Autobox: Reverse gear lost temporarily in the cold

[eisdielenbiker]

Hi,
always when backing out of my garage I have a phenomenom with my automatic gearbox BW35. It is rather cold at 1 to 5 degrees C. Car starts fine and i put in R. At the moment when i leave the garage over a very small downward step at the bottom of the door frame the gear disengages. This happens every time then. And only when cold. Still i always manage to shift to N wait a second and reengage R successfully. And everything is fine although a little reluctant. You see engine and autobox are cold. So i cannot really blame one or another. Oillevel in autobox is at the middle between low and high. I intend to add about 200 ml and see what will change afterwards. Is that a good idea or are 200 ml too much ?
Thanks
Mark

P5B,1971

[enigmas]

Mark, you need to check the gearbox fluid when the vehicle's transmission is at operating temperature on level ground. Do you know how to do this? If not there are many posts on this board about how this is done or someone will "chime" in again on how to do this.

From what you state the gearbox linkages may be slightly out of adjustment so that the gearbox pawl is not properly locked to it's 'correct' position or is being pulled out by movement of the drive train as the back wheels hit the ridge when reversing out of your garage. Check your engine mounts and steadiness of the engine gearbox assembly.

Also put the vehicle on stands (under the back axle so the drive-line is in it's 'normal' operating position) get underneath and a have a friend move the gear-lever through the range of positions. The small lever on the gearbox should click into each position. Check to see there is no binding or rocking action that may cause the lever on the gearbox to disengage. This is not rocket science only requiring observation and a patient methodical approach. Once the linkages click through nicely ensure the gearbox transmission fluid is toped up correctly. Ether way... too much or too little fluid leads to problems.

One last comment since you weather is so cold, warm the engine and transmission for 5 mins before driving off.

[eisdielenbiker]

Yes i have checked the fluid level according to the handbooks and the advise from the forum. The 'ridge'-theory sounds reasonable. The gear shift prawl could indeed be moving by effect of the drive train being set apart. I will check this next time. However the notorious gearbox mount is in good condition. Engine mounts are not really clear to evaluate. What is the litre difference between low and high level mark of the late gearbox ? I just wonder because of the cold weather nature of the problem.
Mark

[Phil Nottingham]

Cold weather does affect these especially if dirty/old/wrong type ATF as does wear and imminent failure.

So much has been written about this on here and the above post is agood starter for one but the important thing to understand that this performance is NOT normal and something is amiss which may or may not (usually not) be serious but will become so if ignored in time

[eisdielenbiker]

I am about to sort a few things out with the box next year. I already have a pistol shaped BW35 filter from JRW (i fear it is the wrong one) and a new sump gasket plus 9 litres of non Dexron ATF fluid bought locally. Besides i will look for the brake band adjuster under the sump pan. Its a pity that these things are not to be done in a hurry on these cold days.

[harvey]

Most of the brake bands that used to have the manual adjusters inside the sump (front band) have now been fitted with the later self adjusting front servo, which works very well, and is worthwhile fitting if you are unlucky enough to still have the early manual type. The later type filter that you have will only fit if you have the latest (303 series) valve block fitted.

[mcgill]

how can you tell,if its a 303 series,i too have just recieved the pistol shaped filter,when one in box is is the other one ??

[harvey]

Mar 18, 2010 9:45:38 GMT mcgill said:

how can you tell,if its a 303 series,i too have just recieved the pistol shaped filter,when one in box is is the other one ??

Looking from the outside it's not possible to tell what type of filter you need, because there is no way of knowing what internals you have fitted. If you can post a picture of the inside of the box once the sump is removed, preferrably with a good view of the rear of the valve block where the rear filter would be, if fitted, and a side view of where the normal filter fits, then I should be able to tell you which filter should be used.

[mcgill]

heres this one i took earlier

[harvey]

That's the early type by the looks of it, so the later pistol type filter won't fit, you need the flat strainer. If that area where the rear filter would sit is about 1" deep then it's the early type. You can also see at the front filter, about 1/2" between that silver end plate on the side and where the filter screws on. If you want to prove the point, fit the pistol type to the valve block, and try to fit the sump, and you won't be able to because the filter hits it. It's the early front servo you have there too, so regardless of what it says on the casing about being a 303, internally it's full of old bits. I can't see a magnet in there either. Nice fresh fluid though........

