4.8is transmission journey from broke to ballin'

[bcredliner]

Can't help you on programing the transmission. I suggest that when the pan is pulled to change filter you also change the temperature harness as preventative maintenance. I know only enough about transmissions to be dangerous. Suggest you search transmission threads for solutions to your problem. IMO there are very few members that know enough about transmissions to sort through what can be several causes for the same symptoms.

[Junkycosmos]

Originally Posted by bcredliner

Can't help you on programing the transmission. I suggest that when the pan is pulled to change filter you also change the temperature harness as preventative maintenance. I know only enough about transmissions to be dangerous. Suggest you search transmission threads for solutions to your problem. IMO there are very few members that know enough about transmissions to sort through what can be several causes for the same symptoms.

Agreed ..

drop pan,
new filter (BMW parts counter)
drop valve body (its easy if you can drop your pan you can do it)
New metatronic seal (round electrics plug seal)
valve body seal , 4 tubes within trans (BMW)
new trans temp harness
refill with correct fluid
get the fill level correct

maybe go route of the programming updates after that ...

[Junkycosmos]

Just make sure the fluid is not low. I cannot prove it but I suspect that 90% of the transmission issues with this car are due to low fluid. It’s common these trans loose a little bit due to the side seals, open vents, so many heating ans cooling cycles. Then we know they act horribly when the fluid is even slightly low. Heck, take hot fluid, put it in a cold tranny and the fill level will be low or better yet do a fill on non level ground.

Yes the trans parts wear but the miles at which they wear are double what is going on in these units hydraulic wise. Key is to remember these transmissions are hydraulic driven for all they do. Without proper hydraulic pressure (low fluid, poor pressure seal) the transmission cannot function properly. Then take the amount of forces at play (weight and torque) you quickly burn up the mechanics.

Way too many trans are “diagnosed “ as failed clutches: I call bs, you don’t burn up clutches unless they aren’t shifted right (electrics and hydraulics).

[SigBoi]

Originally Posted by PropellerHead

Trip 1:
Drop the tranny, replace a gasket that frequently fails and causes rough shifting. Gasket not obviously damaged. Transmission fluid flush and fill. Same filter- replaced ~25k ago. Agree to replace filter and fluid at next interval- ~90k miles.

Mark off driveshaft to look for slippage. None found.

Diagnose rough idle through codes. Replace engine module that handles the same items as faulted in codes.

Diagnose air suspension. I heard audible air leakage while parked. Turns out this was a wheel problem. Found some leaking stems. Leveled the suspension.

Cost: $700

Result: No rough idle! No more rough 1-2 shifts when cold! Sport auto mode WORKS without hanging on to a gear like a freshman virgin does a senior suitor. It was SO nice! I was happy! But could I be MORE happy?

What was the engine module that was replaced that fixed the rough idle? I heard the IVM could affect this, and I've replaced mine with no effect to cold rough idle.

[bcredliner]

Originally Posted by SigBoi

What was the engine module that was replaced that fixed the rough idle? I heard the IVM could affect this, and I've replaced mine with no effect to cold rough idle.

There are several potential causes of rough idle. Some of them are--secondary air pump, spark plugs, failing coil, vacuum leak etc. Troubleshoot rather trying to solve it with new parts that may or may not be the cause.

[SigBoi]

For sure, the IVM I replaced to fix the other issues it was causing, like weird shifting and random rough starting, which it did. I also heard it affected cold start rough idle, but it didn't do anything for me there.

OP said this module that he replaced cured his cold start rough idle, which I'm experiencing now. Would not hurt to know what module this is while investigating root cause. I'm going to get a smoke test done next to see if there are any vacuum leaks, then onto the next check.

[amancuso]

Originally Posted by SigBoi

For sure, the IVM I replaced to fix the other issues it was causing, like weird shifting and random rough starting, which it did. I also heard it affected cold start rough idle, but it didn't do anything for me there.

OP said this module that he replaced cured his cold start rough idle, which I'm experiencing now. Would not hurt to know what module this is while investigating root cause. I'm going to get a smoke test done next to see if there are any vacuum leaks, then onto the next check.

I'm wondering if I have an IVM issue as well. I noticed sometimes the car idles a little weird when first starting it, also the way the transmission shifts is weird, like it shifts too early leaving the car with no power, which makes me have to push the accelerator further for it to downshift again.

[amancuso]

Here's some further info on the weird behaviour of my transmission...

"My new to me 4.8is w/ 83k miles seems like it shifts too quickly on moderate throttle (speed limit of 35-45) and to make it actually go it has to downshift. It also does something weird very rarely but has done it about 10 times over the past 3k miles. When traveling at lower speed, say 40, and I try to accelerate gingerly without stomping the pedal, it feels like the transmission shifts halfway, makes a whooshing sound then bumps into gear, almost like it's sliding before actually shifting into gear. I am getting the fluid changed along with that square adaptor, 4 small hoses and the electrical plug gasket changed, also checking the transmission programming and adaptations reset this weds. I guess my next step if this doesn't work is the solenoids or even whole mechatronics unit change?"

[twinspool]

Originally Posted by amancuso

Here's some further info on the weird behaviour of my transmission...

"My new to me 4.8is w/ 83k miles seems like it shifts too quickly on moderate throttle (speed limit of 35-45) and to make it actually go it has to downshift. It also does something weird very rarely but has done it about 10 times over the past 3k miles. When traveling at lower speed, say 40, and I try to accelerate gingerly without stomping the pedal, it feels like the transmission shifts halfway, makes a whooshing sound then bumps into gear, almost like it's sliding before actually shifting into gear. I am getting the fluid changed along with that square adaptor, 4 small hoses and the electrical plug gasket changed, also checking the transmission programming and adaptations reset this weds. I guess my next step if this doesn't work is the solenoids or even whole mechatronics unit change?"

I dont have much to add however, being that you are in there already, I would also change out the solenoids while you're in there..

[upallnight]

Instead of changing the whole mechatronic unit, I would send it to Gary to have him rebuild the one you have now. He will send the solenoid out for testing and if they are bad he will have them replaced.

Here's a video of him overhauling a ZH6hp26 valve body.

https://www.youtube.com/watch?v=MlDVqH9VEgQ

Dealers in his area send their cars to him to overhaul the trans.