GTO Eric

iTrader: (6)

I have just completed a 4l80e swap on my GTO.
the 4l80e is running on my 4l65e tune.
all the shift solenoids are operating correctly and i have every gear but 3rd.
3rd does not slip it just does not engage and stays in second.
using hp tuners i can see it command 3rd and the trans current gear states im in third but i get no shift.

any idea what it could be?

is it possible to have still have 4th even if the direct clutches fail to engage?

GTO Eric

iTrader: (6)

took it for another test drive. it will shift into 3rd but if i give it any more then 25% throttle its seems to slide back into second. also when i manually comand 4th and give it a little throttle it seems to slide/slip in and out. is this a sign of a problem with the direct clutch pack?

also reverse will not fully engage unless i bring it off idle slightly.

jakeshoe

iTrader: (14)

Sounds like the 3rd gear clutches are gone.

GTO Eric

iTrader: (6)

thing is this is a fresh rebuild. not even 200 miles on it. i may throw a gauge on there and see what the pressure is doing.

jakeshoe

iTrader: (14)

The reverse is a good indicator that the trans has 3rd gear clutch issues.

Where you told it was a fresh rebuild or do you KNOW it is?
Did you road test it in a previous vehicle?

I rebuild transmissions all the time that were "recently rebuilt".

GTO Eric

iTrader: (6)

i bought the trans as a rebuildable core and took it to a local shop that did the rebuild with my supplied rebuild parts.

after drving it some more it seems to get worse/better at different times and only 3rd and 4th gear affected.

the solenoids are the originaly 100K plus ones so i am going to go ahead and change all of them to see if it helps. the trans acts as if it is loosing pressure when more clutch packs become engaged. also the TCC lockup starts to surge in 3rd or 4th gear and sometimes drops out of lockup even when it is manual commanded.

GTO Eric

iTrader: (6)

so far all signs a pointing twards a pressure issure. With the scanner i can see 3rd be command then a second later it will bearly apply then two seconds later the current gear PID will change showing that their is hardly enough pressure to trigger the pressure switch.

do the shift solenoids/pressure motor have any type of filters on them? the trans was fairly dirty from a worn clutch pack before the rebuild and i failed to check/clean the solenoids.

GMCtrk

iTrader: (23)

You're running on a 4l60 tune, that's why. I'm seriously surprised the trans is even working at all.

jakeshoe

iTrader: (14)

There is a way to run a 4L80E using the 4L60E tune, it works better in most cases due to the TCC lockup strategy.

However the 4L60 tune doesn't work well without the mod, so def worth checking

GTO Eric

iTrader: (6)

trust me, it is not the 4l60e tune. all the nessasary mods to do it have been done.

slow67

iTrader: (2)

Yes, there are little screen filters on the solenoids/PCS. Might be worth replacing, since you can buy them all fairly cheap as a kit. Also as a test, you can hook up the scanner (with the key on but engine off) and click the solenoids on/off to see if you can hear them click.

Also probably worthwhile to put a pressure gauge on it and go for a test drive.

GMCtrk

iTrader: (23)

Interesting to know, learned a new tid bit there.

GTO Eric

iTrader: (6)

on todays drive (it was cooler out) i had 3rd and 4th at high throttle for the first few times. then one the trans got hotter they began to give me the same problems again until the trans cooled off again after some normal driving.

could the 2-3 or 3-4 shift valve/s be binding up when the trans is getting hotter?
the new solenoids are on the way so i am going to replace them and completely tear down the valve body and throughly clean it.

if that doesn't fix it i will be installing a pressure gauge. i have not done that yet as it is very hard to get to the port in my tight transmission tunnel but not inpossible.