do one of the things below before messing with the 4th accumulator (as a side note you can disable this accumulator without issue, it's rather ineffective anyway. either reverse the order of the piston and spring in the case, or take them out and hammer in an old checkball into the feed hole in the case, both work just as well and will give you an improved 3-4 shift).

- Check balls beating their way through the separator plate. GM didn't make the plate thick enough at the factory for 200k+ miles and the check balls eventually wear through. There are 7 check balls in the VB and 1 in the case. I recommend replacing the plate and its gaskets every 100k miles. VB comes down for this. If you do the 100k mile replacement, you will see why I say replace it, the check balls do a number on it.

- PWM valve wear. The PWM makes the converter clutch apply smoothly... when you get in 4th gear at road speed you feel the rpm smoothly drop into lock up. It does this by pulsating the apply pressure to the converter clutch during apply. The problem is the spool valve oscillates inside an aluminum valve body, and as you've guessed it, the aluminum loses the war over many miles and causes a major leak source. This is the most common cause of the dreaded P1870 code. Transgo makes a PWM delete valve for cheap and it'll make lock-up feel like a "5th gear" shift but shouldn't be annoying. Superior makes a shift correction kit that has a REALLY stiff spring that does the same thing with the factory valve (locks it to the outside of the valvetrain, cutting off the bleed circuit). You can do this while the VB is down, or if you don't drop the VB just cut the retaining clip and rip it out, replace what needs to be replaced, and put a new clip on from the bottom. You'll see what i mean if you look at it... the clips were installed from the top side at the factory.

- Unless you've continuously ran the transmission excessively hot (220+) you shouldn't (not saying you won't) have trouble out of the electronics or one of the many O-rings in the trans. High temps will cause these parts to harden and become brittle over time which makes them more prone to failure. Simple solution is to install a good aftermarket "stacked plate" cooler. The tube-in-fin versions aren't of much good and lose more pressure across them.

As soon as you start losing line pressure, even just a little bit off the factory settings, your 3-4 clutch pack becomes a severe risk for failure. The band will far outlast the 3-4 unless you've towed excessively in 4th gear or ride in the mountains a lot with regular 3-4, 4-3, 3-4, 4-3 shift patterns.

Once you do these improvements you've about maxed out the potential durability of your stock trans without tearing it down.

A little goes a long way for us who just want the vehicle to get us to where we want to go reliably and do it at the lowest life cycle cost. Racers, you better get your wallet out if you want to stay with a 4L60E... the better and cheaper solution is swapping to a 4L80E early and regear.

[BOSS]

Might fine you coming into this thread....glad you read your PM's Jay :waytogo:


B

[blueflamed03]

jay, GREAT info....you a tranny guru? :)

[Jay]

Maybe not a "guru" so to speak, just experienced. I've built quite a few different ones, mainly 4L60Es. The tooling to build these are very expensive so I ended up selling it all off a few years ago when I left the racing scene to raise a family (buddy got killed at a meet 6 years ago, couldn't stand the thought of leaving my wife and kids behind like that for a hobby).

I also forgot to mention above... install a corvette servo (the larger servos aren't needed). You can get them for under $20 and they not only firm up the 1-2 shift, they also firm up the 2-3 shift and will greatly extend the life of the 3-4 clutch pack. Another point, if you do a transgo kit, go conservative on the shift/bleed hole sizes and DO NOT mess with the accumulation... transgo gives you the option of making the shifts very firm. Resist that temptation. Harsh shifts in a 4L60E kill the rear planetary and output shaft.

Being at home, sick for a few days gets boring. My posts have been getting way too long lately sorry about that.

[blueflamed03]

NO, love the info...excellent, great to have your knowledge around Jay!