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Common Causes of GM transmission (5L40E) No Reverse and Possible Solutions
by Starless

Table of Contents:​

Part 1. Introduction
Part 2 Causes of no reverse
Part 3 Diagnostics of no reverse
Part 4 Sonnax solution to no reverse
Part 5 Installing Sonnax kits. Shops versus DIY
Part 6 Remanufactured valve body with Sonnax kits
Part 7 Installation of the remanufactured valve body
Part 8 Conclusion

Part 1. Introduction.

Ok, sorry for a long post. I've done a little bit of a research and collected some "no reverse" information here for you. The people with no reverse might appreciate it though. It's intended to outline the common technical causes of no reverse or intermittent reverse and possible problem solution options. Links to all sources are provided inside the article. Also in the source articles there are pictures and illustrations of all the valve body components that are going to be discussed here. Unfortunately I could provide only a couple of my own valve body pictures.

Part 2. Causes of No Reverse.

This part is the summarization of Bob Warnke's article # TASC-TIP-02-2009
"5L40/5L50E ***8211; Isolating the loss of Reverse or TCC concerns ". The article can be found here: http://www.sonnax.com/tech-articles/TASC-TIP-02-09.pdf

Bob Warnke, Sonnax Vice President of Technical Development, singles out 4 primary reasons of the reverse failure in the GM 5L40E transmission.

At high pressure:

1. Reverse Lock Out bore is worn. Location: Rear valve body.
2. Cross leakage into the TCC signal circuit that causes the Reverse Lock out valve to move enough to restrict reverse. There are various locations where the cross leaks can occur.

Note: A defective TCC solenoid can be the cause of cross leaks leading to the loss of the reverse function. Significant leakage can be critical and cause no reverse.

In Bob Warnke's 2009 ReMaTec presentation "Valve Body Inspection & Reaming for Repair" another reason of no reverse at high pressure is given ***8211; "excess wear at AFL bore". The presentation can be found here: http://www.sonnax.com/tech-articles/PRE-REMATEC09-RCW.pdf

At low pressure:

1. Defective TCC solenoid. Location: front valve body
2. Reverse lock-out valve stuck outward (towards the retainer)

What happens at low pressure according to Bob Warnke is the TCC solenoid's filter breaks up due to the contact with the TCC regulator valve and debris migrate to the Reverse lock-out bore and cause the valve to stick.

If that is the case just replacing the solenoid is not going to be enough to restore the reverse function. The reverse lock-out bore needs to be cleaned and examined for damage or wear.

Part 3. Diagnostics of No Reverse.

Professional transmission shops have this cool thing called the "valve body machine" using which for different tests an experienced technician can isolate a specific cause of malfunction. Some tests used are: W.A.T which stands for Wet Air Test, Vacuum testing, testing with pressure guage on TCC signal for repetitive problems and TCC solenoid quality and control. The description of the test methods can be found in the second link of Part 2.

Part 4. Sonnax Solution to No Reverse.

The company Sonnax has come up with 2 kits specifically developed to address the root of no reverse causes in these units by creating 2 kits:

1. Reverse Lockout kit (55211-11k) and

2. TCC Regulator Valve and sleeve Kit (55211-04K).

The Reverse Lockout kit helps cure: loss of reverse, TCC overheat, burned reverse clutch.
The exact description what the kit does can be found here: http://www.sonnax.com/part_summary.php?id=4960&pl=3

TCC Regulator Valve and sleeve Kit helps cure: TCC slip and ratio codes, transmission/converter overheat, delayed or no reverse.
The exact description what the kit does can be found here: http://www.sonnax.com/part_summary.php?id=4088&pl=3

55211-11k is installed in the Rear control valve body and 55211-04K goes into front control valve body.

These Sonnax kits are of great quality, address the root of the problem and cheap (I found them for $61.71+$55.73) but are they easy to install? No, no and no. Taking the valve body apart is a very serious adventure by itself. Installation of the kits is of equal if not more significant difficulty. The kits utilize the sleeves into which the reverse lockout valve and TCC regulator valve go. To install the sleeves the bores need to be reamed with special tools. There are 3 special tools that are needed: Valve body fixture (VB FIX), tool # F55211-TL and tool # F55211-TL-4.

