still have a reverse problem with rebuilt auto

[Russell]

Left it with my indy over the weekend. He even drove it home and tried it two cool mornings. Lowest temp was about 22 degrees. As I have said before, my going out of gear in reverse is random and did not happen for him. We relaced the shift cable and rechecked fluid levels. He is most concerned and he is going to contact the rebuilder Precision European Transmission in Ca. They may start with replacing the valve body.


Following is a description of the problem
Problem usually happens on first start of day. However it has happened at end of the work-day about 9-10 hours after first start. Problem seems more pronounced if car sits for a couple of days. Also, problem happens randomly but seems to occur more often on a colder day when temperature is below 40 degrees especially when near freezing.

Follows is a typical cold start. Start car, put in reverse and use “moderate” throttle.( problem is less if you let car move with no or very light throttle), car starts moving and engine revs as if in neutral, then gear engages. I have not changed throttle position. This can happen 1 to 3 times (If I reduce throttle, gear engages). Car can die at that point or may operate normally. Puzzling

[Russell]

Latest from the trany rebuilder. It may be an electrical issue. Areas to check are the trany contoller, or solenoids/valve body. I am supposed to check to see if the "R" on the dash blinks or goes out when I have a reverse episode.

[whiskychaser]

I think the idea is you may have a simple shift lever switch fault but am sure you would have noticed if the 'R' light was out or flashing.

AFIK, reverse on your tranny is controlled by a. reverse lock out valve b. reverse shuttle valve c. pressure valve. I think a. may be a known issue but if any of them stick reverse will not engage properly. In the absence of codes, VB seems the place to start

[Russell]

I think the idea is you may have a simple shift lever switch fault but am sure you would have noticed if the 'R' light was out or flashing.

AFIK, reverse on your tranny is controlled by a. reverse lock out valve b. reverse shuttle valve c. pressure valve. I think a. may be a known issue but if any of them stick reverse will not engage properly. In the absence of codes, VB seems the place to start

Thanks. No problem on a warm day or warm start. Get below 30 degrees and problem often occours.

[Tiger]

It sounds more like seal issue to me... the question is whether it is in the valve body or the clutch packs. You got diagnostics to do.

[Russell]

The rebuilder stated that the valve body parts are new and one or more components appear to be sticking when temperatures drop near freezing. They usually "work loose" with mileage. For example it was perfect today with a low temp in the 50s.
However, before they replace components that want my shop to use Lubguard Red transmission additive to help free up the sticking component. I see not problem with this as there is no cost to me. From all accounts this is an excellent product. See link below.

http://lubegard.com/~/C-112/LUBEGARD...uid+Protectant (http://lubegard.com/~/C-112/LUBEGARD+Automatic+Transmission+Fluid+Protectant)

[Tiger]

That's good to know... went to the website and learned something... which is probably why transmission with extra cooler last longer and is especially important when towing. I installed a towing kit on my Acura MDX and part of the package is the transmission cooling fins... sort of like a pipe with fins radiator... it connects IN LINE with existing radiator that is part of your cooling system... so it will cool down the transmission fluid more on highway while on local road, the existing raidator will cool more.

So, I suppose we can do that with any cars as long we have room for the extra radiator and rubber tube to work in line with existing hoses.

In their articles, I notices they were comparing to standard ATF fluids... not synthetic fluids... so it is very probable of the fluid burnout just like regular engine oil. However, it is all about additives that makes lubricating fluids great.

[ryan roopnarine]

The rebuilder stated that the valve body parts are new and one or more components appear to be sticking when temperatures drop near freezing. They usually "work loose" with mileage. For example it was perfect today with a low temp in the 50s.
However, before they replace components that want my shop to use Lubguard Red transmission additive to help free up the sticking component. I see not problem with this as there is no cost to me. From all accounts this is an excellent product. See link below.

http://lubegard.com/~/C-112/LUBEGARD...uid+Protectant (http://lubegard.com/~/C-112/LUBEGARD+Automatic+Transmission+Fluid+Protectant)

Lol que? I aint no big city transmission scientist, but I gotta wonder why new valve body components would be sticking (particularly if the issue ends up being related to solenoids). Did the rebuild option you chose include new electrical parts?

Could someone more versed in transmission operation and the pragmatic concerns of rebuilding explain if this "sticking situation" makes sense?

[Russell]

Yes the rebuilder used new parts and I also find sticking component a bit odd. The rebuilder did dyno test the trany but only at calif temps. I am playing this out as my shop wants. I have used this BMW indy shop for over 20 years on various BMWs so I trust them.

[Russell]

The rebuilder stated that the valve body parts are new and one or more components appear to be sticking when temperatures drop near freezing. They usually "work loose" with mileage. For example it was perfect today with a low temp in the 50s.
However, before they replace components that want my shop to use Lubguard Red transmission additive to help free up the sticking component. I see not problem with this as there is no cost to me. From all accounts this is an excellent product. See link below.

http://lubegard.com/~/C-112/LUBEGARD...uid+Protectant (http://lubegard.com/~/C-112/LUBEGARD+Automatic+Transmission+Fluid+Protectant)

Lubegard red added today. We shall see.

[whiskychaser]

Could someone more versed in transmission operation and the pragmatic concerns of rebuilding explain if this "sticking situation" makes sense?

This is how it works:
http://i290.photobucket.com/albums/ll280/whiskychaser/img068.jpg
OP, if you want the full manual I will try to find the link

ATF is simply diverted from one direction to another to make one clutch engage and select that gear as opposed to another. They use solenoids and sprung valves to achieve it. Could be there is a lazy solenoid that works fine when things have expanded when they warm up. Similarly, if you install a weak spring or leave it out (dont laugh!) you will have problems.
Not relevant to this but a reasonable comparison is the 530i with the 2-3 gear flare problem. Two different return springs can often sort it.

[Russell]

This is how it works:
http://i290.photobucket.com/albums/ll280/whiskychaser/img068.jpg
OP, if you want the full manual I will try to find the link

ATF is simply diverted from one direction to another to make one clutch engage and select that gear as opposed to another. They use solenoids and sprung valves to achieve it. Could be there is a lazy solenoid that works fine when things have expanded when they warm up. Similarly, if you install a weak spring or leave it out (dont laugh!) you will have problems.
Not relevant to this but a reasonable comparison is the 530i with the 2-3 gear flare problem. Two different return springs can often sort it.

Cool way to explain.

[Russell]

Lubegard red added today. We shall see.

Looks like I will be getting a new trany. I have put about 5,000 miles on the rebuild since last November. California rebuilder is going to send it to my indy BMW shop here in KY in a couple of weeks.

A previous post indicated the rebuilder wanted Lubegard red added to trany to "free up" components. The Lubeguard had no impact on the reverse problem.

Outside of the cold weather reverse problem (would "jump to neutral" while backing up only freezing weather) trany is perfect. Problem happened this week with overnight temps dropping into the mid 30s.

[Tiger]

Good to kniow that your rebuilder is honoring their warranty.

[Russell]

My indy shop just put in the 2nd rebuilt trany after having a cold weather reverse issues. I drove it about 7,000 miles before replacing it. No cost to me.

36,000 mile warrenty starts again. The rebuilt trany was delieved to my indy shop in a well packed plastic box with a coolant line/cooler flush kit and already already filled with trany fluid.