I recently did a stock rebuild on a 4l60e that came in with a failed band and 3-4 clutches. I tested all the usual suspects, and replaced the 3rd accumulator check ball. With everything installed to spec I installed the unit to find no 2-3 shift at wot, and delayed 2-3 shift at part throttle. After pulling it and tearing it down again I found that the servo pin bore in the case will only hold 7 inches of vacuum when traveling in it's functional range. I'm thinking that when the 2-3 shift is commanded, the oil attempting to release the band is crossing into the 4th apply piston and inhibiting the release. Has anyone else found this particular scenario with case wear. I'd like to confirm it's the issue before I search for a case and put it all back together.

 

It would take a really HUGE leak for a pin bore . Make sure no ones enlarged the solenoid AFL feeds in plate that can cause delayed or no 2-3 . Also if the solenoid has become restricted by something can do the same., But if indeeed the leak in pin bore is large enough to cause it you probably already have fried or semi fried 3-4 clutches .
Im amazed none has made an oversize pin and reemer for that yet , Or maybe they have and I have just not seen it. I have only seen that bore worn enough that at worst the teflon rings on the sonax or old 700 pin could not fix it but still and oversided pin and reemer would be a cool thing IMO.

 

Well, before I pulled the transmission I did change the solenoids thinking that possibly it was blocked. I also put another 3rd accumulator capsule in just in case I got a bad one the first time. Driving it on the lift shifting manually it has a positive 1-2 shift, and then after about a 3 second delay from moving the selector to 3rd it shifts. Once in 3rd on a drive it doesn't slip. Wide open throttle it won't make the shift. It's the worst vacuum level of a pin bore I've tested so far. But I've never heard of that inhibiting a 2-3 shift.

 

Like I said would take a HUGE leak to inhibit the shift and if anything it would be worse at part throttle as lower line,. You would more likely get a normal shift that then slipped than a delayed one. I would check the orifice holes in plate . Like I said they are so tiny it does not take much to restrict them. (EDIT by mrvedit: Frank meant to say "If they are too big" - see his correction below.)

 

I'll check them. So if they are restricted they will cause a delay? Or only if they are too big?

 

Sorry yes only if to big had a brain fart there, But I have seen where people have enlarged them mistakingly causing this type issue.

 

.....no offense here but ill be that guy. Is fluid level correct? As in the dipstick is calibrated and its low but not showing "low"?

 

One of the first things i checked.

 

Checked fluid, or checked to see if the dipstick is reading correctly? This is WAY more common than one thinks. Again, not challenging your intelligence just eliminating a common issue

I just built and delivered a unit to a friend of mine. Hes using a Lokar dipstick. I told him when he measures and cuts his dipstick to remove the pan and check the depth of the end of the stick. Sure as ****, the top of the cross hatches were at least 1/8" below the pan rail maybe even a 1/4" Factory dipsticks are known to be off as well.

 

Good point , I didnt mention as seeing he was building one figured that was covered but still good to bring it up as it is one of the most common reason for a WOT slip or no wot 2-3

 

It was correct on the dipstick, I had also checked the fluid level prior to pulling the trans the first time. As an extra measure I added an extra quart before removing it this time and there was no change in operation. I'm confident it isn't a fluid level issue. I was thinking possibly the 3rd accumulator fluid is crossing the worn pin bore into the 4th apply piston and what I'm thinking is a delayed 3rd shift is actually a 2nd to 4th shift. I don't think I remember getting another shift after the one I was assuming was 3rd. I've rebuilt about 50 of these, it's something odd for sure. No 2-3 flare, no neutral 3rd. 3-4 clutch pack and the band are still in spec for clearance.

 

Plausable , But I wouldthink a leak that large would surely burn up the 3=4 set as its sued fro 4th also

 

I forgot to mention, I did change the entire valve body when I did the 3rd accumulator capsule. I did not change the spacer plate unfortunately because I installed a new one when I did the rebuild. The part number I used was

24244053

The vehicle is a 2000 Camaro Z28

 

The AFL holes are .093 in the new plate. The original plate they are about .050 do you think that could be the issue?

 

If the AFL feeds to the solneoids are near 2x larger then yes very well could be they could flood the solenoids and would become more likely to do so as throttle increased. slowing or preventing the 2-3 shift. The 1-2 is not as suceptavble as it has a strong spring pushing it back.

 

Put an entirely different transmission in the vehicle. Same problem. Now what lol

 

If you have data logged and the comand is being given i have no idea , If its not then sensor or pcm issue

 

Reset "Shift Adapts"!

 

I also want to make certain that This Part was installed:


And not this Part:

 

Any chance this vehicle has a non-stock tune on its PCM/ECM?
Generally at WOT, both(!!) the tuned Speed AND RPM must be met before the shift occurs.
Part-throttle shifts are based only on Speed. With very low tuned line pressure the shifts could be very slow. So could be a very bad tune.
A bad MAF signal could indicate mild throttle, but if the power is actually high, the trans will slip a lot (bad!) before completing the shift.
Can you scan things like MAF signal and the trans PCS amperage level?