I've contacted a couple of Sonnax tools distributors and the lowest price I've obtained was:

For the kits:

1. 55211-11K Reverse Lockout Valve Kit $61.71
2. 55211-04K Sleeve Kit and TCC Regulator Valve & Sleeve Kit $55.73

For the tools:

1.VB-FIX Valve Body Reaming Fixture $128.47
2.F-55211-TL4 $148.07
3.F-55211-TL $231.05

Part 5. Installing Sonnax Kits. Shops versus DIY.

I see 2 options to install the kits and solve the no reverse problems.

1. DIY: It's going to be extremely challenging and very expensive to DIY this project. But it's not impossible. It will involve special tools and regular tools that you might not have at your disposal for removing, disassembling the valve body and installing the kits. Sonnax web site provides detailed instructions of the kits installation process and you will need a good 5L40E transmission manual for instructions and breakdown diagrams to remove and take apart the valve body.

You can find the 5L40E manual here: http://cgi.ebay.com/ebaymotors/4L40E-5L40E-ATSG-SERVICE-REBUILD-MANUAL-4L40-E-5L40-E-/200474476320.

For TCC kit instructions see here: http://www.sonnax.com/instructions/55211-04K-IN.pdf.

For reverse lock out kit see here: http://www.sonnax.com/instructions/55211-11K-IN.pdf.

While it's not impossible the technical difficulty of this job is very high (a slight mistake can be fatal, ream the bore out incorrectly for example and your valve body is trash), time consuming and also not a cost effective project for DIY. I estimate the difficulty level to be 10 out of 10, after all we are talking about rebuilding a major transmission component so you'll need to have appropriate skills for it. The cost of the DIY can easily be between $650 and $1000 depending on the tools you have.

2. Shops: Sonnax can recommend transmission shops that have their special tools and will be able to install the kits for you. In my opinion letting the people who specialize in rebuilding transmissions do it is a much safer way to go and much more cost effective too (no need to purchase all the tools) You need to do your own research to find the shop with the Sonnax tools and how much they will charge you for installing kits.

I'm attaching a link to a web page where somebody reported to have found a shop in California to do it for them for $450. That seems a good deal to me. Link: http://www.lisabrewster.com/644/5000-crash-course-in-bmw-transmissions. See the comment by Ben Miller dated Jul 29-th, 2009. And hey if your local shop does not do it you can try to make arrangements and ship it to where they will do it for you.

Part 6. Remanufactured Valve Body with Sonnax Kits.

Option 3: This is to buy a professionally remanufactured valve body with the Sonnax kits already installed! Cost - around $500!

VBX - Valve Body Express (http://valvebodyxpress.com) is the company that remanufactures the valve bodies using the Sonnax kits and sells them through distributors. The warranty is 1 year. Their full stocking distributor is Transtar which have a location in almost every state. http://valvebodyxpress.com/distView.php?theId=1. I called the one in St. Louis and they had a valve body for me for $ 489.67 before tax and before a $200 fully refundable core charge. They have 3 part numbers: 1. BMW009 (5L40, year 99-01), 2. GM070(5L40E, year 02 and up) 3. GM072 (5L50E, year 04 and up).

And this is what they do to their remanufactured valve bodies:

1. Flat sand the valve body components to eliminate cross leaks
2. Ream the TCC valve bore and install a new Sonnax sleeve, valve and spring
3. Ream the AFL (Actuator Feed limit) valve bore and install new Sonax sleeve, valve and spring
4. Install new and EPC and TCC solenoids
5. Flush and test the shift solenoids
6. Test the completed valve body on a valve body testing machine

http://valvebodyxpress.com/products.php?theId=1 Click on "5L40E Product ID"

Note: Interesting fact here: according to the VBX description they install the sleeve kit on the AFT bore but do not install the Lock out reverse kit. I gave them a call and asked why. AFT bore is listed indeed as one of the possible no reverse causes but I thought the Reverse lock-out one would have a priority since this is where the TCC filter can get stuck. They explained to me that they vacuum tested their valve bodies and if the reverse lock out bore was worn out or damaged they would not use that casting at all. Kind of makes sense but would not hurt to have a kit on that one too.

