n20jeep

we own a 2004 freestar van with the 3.9 and ax4n.

one day while my girlfriend was driving it she told me about a noise she heard while pushing on the throttle, kind of a popping sound. well we had also just received the recall notice for the torque converter and i assumed it was related so we had the recall done.

the noise was still there. so i just thought to myself that it could be the CV axles, so i waited till i had an empty spot in my shop that i could bring it in and do some service work. over the next 2 weeks the noise got a little worse and you couldnt give much throttle at all before the popping noise happened.

so yesterday i brought it into the shop and checked the axles, they were fine. so i had a coworker get in the driver seat and power brake it some to duplicate the noise and so i could see if i could spot anything under the van. well, while we where doing that it did the noise pretty loud and something let go. the van would no longer move forward....


shit....


i decided to investigate myself instead of bringing it back to the dealer. i dropped the tranny to check the converter teeth to see if they were stripped, they were not. so, i tore down the transmission thinking maybe we grenaded the spider gears. well, ive got this thing completely torn down and the only thing i can find is about half of the material on the "coast band" was worn off and there were some heat spots on the back side of the band.

now, while i am pretty competent with a wrench, my experience with automatics internally is pretty small.

now my question is, anyone have any idea of what could have been causing the popping noise? and led to the ultimate failure? is it all all possible that the damaged coast band could have caused this?

any help is greatly appreciated. this is a bad time of year to half to buy a new transmission.

CatSkinner

I'm a little more familiar with the old school vacuum operated in-line automatics, but the transverse pretty much are the same thing, but bent with solenoids, so I'll see if I can muck something through. The heat marks are indicative of the band not releasing when it should, given the name, I can't help but wonder if the coast servo piston is either sticking or not getting the proper signal.

At this stage, I'd look into a rebuild, either by yourself or professionally, or replacement with a used. If you do the rebuild, I'd definitely get the piston kit. If you're looking for numbers, Aamco rebuild the tranny for my Grand Prix for 1400 which included the differential, and since it's a GTP, I couldn't do it for that price. I did pull the transmission, though.

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n20jeep

any idea though of why there is no more power transfer to the wheels? the clutches didnt look to bad either

CatSkinner

Not without actually poking it with a stick, so to speak. I know that when the vehicle brakes, the transmission engages the coast mechanisms which are supposed to release the clutches which might be why they look in good condition. Of course, I might have the description backwards but it seems that something in the coasting mechanism is causing the band to make contact, or not release when it's supposed to.

Once again, without actually seeing what goes on, I'm kinda limited on on helping to explain what's happening or not happening. I just know the theory of operation and there's only so many ways you can put this theory into application. Going over what you've said, the clutches are good, the band shows heat due to friction and has deteriorated I can only guess that the band must be engaged to take it out of coast, unless your chain has broken, but since you've taken the transmission apart, I assume you would've seen the condition of the drive chain.

__________________
Prius repellant, just add gas.