Disco Auto Reverse Selection

[Boydie]

I wonder if anyone can shed any light on a recent problem I've experienced in my 300TDi / ZF Disco.

On occasion it wont select reverse, if I shuffle between any of the drive gears and back to reverse after a short while it clicks in, but this can be a hassle if I'm holding up traffic while reverse parking :-(

I've taken out the "isolation/reverse light switch" and checked it out and it seems to be operating correctly and the plunger seems to be free and the gear selection arms dont appear to be damaged or bent in any way due to regular off road adventures so I'm kind of stumped and any advise or even better, rectification solutions from other owners prior experience will be gratefully recieved.

[Boydie]

Hey Guys and Girls,

I find it hard to believe that no-one out there in Disco / Defender land has'nt had this experience. Can nobody give me any hints or clues. I'm loath the replace the switch as they are around AUD $250.00 - huge cost for a small plunger switch with two sets of contacts, N/O; N/C.

The normally closed set power the ignition circuit limiting starting to Neutral or Park, the Normally Open switch power the reversing lights.

Boydie

[Pete Attryde]

Check the oil level in the box and make sure that the gear selector arm and cable are free and moving far enough.

I doubt the switch will have anything to do with the issue as all it does is switch the reverse lights on and stop the engine from starting in anything but N and P.

HTH

Pete

[Range Rover Blues]

He's right, the inhibit switch has no effect on the operation of the gearbox.

Check the adjustement of the selector, if it's not correct it can damage the 'box.

Drop the oil and have a look at it, if it's not clean and red you need to know why.

If the box is full of crud then a new dose of oil could make things worse, it is a detergeant oil and will lift any dirt and carry it into the governor,I can only suggest several changes of oil in quick succession and a new filter in the bottom of the 'box.

[Boydie]

Thanks for that, I must admit I thought the switch was a long shot but auto boxes are a bit of a mystery to me but I'm loath to change it for a R380 as the ZF is generally a more reliable unit (if its working correctly) and its certainly less harsh on the drive train.

Just checked by draining a little and the oil is reasonably clean but the level is slightly over full, I'll drop the pan and replace the filter and new oil this coming Saturday 19/11/2011 and check on the selector arm report back to you

[Pete Attryde]

Without intending to sound patronising, you do know that you need to have the engine running and then cycle the through the gears before checking the level with the shifter in neutral, other wise the level will appear to be high.

Pete.

[Range Rover Blues]

Noy sure what happens if you have too much oil, other than blowing some seals.

I've heard of autoboxs only having reverse, but not having it is not common.

Could be it's a sticky valve too, so new oil might improve things slowly.

Just guesses though.

[Boydie]

Yeah Pete, no, not patronising but yes I knew about having the engine idling and the lever in Neutral and after switching fron Drive to Neutral for 2-3 movements to ensure that the oil was fully circulated.

My guess is that the govenor is full of crud, even though the oil looks fairly clear but the box has only done 256,000 kilometers and thats nothing for this particulat series and type of auto ZF however it's become very sluggish of late and reluctant to engage first from stationary, staying in second until initial movement and then it pops back into first and off it goes. Once moving its a joy and far more economical that the R380, easier on the transmission and works well with the cruise control.

My plan is therefore to fit a new filter, switch to Synthetic ATF and change the oil and filter at least three times before we set off on out after Christmas 6000 kilometer trip to lake Eyre and the Birdsville Track into the Simpson Desert to fully flush the box.

[Range Rover Blues]

You might have to take the governow out to get it clean, i understand it can be done with the gearbox in place (T box off) but i havn't done it myself.

[Boydie]

Thanks for that RRB,

Well, I today drained as much of the old oil out as I could, about 4 litres (out of a claimed 7.5 litres total !! ) and replaced the filter taking great care to ensure that the two "O" rings were correctly located and were sealing -- just how you tell this is beyond me but I'm informed that if the top one isnt right the pump can suck air rather than oil and that this can lead to all sorts of problems.

