Boobka

iTrader: (1)

I have a 2000 Silverado V6 as daily driver, and on the way back from a trip the truck started shifting out of overdrive.

I don't think it was slipping it was a pretty obvious down shift. I stopped to get gas and the problem went away for about 20 or so miles before restarting.

The truck seems to shift fine 1 to 2 to 3 ... but that's it.

Any suggestions, plus how do I pull the codes if there are any (check engine light is NOT on)

I have the basic Auto Tap (do I need to upgrade?) or is there some other magic tool that I need?

Thanks

Ragtop 99

iTrader: (7)

it could be that the converter is unlocking, rather than a downshift. Its been years since I used ATAP, but look for engine rpm, converter output shaft rpm, and gear commanded to verify the exact problem. I'd also log misfires, TPS, and temp.

'00_Z

iTrader: (3)

Did it shift out and stay out, or did it go in and out? I had the same problem with a '94 GTP I use to have. I know it's a totally different set up but it would pop out of OD when it warmed up. It turned out being a solenoid on the side of the trans case. The part was $60 but they wanted $700 labor, so I sold it.

Boobka

iTrader: (1)

It shifted out and would stay out for a while then eventually shift back but it wouldn't stay in OD.

'00_Z - it does seem to be related to the truck being warm.

carpenb52

i have a 99 z28 and i have noticed that after driving for about 30 min it kicks out of overdrive(rpms go above 3000). If i slow down, come to a stop, or press on the brake it goes back into overdrive with no problem and will stay there for 10 or 15 min before doing it again. I have taken it to the dealership and they say i need a new transmission but this doesnt seem right. could this be a solenoid on the side of the transmission as well? please help? i plan on keeping the car.

Z28SteveA4

iTrader: (16)

it sounds like the converter is locking and unlocking. Have you played around with anything in the trans at all? Any tuning done to the trans?

ISMELLRICE

iTrader: (22)

I have same issues but I'm going 4l80 soon anyways

'00_Z

iTrader: (3)

No, it does sound like it's locking/unlocking. Get a second opinion.

z28camaro82z

check out your brake switch. this has a history of causing intermittent lockup problems.

SparkyJJO

iTrader: (11)

Sounds like the common 4L60E TCC lockup issue to me. Been there done that. Was worse in the summer when it got warm. There is a kit that fixes that by Transgo, it doesn't require tearing into the transmission any further than the valve body. Make sure you get new valve body seals and separator plate however as the original seals will tear and the plate will have some wear (might as well replace it while you're in there).

I got a "1870 code buster" kit from ctpowertrain through ebay that had everything I needed - the transgo kit, Sonnax pinless accumulators, valve body seals, separator plate, vette servo. They have one without the vette servo but get the one with the it as you'll need a new servo cover O ring anyway. Fixed my problem, the trans has about 165k on it now and works great.

ISMELLRICE

iTrader: (22)

Sparky any pointers on install? Trans has to come out?

mrvedit

No. You only need to remove the valve body from under the car. This does require draining fluid, dropping pan, removing the PWM Solenoid, unplugging the harness, unbolting the TCC solenoid and then removing the valve body. Most would then recommend replacing the separator plate too, which only involved 3 bolts to remove the 1-2 accumulator and another 3 small bolts on a retaining plate.
There are details in reassemblying everything including the 8 checkballs, but it can all be done with the trans in the car.
Might as well replace the PWM and TCC solenoids too as they control the converter lockup.

SparkyJJO

iTrader: (11)

No trans stays in the car. Just the pan, filter, and valve body come out. The Transgo kit comes with all the instructions. If you get the complete 1870 code buster kit from ctpowertrain on ebay they include the new separator plate and seals. Make sure you get the right year one as the separator plates are slightly different in various year ranges, but all 96-02 fbodies use the same plate.

I will say read the directions in their entirety and carefully. There are a few bits here and there that are easy to miss regarding drilling out some holes in the plate if necessary and the order of some valves and springs that varied through the years. You will have parts left over as the transgo kit has parts for each variation.

HighMileageC4

Is it really necessary to replace pwm selenoid.? Since the new valve should essential make this on/off, it may be overkill.

Replacing tcc makes sense.

mrvedit

You probably are right that the Transgo "fix" valve is on/off, but I have no idea how it interacts with the PWM solenoid. Its only $17 and your existing solenoid could be stuck or clogged:

http://www.transmissionpartsusa.com/...-00035394a.htm

I see lots of threads here of baffling and intermittent problems which get solved when various solenoids get replaced.

HighMileageC4

Mrvedit,

I have not shoped at transmissionparts usa. Are the selenoids GM?
Good point on the cost vs having to go into trans 2nd time.

mrvedit

I don't know if they are GM, but probably the same as your local trans shop would install. Many parts from distributors like Transtar are aftermarket too.
Glad you see my point about replacing inexpensive parts instead of fiddling with the trans for weeks.

SparkyJJO

iTrader: (11)

I didn't. I'm pretty sure like you said it just makes it on/off. Works fine for me in both vehicles.