Another company that I found that offered remanufactured valve bodies is Eurotransmissions (http://europeantransmissionscom.x-shops.com/shop/home.php ). Their 5L40E valve bodies cost $380 and are also said to include Sonnax kits ( http://europeantransmissionscom.x-shops.com/shop/product.php?productid=16353&cat=699&page=1). I could not find any additional details about them.

Part 7. Installation of the Remanufactured Valve Body

2 options to install a remanufactured valve body: 1. DIY 2. Shop

For a DIY installation I'd strongly recommend a manual. I can not include illustrations because of the copyright. The manual can be found for example here: http://cgi.ebay.com/ebaymotors/4L40E-5L40E-ATSG-SERVICE-REBUILD-MANUAL-4L40-E-5L40-E-/200474476320

1. DIY removal instructions from ATSG 5L40E manual:

"1. Using a small screwdriver, carefully remove the wire harness connectors from all the following components: pressure control solenoid, TCC/PWM solenoid, Input shaft speed sensor, 1-2; 2-3; 4-5 shift solenoids, output shaft speed sensor, internal mode switch, TFT sensor from bracket
2. Remove the internal wiring harness assembly from the transmission and set aside for component rebuild
3. Remove only 9 valve body bolts that are called out in Figure (figure)
4. Remove the valve body assembly from the case as shown in Figure (figure) and set aside for the component rebuild section
5. Remove and discard the valve body seals from the case, as shown in Figure (figure)"

In the manual there are pictures included to illustrate every step.

DIY installation instructions from ATSG 5L40E manual:

"1. Install the pre-assembled valve body assembly onto case , as shown in Figure (figure)
2. Install the proper bolts installed in the locations shown in figure (figure) and figure (figure) and hand tighten only at this time.
3. Install a 0.8 mm spacer between inside detent lever and the detent spring, as shown in figure (figure)
4. Torque all 10 valve body bolts, in the exact sequence shown in figure (figure), down to 11Nm (8 ft.lb).
5. Remove the 0.8 mm spacer
6. Install 2 new "O" ring seals into the case connector and lube with a small amount of Trans-Jel
7. Install the case connector through the case bore and while holding the connector, install the retailing clip.
8. Route the internal harness and connect all the components
9. Install the TFT Sensor into the TFT Sensor bracket
10. Install the bottom pan filter, filter seals and the filter spacer

2. Shop installation.

If you are not sure you can handle the installation yourself, that's the way to go. Find a good transmission shop and let them do it.

Part 8. Conclusion.

This write up is based on my research into the GM transmission no reverse problem. I'm not an auto technician or transmission expert. I'm just a guy with a 02 BMW 325i (auto GM) in the carport and Internet at home. Most of this info is based on the Sonnax technical documentation taken from their web site and information on the VBX web site as well as the results of contacting these companies with some questions through email and phone. I have not tried it on my car since my reverse works just fine (yet). So take it for what it's worth. If (when) my reverse fails I personally will not hesitate to buy a VBX valve body and install it myself.

The no reverse problem is usually treated like:" You need a new (remanufactured) transmission". Which is on average $4000 or even more. The remanufactured valve body is more that 4 times cheaper. It's for a reason that Sonnax created those kits. From my point of view the problem needs to be tackled as an integrated one and not as an individual component problem. Thus a properly remanufactured VB with Sonnax sleeve kits seems to me a good way to go.

Thank you for reading.

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Brilliant!

Thanks for doing the research for me!! I have the GM tranny in my 323. I have been reading all I can find about this issue. I am bookmarking this post for later(if my reverse goes south on me) use.

Excellent post!

:thumbup:
 

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Starless,

As usual your contributions to this forum are outstanding. I too have bookmarked this post, as I plan on keeping this car for a long time. My reverse works great at 45K, but i'm sure at one time or another I will need this info. Just hopefully not too soon. Thanks again for all your time and research.
 

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I was going to say the common reason for failure of the GM automatic is just that...a GM automatic.

Excellant posting. Seeing this, if I had an automatic and it experienced problems, I would tackle it. This is a perfict example of the plethora of outstanding information available here.
 

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Another great post Starless. I'm glad it doesn't apply to me, but it's priceless information nonetheless.

Wiki-fy it!
 

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Uh, oh... :eek:

Quick, batten down the hatches! Hide the women and children!!