[mcgill]

oh yes there was a magnet,in the sump along with one of those flat head screws stuck to it.....
.......ill get the filter changed.....cheers harvey

[harvey]

All those internals are what I would expect to see in a 7FU, but after all this time you never can tell. There should be a restrictor on the valve block end of the forwardmost pipe that goes to the front servo if you wanted to pull the pipe out and have a look. When you mentioned a 303 I thought that was what you had.

[mcgill]

cheers harvey,just come back from garage,sump wouldnt fit ......

[eisdielenbiker]

Odd enough that my sump pan fitted over the pistol type strainer....
Cheers
Mark

[harvey]

Mar 21, 2010 17:56:10 GMT eisdielenbiker said:

Odd enough that my sump pan fitted over the pistol type strainer....
Cheers
Mark

That will be because you have the late type valve block which it is designed to fit, then..............

[eisdielenbiker]

I don't really see a different valve body in my P5's box besides from the colour:


But what I see is possibly an automatic front brake band adjuster, at the front servo(?), bracketed by number 4 up in the manual page:



As they had described rear band adjustment from top of the box but not front band adjusting I suppose that manual mentioned here

roverp5.proboards.com/index.cgi?board=Roversfromaroundtheworld&action=display&thread=4046

refers to a (my) later autobox. What do you think ?
Mark

:-) Watch the droplet getting loose in the photographs lower left corner :-)

[harvey]

That is indeed the later self adjusting front servo, and if the late type pistol shaped filter fits without fouling the sump it is the later type valve block too. It is a bit difficult to see from that angle, but the depth of the rear filter housing would seem to confirm that, I can't see the depth at the front, but as I say if the late filter fits, it's a late type valve block. Nice looking hedgehog in there too.

Like the pic of the droplet, very arty!

[harvey]

If you use that leaflet, even though it purports to be from the genuine Borg Warner manual, you're going to get into real trouble setting that front servo, because the measurements given on there are incorrect. I kept looking at it knowing it wasnt right, and am surprised even now that they've managed to get both the Imperial and Metric figures wrong by the same amount. Still it's only out by a factor of 10.

I suggest you use the WM rather than that sheet.

[eisdielenbiker]

Thanks for the valuable hint on the measures. I didn't bother to change a running system. If it is selfadjusting then who cares. So I will look for the rear brake band only. And I will countercheck all given measures in deep from now on...
Btw. the 'pistol' fitted but as the 'old' strainer was easy to clean I just put it back on last autumn. Usually you wont ever need a new filter strainer at all.
Mark

[harvey]

The problem with fitting the flat strainer to a valve block designed for the later pistol type is that it wont be drawing up fluid from deep enough, and so any surge, or a slightly low fluid level will cause problems. You do end up needing to change the filters because they get blocked and start whining. Yours is designed to be fitted with the late type, so use it!

[mcgill]

filter/strainer still not arrived yet but i noticed when fiddling this pipe was lose,..i pushed it back in the case but where does the other end of the pipe go????does it plug in anywhere??
my magnet is a bit wimpy so i was going to put in a 2mm so called super magnet.......is this a wise move?
also none of the flat heads have spring washers as in parts book,should i fit?

[harvey]

Providing the pipes are pushed fully home the sump (once fitted) stops them falling out, although a slight bend in them can tighten them up if needs be. The one you have shown as loose is the outlet to the cooler from the converter, you won't get to the other end because you'd need to get the valve block out of the way to see it, because it fits into the front pump, so just make sure the pipe is pushed home into the fitting, and that will push the other end home a bit further if it needs it.

A more powerful magnet is unlikely to cause any harm, put it on the rear servo rear mounting bolt.

You dont want to be removing any valve block screws unless you really have to, but they dont have spring washers anyway. Look at Eisdielenbiker's picture, that hasn't got them either.

[mcgill]

thank you harvey

[Phil Nottingham]

Actually the sump does not stop the pipes coming adrift as lost second gear once beacuse one end of the dropped enough to cause loss of pressure - just tapped it back in and it stayed there for evermore and no more problems

[harvey]

The sump should stop the pipes coming out, but some of the pipes are different according to the type of sump and valve block fitted, and as with all of these boxes, with the age that they are now, there's been plenty of time for the wrong ones to get fitted along the way.