Repetitively breaking 4EATs?

unobtainium · #1 12-02-2006, 11:38 AM

This turned up in a Metafilter thread: http://ask.metafilter.com/mefi/52194

"the car downshifted quite suddenly while on the freeway, and then started to make horrible grating sounds at lower speeds. We took it back to the dealership that installed the transmission, who replaced it for free, as it was well within the 1 year warranty. And that's the pattern; transmission is replaced, a few weeks later the car downshifts suddenly on the freeway, and the transmission is shredded."

I've never heard of such a thing. It sounds to me like the TCU, not the transmission, is at fault but I only have 5MTs. Can anyone shed light into what's going on here?

ericem · #2 12-02-2006, 12:00 PM

Does the transmission have full fluid? If they aren't filled it to full you loose lubrication, then i guess the tranny overheats, then the bearings go etc, but what do i know?

Sounds like more of a mechanical thing, but i wonder if the torque converter has anything to do with this?

But still the dealer should get this problem straightened out, before warrenty is up.

firstwagon · #3 12-02-2006, 03:44 PM

I like the comment " what you have is a busted car". There's no such thing. The car has a specific problem and the dealership is not competent enough to find it. I'm amazed they are not trying harder considering they have had to eat the cost for 5 transmissions.

I would tell them if it fails again they will have to buy the car from the owner at fair market value.

The owner has been more then patient enough.

unobtainium · #4 12-02-2006, 05:23 PM

Quote:

Originally Posted by firstwagon

I like the comment " what you have is a busted car". There's no such thing.

I entirely agree. That is such a wack failure that continuing to replace transmissions seems bone-headed. There's another cause, and the dealer's failure to find it says incompetent dealer.

nipper · #5 12-02-2006, 06:23 PM

Quote:

Originally Posted by firstwagon

I like the comment " what you have is a busted car". .

The correct engineering term is busticated.

nipper

nipper · #6 12-02-2006, 06:29 PM

Quote:

Originally Posted by unobtainium

This turned up in a Metafilter thread: http://ask.metafilter.com/mefi/52194

"the car downshifted quite suddenly while on the freeway, and then started to make horrible grating sounds at lower speeds. We took it back to the dealership that installed the transmission, who replaced it for free, as it was well within the 1 year warranty. And that's the pattern; transmission is replaced, a few weeks later the car downshifts suddenly on the freeway, and the transmission is shredded."

I've never heard of such a thing. It sounds to me like the TCU, not the transmission, is at fault but I only have 5MTs. Can anyone shed light into what's going on here?

first off 5700 for a transmission is a ripoff. Secondly there is no reason i can think of for transmissions to repeatedly chew themselves up except for a poor rebuild, (at 5700 that better be a brand new just out of the shrinkwrap transmission), or something is seriously out of alignement.
The first ste would be to make sure the frame is straight and the moutns are all good. Second would be to do an autopsy on the transmission to find out exaclty why and where the tranny is failing. If they arent replacing the torque converter each time they are not being prudent. Transmissions are computer controled with a minimal valve body. Another possability is that it is going into reverse at the same time its in drive (that would be the downshift as reverse is traditionally second gear). Thats what i think is happening.
It almost sounds like they are reusing the valve body each time, and thats where the problem lies.

nipper

grossgary · #7 12-02-2006, 08:05 PM

wow. TCU replacement seems like a good place to start. i'd like to know details on the failure as well....what's the fluid look like (is it full, is it circulating properly?), what kind of pieces turn up in the fluid?

nipper · #8 12-02-2006, 08:11 PM

My sister had a BMW 3 series she just traded in for a lexus. The bmw was on transmission number 4 for the same thing, and it has about 52,000 miles on it. The transmission would engage reverse along with drive, and the same thing would happen. BMW has a seal issue in the valve body. i would guess that this is the same thing, but they kept reusing the same valve body.
TCU replacement is not the problem. The tcu has no authority as to when the car engages reverse, as it is a purly mechanical function.

nipper