Neil is gonna come along and go ballistic!!! :yikes:









Seriously now, Starless, thanks for your time and effort in putting all this info together. Definitely should be included in the Wiki.
 

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Discussion Starter · #8 ·
Dang man! Pay attention boys, THIS is how to make an informative post! Great job. Best part about this post (I WILL NEVER NEED THE INFO AGAIN!)
Well, when my tranny craps out I'd seriously consider hiring you for a reasonable compensation to do the swap for me (if you do not mind and I'll be your helper) rather than messing with the damn valve body :) May be.

Thanks everybody for responses!
 

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Discussion Starter · #10 ·
Doesnt jive with my experience. The failures I have seen have been a completely shredded reverse gear. Due to too thinly machined side walls.
Are you talking about GM or ZF?
 

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Discussion Starter · #12 ·
GM. I actually saved a shredded gear for a couple years but recently recycled it. I will try and find pics.
Interesting, thanks for information. Not very typical for GM.
 

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god some people here are hating on GM.....when GM recalled this transmission to correct the mistake...BMW opted out. BMW is also the one who decided to stick a GM tranny in their over priced *strictly german...dont mind the gm parts* cars.
 

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Discussion Starter · #16 ·
god some people here are hating on GM.....when GM recalled this transmission to correct the mistake...BMW opted out. BMW is also the one who decided to stick a GM tranny in their over priced *strictly german...dont mind the gm parts* cars.
I'm curious, when was the recall and was it specifically for the flaws in the 5L40E valve body?

As to your other point, I personally think that overall GM is a tight unit compared to auto transmissions in other cars I drove. Although not as fun as manual I still like the way this transmission is shifting which I can not say about many other sloppy autos.
 

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thats the same transmission that was in the rwd caddillacs ....i know because i worked for a GM dealership replacing those transmissions. was a huge TSB about it. still replace one every now and then. recall went into effect around 04? had problems in the manual shift valve body with the spool valves hanging up in the bores. it just seems odd that bmw knew about the problem and chose to not replace it when gm did.

GM's transmissions aren't great though... I've had to rebuild countless 4L60e/4L80e and 4t65E's in my day... don't get me wrong i've built my fair share of AOD/AODE/A4LD ford transmissions as well. the worst was the mitsubishi/dodge F4a33-1 trans paired to a 4200 lb car. :/

god I know too much about transmissions.
 

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Great info...
But my reverse (1999 BMW 328i - 120k miles) works then doesn't. Forward gears work great and then once in a while my reverse just won’t work. I will drive it and then it's fine. I found something about the reverse drum (or clutch) top part chips away and doesn't get good pressure at certain spot on the reverse drum. Any good fixes out there? I can have the drum replaced, but once open up the case, might as well replace a bunch of stuff in there while you are there. I found a price to replace the transmission ($2500 installed with a 4yr warranty). Seems like a fair price from what I've been finding. Still driving it, just have to make sure I can pull straight forward...just in case my reverse doesn't want to work. Any info on this would be appreciated.
 

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Discussion Starter · #19 ·
Great info...
But my reverse (1999 BMW 328i - 120k miles) works then doesn't. Forward gears work great and then once in a while my reverse just won't work. I will drive it and then it's fine. I found something about the reverse drum (or clutch) top part chips away and doesn't get good pressure at certain spot on the reverse drum. Any good fixes out there? I can have the drum replaced, but once open up the case, might as well replace a bunch of stuff in there while you are there. I found a price to replace the transmission ($2500 installed with a 4yr warranty). Seems like a fair price from what I've been finding. Still driving it, just have to make sure I can pull straight forward...just in case my reverse doesn't want to work. Any info on this would be appreciated.
Reverse drum fails mostly in ZF units, 328i cars have GM, so your problem is most likely in the valve body.
 

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Thanks Alex,
I see you have done some very extensive research on BMW transmission. In your opinion: replace the entire transmission for $2500 or just open the transmission and replace what is broken...which will probably be about $1000 (or more). I'm leaning to replacing the entire Transmission and be done with it.
Thx. John

Reverse drum fails mostly in ZF units, 328i cars have GM, so your problem is most likely in the valve body.
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Regards,
Alex
 
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