Transmission trouble 75k miles after refurb. 5HP24

[TriX5]

So, it has been over a decade and the E53 has done 75k miles since my torque converter grenaded and made a refurb of the trans necessary. It was working perfectly since then with two drain and fills done.

About two weeks ago it went in to fail safe mode. It reverses fine and seems to have drive in failsafe but none in 1st/2nd (?) There was plenty of fluid in it, I recovered what came out when I had a look in the pan. The pan has some fuzz on the magnets but nothing out of the ordinary. When I restart the engine it feels like it wants to move but then reverts to failsafe within the first half second.

I am planning in my head how to get the trans out in order to have a look at the internals. Could be an O-ring, an axial needle bearing or some other mechanical problem I guess.

My question is, could this be a problem in the valve body and if so, what am I looking for? The fact that it wants move before going in to failsafe makes me think there is pressure from the VB in first gear and I would be inclined to assume the VB is ok but any insights would be helpful. (Here's hoping RRPhil pitches in as well :-)

It would of course be less work to just pull off the VB but I have sort of resigned myself to the need to pull the trans. Since the E53 is not critical to our needs I can take my time. However, I don't want it blocking my garage while figuring out what's wrong, it would help to have some idea.....

[RRPhil]

Is there any way you can determine whether the forward gear that the transmission is failing safe into is 4th or 5th? This is significant because it tells us if the A-clutch is responsible. The default is 4th gear, but it will failsafe into 5th if the A-clutch is the problem.

When it comes to determining which gear is selected, nominally the driveline is geared at 29.3 mph/1000rpm in 5th and 23.5 mph/1000rpm in 4th but, because the torque converter is open in failsafe mode, it can be tricky getting the driveline balanced so it’s neither driving nor in overrun when taking the engine speed reading at a steady road speed on the level.

Phil

[TriX5]

Thank you so much! To see if S-mode made any difference I tried it and noticed the gear indicator jumps to 5th when it switches to failsafe. Assuming that indication is correct, I'd be looking at the A-clutch then? I am not driving it at all so as not to over-stress the remaining function, but I could try it and verify with the rev counter and speedometer which gear it goes into.

My car is a June '03 build. IIRC, the '03s did not have the cracked A-clutch cage problem. My car saw quite a bit of city traffic up to 100k but more longer distances after that and has not been used for traffic light drag races. So, likely, it is a smaller failed component. (BTW, now at a shade under 170k miles.)

This weekend I am clearing my garage as I just completed a garden shed. The house construction stuff is moving into the shed. My winter tires are moving there as well some of the nine bicycles.......ugh, got to sell some bikes. I'll report back when I have it apart.

[RRPhil]

Yes, your transmission will have the stiffened A-clutch drum as it was manufactured after November 2000, and also the main pressure valve with the 10mm wide land. That’s not to say that these strengthened drums never fail at the snap ring groove, but it is much rarer.









The cause is more likely to be ‘the usual’ axial bearing wear, and subsequent O-ring failure, I would guess.









Phil

[TriX5]

Thanks! Great info, I will print and have it handy when I open it up.