Join Date: Jan 2008
* No-Reverse Solution For GM Transmission *
This doesnt apply to everyone! Please read carefully
Alright lets get started. A lot of threads have come up recently about no-reverse and such. Well something needs to be cleared up. At any rate, here's my story:
About 3 years ago, I bought my 2000 328Ci (automatic). I loved it, but one day I discovered that it wouldnt engage reverse. I used my trusty friend google and searched "bmw 3 series reverse gear wont engage" like any future fanatic would do. Well it led me to this site, I was told by many of you that it was my reverse drum in the transmission and that I was screwed. I mean, this could have been the case, but it wasnt. Here is the general breakdown of how E46s and transmission are distributed: A5S360R is the transmission we are looking for
323's - Mostly ZF transmission (Rare but can have GM tranny as well), the reverse drum actually shreds, causing you to lose reverse. This is the general and accepted idea of what happens. And it is true.
328's - GM transmission, (328s have the GM tranny). I have (well had) a GM tranny as I have a 328Ci. You could get under your car and check for a green label which is pictured further down the page, but I guarantee you that you have a GM tranny if you have a 328i/Ci
Now here's the main point: People will come on here sometimes and complain of no reverse, a normal situation to fanatics. But what they dont realize and what they dont notice is that the OP might just have a 328 and not a 323.
Here is why that's important: Automatic 323's are known to lose the reverse drum, that's a fact. Automatic 328s can lose reverse as well, that's a fact. But what's the crazy fact is that 328's with GM transmissions might not have actually lost the reverse drum! GM and ZF trannies both lose reverse gear but they do it in different ways. The drum failure is the common failure on the ZF transmissions. The symptoms of the 5L40E (GM tranny) are identical, you place the car in reverse and it revs up like in neutral and does not move. And that's the point of this thread. To show you what to do if you have a steptronic GM transmission.
So GM trannies might not have lost the reverse drum? Then what is the problem you ask? There are things called solenoids in the pan of a transmission that control pressure allowing the transmission to engage gears. We all know that automatic transmissions in E46s are hydraulically driven correct? Well one of those solenoids can go bad, and guess which one? The reverse solenoid. The name which you should call it as is the "TCC and PWM solenoid"
What happens: At any rate, what happens is when the car is cold, ect, this reverse solenoid has a mesh screen on it and build up can get on the screen causing it to not be able to control the pressure to the reverse gear. This in turn is when people notice the infamous "no-reverse." Thus, people with GM transmissions wont be able to engage reverse gear and they think that their reverse drum is to blame. This is not the case!
Here's some articles that explain a little bit about the TCC and PWM solenoid:
Tell if you have a GM tranny: Bentley info and Transmission Charts (Important!)
I experienced reverse failures with my GM transmission 3 years ago but after a little bit of research that long time ago, I found that my reverse gear actually hadn't shred.
This is how I found out: I couldnt engage reverse ok, so I put my car in Neutral and rolled it down my driveway, to where I was able to engage Drive. I drove around town for a little bit, maybe to clear up the mesh screen, and then I tried engaging reverse. Lo and Behold! My reverse engaged again! This was an on and off occurrence for me for years. I never decided to replace the solenoid because I didnt really care for it. If I ever lost reverse in a parking lot, I just waited for the car to warm up and shifted around a bit. Then reverse engaged itself again.
At any rate, if you are the owner of a car that is experiencing no reverse and you have a GM tranny, try and get your car out into the open and drive around for a bit then try and engage reverse. If it comes back to life, then your solenoid is to blame. If the reverse drum was really shredded, you wouldnt be able to engage reverse again. The solenoid is in the pan and only costs around $250 to fix (labor aside). So even if you arent sure, I'd say its worth a try.
Here is the part you need, Part #4 in the diagram. Reason I say it will cost $250 to fix is because you should get a new gasket and filter:
04 Pressure regulator,convert.lockup clutch 1 24327532013 $83.5
Gasket and filter:
02 Gasket, oil pan 1 24117524707 $36.19
06 Set oil filter 1 24117557070 $132.11
Little green marker on the side indicating a steptronic GM tranny:
Some pictures of the reverse solenoid:
Reverse solenoid in the valve body
Screen that gets clogged
I'm sorry I didnt post this 2 years ago.
I think people with the GM trannies automatically associate the ZF transmission failure (reverse drum shredding) to their GM transmissions no-reverse even though the GM transmission has a completely different no reverse issue! I think most people just dont know the difference between a GM and a ZF tranny. Most take it to a shop saying they cant engage reverse so the shop just replaces the entire transmission when all that was needed was a solenoid! If you have a GM transmission and are afraid of losing reverse, when it happens, look into replacing the TCC & PWM solenoid. You don't need to replace your entire transmission!
This is just a possibility to look into, this doesnt apply to everyone!
(For anyone interested, my thread I made nearly 2 years ago)
And my quote from that thread 2 years ago:
Cheers my friends
Originally Posted by neil1138
I have a 2000 bmw 328Ci. My transmission has been acting up in the past year. I experienced the infamous "no reverse" problem. But its not the same as others no reverse problem. The car sometimes doesnt shift into reverse, reverse acts like a second neutral. But after i drive for a while in Drive, the reverse gear magically works again. This has happened 2 or 3 times. I have been reading and I dont think i have the ZF Transmission where the reverse gear completely strips because after i go in Drive, the reverse works again. I think its the TCC PWM solenoid. What should i tell my mechanic? Thanks in advance.
edit by B: changed some picture links as per PMed request from Neil
Last edited by Solidjake; 09-21-2012 at 06:52 AM.