722.6 sometimes downshifting to 4th and not wanting to upshift

[Steve@Avantgarde]

Sounds like an issue on the valve body or possibly a worn band or clutch pack inside the box

 

[charlysays]

I'll just keep driving it... no way I'm going elbow or even wrist deep into it without any fault codes or knowing it's actually fixable. I guess it'll either get worse or stay the same or just possibly go away. At the moment its not done it for a couple of days.
It always does it after coasting. I come to the bottom of the long hill coasting or semi coasting at 60mph, brake down to 35 for the bend, then when I put my foot back on the juice at the bottom its gone down into 3rd (would've normally been in 4th) then hangs on to all gears a bit too long, then behaves fine.
Box works fine under kickdown from standstill or overtaking too.

 

[charlysays]

It's back... drove about 10 miles in 4th gear doing 3.5k rpm last night. Atleast overtaking didn't require a down shift lol. Did 25 miles in it today and it was faultless!
I'm noticing a pattern in that it does it when ambient temps are below 10C.
Checked the fluid again today and it's just over the top mark at 80C.
I think I'll drain a bit more off and put a can of that Lucas stop leak/slip in it as an experiment. Nothing to loose.
I think the rear seal where the prop flange is is oozing slowly. Never any drips on the drive (undertray is not fitted) but it's damp there.
Will keep driving and think about having the codes read again if I can provoke it sufficently.
Shifts are still normal and no slipping, just a tad inappropriate and hesitant when it plays up.

 

[om613]

Worth swapping out with my old car's valve body and plate....?

 

[charlysays]

I'm loath to butcher a perfectly good auto box in a running car for what is basically guess work though
I felt bad enough robbing a DV spring out of my donor cars perfectly good I.P when I dropped one into the black hole by the I.P when doing the DVs on this car in October lol.
Seeing as it's very much intermittent and usually happens in sub 10c temps I'd guess it does point to a sticking valve. Maybe the 3yr lay up before October had something to do with it. If a clutch pack was toast or there was a split in a drum you'd expect a consistent issue including slipping?
The local factors has a bottle of lucas transmission fix so I'll drain off 750ml tonight and chuck it in. Certainly doesn't seem like it'll do any harm.
I used some of that Xado EX120 in a manky auto box in my briefly owned Subaru legacy in NZ and it made a huge difference.

 

[charlysays]

Bit of an update. Decided to drain another 750ml out and replenish with a bottle of Lucas transmission fix.
Had a good look at the fluid this time and there were no particles and it smelt normal. Was a dark red with a hint of brown, which I remember being "normal" for my other 722.6.

I've done several hundred miles now including a few cold starts in sub 10 degree temps and its been behaving itself. Upshifts are a lot smoother and down shifts are firmer.

 

[charlysays]

Did a 500+ mile round trip to Doncaster and back at the weekend fault free (well, apart from the exhaust starting to disintegrate on the home stretch). Will update again if/ when it dies!

 

[charlysays]

because I'm anal I'll do another update. Gearbox pulled its "I'm not going into 5th" thing again some time in March (after about 20k miles on new atf and lucas trans fix) and I quickly changed the ATF again with fuches titan 4134 and put in another bottle of lucas transmission fix. Been fine since. It's been fine now for another 15k miles. I think the total mileage since this issue first happened is about 35k miles now. Goes to show additives can keep things going and are always worth a try (providing no reports on internet of them making anything worse) before buying parts and dismantling especially when there were no codes logged as with this weird fault.

 

[Wighty]

because I'm anal I'll do another update. Gearbox pulled its "I'm not going into 5th" thing again some time in March (after about 20k miles on new atf and lucas trans fix) and I quickly changed the ATF again with fuches titan 4134 and put in another bottle of lucas transmission fix. Been fine since. It's been fine now for another 15k miles. I think the total mileage since this issue first happened is about 35k miles now. Goes to show additives can keep things going and are always worth a try (providing no reports on internet of them making anything worse) before buying parts and dismantling especially when there were no codes logged as with this weird fault.

That's an interesting update buddy . Thanks . Long may it keep working

 

[om613]

That wasn't my old car, was it mate?