The old oil didnt seem to be too dirty, however although, from what I assume was a date stamp on the filter caseing the filter seems to indicate that its been in there for a while, as in over 5 years! or it could have been recently installed before I purchased the Disco in 2009 but had been sitting on a dealers spares shelf for a long time, who knows? Do dealers rotate their stock or can the old units get constantly pushed to the back ???

The external faces of the filter had very thin smear of black carbon like deposit on them but the sump was clean(ish), again with this micro thin layer of carbon and there wasnt any metalic forign objects adhered to the magnet that was sitting in the pan adjacent to the drain plug. Looking up the inside of the box looked very clean to my inexperienced eye.

With the new filter installed I refilled the box with 100% pure synthetic oil so now I have a 50/50 mix of the original mineral detergent ATF and new Synthetic.

On a posative note so far I've only traveled around 50 kilometers but the operation of the box does seem to have improved .

I'll run it for a couple of weeks and drop the oil (again) and refill (again) with the synthetic fluid, this should equate to a 75/25 mix of synthetic/mineral and before we set off for our post Christmas adventure expedition into the Simpson Desert to tackle the famous Birdsville Track -- 700 kilometers of sand dunes and creeks and the Lake Eyre salt lake -- I'll again change the filter and replace the oil, by this time the oil should be almost 100% synthetic.

If it's still pissing me off on my return I'll drop it out and have it overhauled but this seems to be a oddity as these ZF boxes should run for well over 400,000 kilometers without any major attension other than regular oil and filter changes and kick-down adjustments if the cable gets stretched due to excessive heavy peddle use, as in city traffic, or so ZF tell me.

They could only surmise that possibly the "O" ring seals on the govenor "could" be worn but they think that this would be unusual given it has only done 265,000 kilometers, again their advise was to try the synthetic solution I've described before stripping the box down. Incidentally the gearbox box oil pump pressure was good and well within their acceptable tollerance when they tested it with their pressure guage so I'm really non the wiser but learning fast.

Any further comments and sugestions from any of you would be well appreciated.

[Range Rover Blues]

My ZF went after a recorded 65,000miles. The black deposit is normal, it's the remains of the worn clutches, sounds like it;s had regular oil but not a filter.

You can never empty the torque converter, even with it in your hands you only get a litre or so out, hence you can't replace the oil completely which is a pain. I vaguely remember a Capri I had was supposed to have one, but as it used more fuel than a V8 RRC I sold it before getting too serious with the servicing.

[Boydie]

My understanding is that the torque converter will never be the problem, all it is a turbo clutch -- unless the seal goes in which case you have a severe case of the transmission fluids leaking from the bell housing.

Is that correct and or can anyone add to this?

[Range Rover Blues]

The torque converter has a number of parts that can fail with use. It has 3 elements inside, the outer is the impeller or pump, the inner which drives the gearbox and the stator ring, a static set fo vanes that redirent the fluid as it circulates, these make the TC more efficient than a simple fluid coupling.

he staor is located on a one-way sprag clutch, these can fail.

Also the TC has a lock up clutch, these apparfnelty are a common failure with big engines.

Also, if there is crud in the gearboc from a failure the depoists get into the TC and can't be cleaned out, rendering it usefless. A TC from a knackered box can then ruin a good gearbox.

Anyway, the problem with changing oil is that often new oil is more detergeant than the old oil and starts to lift deposited detritus, moving it into the governor where it can do damage. What you want is to be able to flush the gearbox out and remove said detritus, you can do this completedly and in the worst case you flush the bits inside the TC where they don't come out again.

[Boydie]

Happy Days !!! A local (Sydney Australia) lubrication company, NULON has an automatic transmission additive that is designed to keep the carbon and other deposits in suspension so that they/it either gets caught and held in the micro fine mesh filter or dumped during the subsequent oil change.

