Autobox woes...please help :(

[Paulifa1]

Hi all,

A few weeks ago now I changed the reverse piston in my V6 2.5 Autobox following symptoms of what I suspected to be its early failure. The car was dropping out of gear and revving up in 4th and 5th gear, but only occasionally and only after driving several miles. Easing off on the throttle when this happened would coax it back into gear.

When I did the job, I couldn't actually find a definitive crack in the old piston, there was what might have been an extremely slight crack, but it could also have been a casting mark, as there were many of those present. Anyway, I put it down to being early on in the failure and the crack being too slight for me to see...

I re-assembled with new frictions as well as the new piston, although there was almost no visible wear to the old frictions and all the steels looked like new. Since then and until today the box has been performing perfectly. It's now started to drop out of 5th again for no good reason.:duh: To further elaborate, as an example I am driving along at a constant 60 mph, I accelerate moderately, or start up an incline and 5th gear disengages, but doesn't change down or anything, the revs just increase and backing off the throttle causes it to re-engage.

So it looks like it was something else. I did test all the solenoids before doing the piston and they were all in spec.

The box performs like brand new and is as smooth as silk up and down, apart from this fault, so any ideas? :shrug:

Further info if it's any use, 54K on the box, no metallic particles or grey sludge at all were present when I did the piston, no visible wear to any bands or friction material, even the RPM sensor had none of the usual metallic sludge build up on it. It also has the correct N402 spec. oil in it.

PS (please, please, please don't tell me the torque converter is knackered :mad:)

[SD1too]

Check again that your fluid level is correct Paul.

Also, have you checked the solenoids' DC resistance?

Simon

[Paulifa1]

Thanks for the reply Simon,

I'm pretty sure the level is correct, it was slightly over filled then, the excess drained via the level plug with the car idling, so should be fine.

I did check the solenoids resistance values and they were within the spec. given on the info page on here. Do you know of other tests I might consider for these at all?

I might arrange to get it over to Trikey next week and see what a T4 says :shrug:

[Paulifa1]

Thought I better finish this story!

I unplugged all the round transmission control loom sockets blew them all out with an airline and plugged/unplugged & re-plugged them together a few times. Although there was apparently no corrosion or dirt on any of the pins, there must have been an intermittent connection somewhere as I've since driven over 100 miles with no further problems at all :)

[Greeners]

Thought I better finish this story!

I unplugged all the round transmission control loom sockets blew them all out with an airline and plugged/unplugged & re-plugged them together a few times. Although there was apparently no corrosion or dirt on any of the pins, there must have been an intermittent connection somewhere as I've since driven over 100 miles with no further problems at all :)

thanks for the update

[johnnyb44]

That's great news. Well done to you.

[mh007]

Thought I better finish this story!

I unplugged all the round transmission control loom sockets blew them all out with an airline and plugged/unplugged & re-plugged them together a few times. Although there was apparently no corrosion or dirt on any of the pins, there must have been an intermittent connection somewhere as I've since driven over 100 miles with no further problems at all :)

That is good news!

I do wonder though............could this have been your original problem?

The reverse piston ends up with a fracture rather than a definite crack, that is, it can indeed look like a casting mark!!

[roverbarmy]

I sometimes wonder how many auto boxed cars have been scrapped due to similar problems being mis-diagnosed as not worth repairing?:shrug: I've also seen lots of smart looking Jags with low miles in local scrap yards.
Mike

[James.uk]

Before I joined this club, 2008. I owned a White 75 Diesel auto, it had a nasty habit of refusing to change up beyond 3rd gear, failing to start, and showing EP on the screen.

Most of the time the car drove well as the gearbox was only 4 months old!! Fitted by an auto shop with 3 year garentee..

But.. Despite multiple visits to the garage they failed to find anything wrong with the car! So I loaned them the car for a week, next day they called and said the car was back with the autobox supplier, so I assume they went out in it and it broke down... heh heh.. :devil:

Anyway, long story short, they took the car back and reimbursed me.

BUT.. had I known MarinaBrian, Jules, BigRuss, etc etc, I am certain they could have fixed that car, as I have always believed the car had an elec fault, not a mechanical one... :shrug:

Sadly that car went to the scrap yard as they failed to fix it.. ..

[SD1too]

I sometimes wonder how many auto boxed cars have been scrapped due to similar problems being mis-diagnosed as not worth repairing?
A lot Mike, I would say. In my experience the specialist trade has only one treatment for automatic transmissions: recondition them and relieve the customer of something like £1,700. As an alternative, this club is providing a unique and valuable service to those with DIY skills.

Simon

[roverbarmy]

A lot Mike, I would say. In my experience the specialist trade has only one treatment for automatic transmissions: recondition them and relieve the customer of something like £1,700. As an alternative, this club is providing a unique and valuable service to those with DIY skills.

Simon
My experience with auto boxes goes back to those from the 1970/80's. They were mainly mechanical in operation and only seemed to fail if the transmission fluid became dirty or leaked. The brake bands could be adjusted then but it seems that the modern auto box has gone the way of the modern engine (ECU says Yes - or No!).:duh: If you cleaned the filters, changed the fluid and kept an eye open for any leaks, they were extremely reliable in my experience.
Mike

[SD1too]

My experience with auto boxes goes back to those from the 1970/80's. They were mainly mechanical in operation and only seemed to fail if the transmission fluid became dirty or leaked.
Hi Mike,

Yes, I've got one of those in my SD1; a GM 180 with 3 speeds (well you don't need any more than that with the Rover V8 engine's smooth and extensive torque delivery). It's dripped fluid ever since I've had the car but has never failed, and you're right, it's completely mechanical.

To be fair to the JATCo though, the reverse piston problem was an unforseen defect which was addressed and the solenoid trouble is to be expected. Electrics and the hostile automotive environment don't mix terribly well do they. :} And the ECU controlled change quality is a huge improvement over the mechanical system.

Simon