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Problems with autobox on 200Tdi Disco (slipping third, stuck third to fourth change, slipping reverse)

People Hi again,

The autobox on the camel (a 200Tdi 1993 evented Discovery converted to autobox) has started developing a problem with its high gears.

It appears that the four gear is reluctant to engage and that third gear is stuck or slipping.

The vehicle runs nicely at fourth gear with around 3000 rpm at 120 Kph. But after a while third gear changes by slipping downwards at the rpm range and the engine runs at 4000 rpm at 100 Kph with the gearbox not wishing to change up to fourth gear.

It also has a general feel like a manual gearbox with a very worn clutch.

Gearchange from first to second and second to third is OK.

When the "slipping" and stuck gearchange from third to fourth (not happening at all that is) is happening the car also has problems with its reverse gear. Meaning that when I stop and wish to reverse the engine revs a lot for the car to actually move back and it also has the "slipping clutch" feel to it.

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The autobox was struck with a contaminated ATF problem some years ago which led to the ATF burning and also chaffing the friction plates. The ATF was changed three times, an antislip additive was added and it worked nicely for about two years. Then the first gear got stuck (no change to second gear or upwards). Gearbox was removed and checked. Friction plates were found to be OK and a spring in the vavles housing was found to be broken in three pieces. After that the autobox was re-installed with almost no problems apart from a reluctance to engage first gear immediately when very cold and a somewhat bumpy change from first to second gear.

I have bought a nice secondhand autobox from a 300Tdi Discovery (complete with torque converter) so most probably I will be replacing the faulty unit altogether.

But it would be very helpful to know what is the most probably cause for the "slipping" third gear, stuck third to fourth gear change and "slipping" reverse problem (all of them not happening until the car is hot and not happening all the time).

One more thing that was happening was that the kickdown appears to have been engaging very easily. When on fourth gear and at around 130 kph if I pressed the accelerator pedal more ( in order to increase speed) the kickdown would engage and drop down to third gear (with 4500 rpm at the engine). Is this something that can be addressed to by shortening the kickdown cable's travel (effectively increasing the accelerator pedal's travel without engaging kick down) and would this be a reason why the third to fourth gearchange has started to malfunction and the third gear friction plates most probably got worn out?

Sorry for the big posting and lots of questions but autoboxes are unknown land and your input is always appreciated and extremely helpful into getting into grips with things.

Take care and happy New Year. Pantelis

Reply to
Pantelis Giamarellos
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On or around Sat, 6 Jan 2007 11:14:19 +0200, "Pantelis Giamarellos" enlightened us thusly:

I bet that's one of the clutches, but not "A". Odd, I thought it was in the book, must be in Rave.

hmmm. Symptom 9: no 4th gear in "D"

4th-3rd downshift valve stuck 3rd-4th upshift valve stuck Clutch Brake 4

trouble is the LR book which has a power flow chart for each gear has numbers for all the clutches and brakes, whereas other people use letters.

However, I can't see a clutch/brake which is common to 4th and R and yet is not used in other gears. ... hangon yes I can: clutch 5 in the power flow charts applies to 3rd, 4th and R, but not to 1 and 2.

5 is the second clutch from the front of the box, which is I think the "B" clutch. Anybody's guess where clutch brake 4 is...

However,if you've got to the point where clutches are slipping, it's rebuild time... or replace, as you suggest.

Badger is the expert on these... I've no doubt he can confirm or deny.

Reply to
Lord Austin the Ebullient of Happy Bottomshire

Can one repair their own autobox, out of interest ? Haynes turned gearbox repair into a region where here be dragons years ago.

Steve

Reply to
steve Taylor

It's possible for the "A" clutch to wear quite badly but still drive ok in the lower gears, just slipping in the higher gears same as a normal worn clutch on a manual box.

"C" or "C1", 4th from the front I think, I'd need to go and dig out the books to confirm.

Indeed. Sounds like it is generally well worn. The "hanging in 1st" symptom is indicative of the governor unit in the rear of the 'box sticking, no doubt due to some disturbed crud or debris while all the flushing was being carried out - it's virtually impossible to get all the wear particles out of the 'box just by flushing alone.

Thanks Austin, I wouldn't claim to be an expert though, just a good working knowledge and a fair bit of stripping/rebuilding experience. Badger.

Reply to
Badger

I'd have thought you would have a fairly good chance of fixing it! (and if not we can laugh at you when you have bits left over and it doesnt work afterwards and the question will be answered! ;-) )

Reply to
Tom Woods

Badger and Austin thanks for your input and replies.

It appears the car will go to the mechanic to have the autobox, torque converter and transfer box (the autobox came together with a BW) replaced.

Will let you know of how it comes out.

I have also just finished adjusting the kickdown cable so that it allows a bit more travel to the accelerator cable/pedal without the kickdown engaging.

Thanks again. Pantelis

Reply to
Pantelis Giamarellos

No, todays project is the Diff chop / rotate, or there won´t be an article in the 101 magazine.

Steve

Reply to
steve Taylor

On or around Sat, 06 Jan 2007 11:19:17 +0000, steve Taylor enlightened us thusly:

yes, but autos tend to be a bit fussy about cleanliness.

Reply to
Lord Austin the Ebullient of Happy Bottomshire

On or around Sat, 6 Jan 2007 11:25:10 -0000, "Badger" enlightened us thusly:

it's a pity the schematic which relates to the power flow diagrams uses it's own set of numbers which don't appear to be translated into the ABCD etc. which are used in the exploded pictures of the box.

The power flow diagrams are handy as an aid to diagnosing faults.

Reply to
Lord Austin the Ebullient of Happy Bottomshire

Bit drastic!

Where are you at with the Ambi modifications these days?

Lee

Reply to
Dr_D

Waiting for some decent weather ! We´ve got the engine rebuilt, and ready to mount on a rebuilt gearbox.

Steve

Reply to
steve Taylor

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