It seems to be working as the lube in the box has gone from light bright red to dark redish brown in less than 500 kilometers, the gears are changing crisper and the original reverse selection problem seems to be resolved.

I'll dump the oil in two weeks, replace the filter and re-fill with full synthetic and see how it goes. It seems to me that the original general diagnosis of regular oil changes having taken place but not the filter was correct. Sludge has possibly therefore been allowed to accumulate sticking valves and generally gumming up the works.

Hopefully by taking the action of switching to full Synthetic oil and dumping said oil several times along with 2 filter changes and the Nulon additive I've managed to disolve and remove most of the sludge and increase the expected life of the box before I'm complelled to have it stripped and overhauled.

[Range Rover Blues]

I'd like to know how you get on (though I think it would have been too late for mine) and do you have details of the stuff you bought.

Then I need to see if it's available in Europe.

[Boydie]

I spoke to Nulon today on your behalf, they dont export and dont seem inclined to consider this venture given their limited production capacity and the existing AUD to USD, Stirling and Euro exchange rate, for example 4 litres of their synthetic oil is AUD $78.00 add to that export costs etc. etc. etc. and !!!!!!

The engineer I spoke to defined my problem as kindly as he was able as me being a clown / idiot / moron / imbecile for draining the transmission oil while the engine was in pieces and leaving the box "dry" all I did was to exacerbate the problem of the carbon sludge adhereing to the internals and gumming up the works. Had I know all this I should have overfilled it with a cheap ATF oil and then dumped it as a "flushing wash" before removing the sump, cleaning it, replacing the filter and then refilling it with synthetic before starting the engine.

The same result is apparently is likely to occur if the vehicle has been sitting for an extended period, say over a couple of months over winter or whenever you dont use it as the carbon sludge will decant from the sump oil and into the bottom of gearbox sump where the pump pick-up will suck it up when it next gets used pumping the goo in concentrated form back into the inner works of the box ....... the moral to this tale of woe of mine being if you dont use it your LR for a while and it's fairly high mileage drain and replce the oil before you restart it, once the engine has been started its too late, the sludge has been circulated! The obvious alternative is simple, run the engine for an hour or so every week.

On the posative side, their addative, along with several very expensive oil and filter changes will rectify my problem as the synthetic solvent oil will remove the sludge and when discarded should conversely resolve the problem. Its still cheaper than the cost of a reconned ZF box

I'll let you know how I get on.

[Les Brock]

Interesting,

So what happens when your building over a projected time scale ?

My ZF22 has been drained down and had new filters etc fitted ready for the big start up (some time TBC), so do I leave it empty or fill it back up again ? bearing in mind its not likely to start for some time lol...

Recomendations.....

[Boydie]

Les,

I guess you have to consider the options, If you are going to have the box sitting there unused for a period of time as mine was (3 months) then my advice would be, again based on my experience, fill it with a low cost ATF and drain and change said cheapie oil before start up. Alternativly remove the govenor and flush it with a non corrosive cleaner. If my experience is anything to go by, and if I had hindsight I would remove the new filter, replace the sump pan and fill it with cheap ATF up to the spout and then drain it and refit the filter just prior to starting the engine.

On a further happy note my ZF22 is improving every day and is becoming a delight to drive with crisp down changes with the engine reving out to 3500 in all 3 lower gears.

[Les Brock]

Thanks for the reply,

Hmm....Removing the Govenor, sounds complicated lol

Removing the sump, filter etc easy as.....how easy/difficult is removing the Govenor

Bearing in mind its been sat for nearly a year so far, just dont want any probs when I do start it, anything to prevent a problem I'm happy to do !

Regards

Les

[Boydie]

Removing the govenor really requires the removal of the box but if you enjoy a struggle I am informed it can be done in situe but the Transfer Box needs to be removed first, in other words it would be just as easy to drop the ZF and strip it down, the easier solution would be just to remove the filter and fill the entire box up with cheap ATF and leave it fully flooded until you are finished and ready to restart the engine.