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Thread: Common Causes of GM transmission (5L40E) No Reverse and Possible Solutions

  1. #1
    Join Date
    May 2004

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

    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 – Isolating the loss of Reverse or TCC concerns ". The article can be found here:

    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 – "excess wear at AFL bore". The presentation can be found here: Sonnax - Aftermarket replacement transmission, torque converter, and high performance automotive parts

    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: Sonnax - Aftermarket replacement transmission, torque converter, and high performance automotive parts

    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: Sonnax - Aftermarket replacement transmission, torque converter, and high performance automotive parts

    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:4L40E 5L40E ATSG SERVICE REBUILD MANUAL 4L40 E 5L40 E | eBay
    For TCC kit instructions see here:
    For reverse lock out kit see here:
    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:
    $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 VBX-Guaranteed Remanufactured Valve Bodies
    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. VBX-Guaranteed Remanufactured Valve Bodies. 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

    VBX-Guaranteed Remanufactured Valve Bodies 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
    Europeantransmissions and...
    Their 5L40E valve bodies cost $380 and are also said to include Sonnax kits. I could not find any additional details about them.

    and more here in the original post Common Causes of GM transmission (5L40E) No Reverse and Possible Solutions - Bimmerfest - BMW Forums

  2. #2
    Join Date
    May 2004


    5L40-E BMW Designation - A5S 360R service manual 10 MB 128 pages

    To get to the fill plug is a desaster on that trans, I did that today on an E46 with this 5L40-E, got the fill plug finally open with this modified tool someone made a yutube

    Whenever you intend to do a filter and ATF change on this trans, FIRST always try to get the fill plug removed! Otherwise you might have a empty trans pan and cannot refill it
    Last edited by shogun; 09-26-2019 at 04:52 AM.

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