Citroen C5 Knick Sensor & Automatic Transmission

[Mandrake]

Going to ask the stupid question now. I know manufactures recommend certain products/oils but what difference does it make if they don't put in Mobil and choose (for a random example) Castrol instead?

LT71411 is a special formulation made to order for a few ZF gearboxes (by Esso, now bought out by Mobil) including 4HP20 and AL4 and there is no equivalent type from other oil vendors.

If a different oil such as a more common Dexron II or Dexron III is put in the gearbox then the results will be gearbox failure. If you look back through the forum you'll find numerous discussions of "can I substitute oil x instead of LT71411" and the answer is no. The wrong type of oil can and frequently does kill automatic gearboxes, especially these ones.

[myglaren]

Going to ask the stupid question now. I know manufactures recommend certain products/oils but what difference does it make if they don't put in Mobil and choose (for a random example) Castrol instead?

In most cases it probably doesn't make a ha'porth of difference but it has been shown that those boxes that need LT71411 is crucial to the life of them.
There is a superb stripdown and rebuild blog by Jim that demonstrates this, among other things.

[CitroJim]

It "has" to be that oil, there is no alternative since it is specially made for the AL4.

Absolutely correct. The AL4 (and 4HP20 amongst others) use LT71141 and must have nothing else in them at all. Any other ATF, even if it claims to be LT compatible, will shorten the life of the 'box..

LT71141 is made only by Mobil and has absolutely no substitute. It's expensive compared to Dexron but then so is a gearbox rebuild.

This subject has been done to death on here may times.

On a related note, the old ZF 4HP18 used in early XMs must use only the original formulation of Dexron IID, a mineral ATF. Anything else shortens its life - even Dexron III, a semi-synthetic ATF which claims to be backwardly compatible with IID. It isn't and even ZF have gone on the record of saying so.

Golden rule for any automatic - use only the ATF specifically recommended by the manufacturer and absolutely nothing else whatever the sales blurb and pushy salesmen might tell you...

[Smarty2]

Hi Jim, conversation with an auto box rebuilder with 35 years experience.....

It's the internet again..... You have to stop believing everything said on there.
Now,the Esso/Mobil LT71141 can't be mixed with Dexron3, so if it's in a trans and you want to just change the oil you have to use whatever is in there, as there will be at least 3 litres of oil in the converter you won't get out.
On a rebuild we use Dexron 3 in DPO transmissions everytime with no problems at all. This is from the beginning of that trans to now. We were doing transmissions before the internet existed!
Dexron 2 is not compatible with Dexron 3, not in any form, the fellow is correct on that score.

He buys Dexron 3 in bulk, guess if I have my box repaired there I must insist he uses the oil I will have to supply!!

[Mandrake]

Guess I won't be taking my gearbox there then

[Smarty2]

He comes very highly recommended, by a number of people who have used him including my garage and the people who fitted my gas system, Its Penn autos http://www.redvictor1racing.co.uk/index ... ainmenu-34" onclick="window.open(this.href);return false; and the bloke builds transmissions for racing, drag racing. I have no reason to suspect the fellow is a bad rebuilder based on his belief dexron three is the best thing since sliced bread, just will "insist" he uses LT.

[Mandrake]

Even so, the problem is with a fully rebuilt gearbox with no pre-existing wear it might last say 30,000-40,000 on the wrong stuff, but not the 100,000 - 150,000 you might get from the right oil. By that time its out of the comeback period, and accelerated wear due to the wrong oil might be a difficult one to prove...and what happens to the poor shmuck (possibly not the same owner who had the box reconditioned) who then tries to do an oil change with the correct stuff, thus mixing the oils ? Not good...

Regardless of reputation it seems lazy and ill advised to use the wrong oil against manufacturers specifications (note: specifications, not "recommendations") when the correct stuff is still available.

I wonder what Mackie's would have to say about Dexron III going into a 4HP20 or AL4 Jim ?

[Smarty2]

Indeed, I have already put the matey 30,000 miles down the road scenario at his local garage using the specified oil situation and his comeback was he services 90% of his customers boxes, but didnt mention the 10% that don't? despite this though he has no problem with me supplying my own LT, and servicing isn't a problem as my usual garage does that. I'm a bit wary of AT specialists since I lost a wad of cash on my old xm zf box a while back. soo difficult to find someone you can trust these days.
Further to this I'm afraid he isn't inspiring a lot of confidence, his warranty is only 12 months or 12 thousand miles.
Can any kind soul on these forums recommend a specialist at all preferably in the west midlands but not VMTP in cannock, they totally are not on my christmas card list!

[CitroJim]

I wonder what Mackie's would have to say about Dexron III going into a 4HP20 or AL4 Jim ?

Same as I. The manufacturer states that the ZF 4HP20 must use LT71141 and their oil specifications clearly state that and clearly state (if you read it properly) that Dexron of any sort or anything else will not do...

However... That's for ZF 'Boxes. No ambiguity there at all... For Siemens AL4 series 'boxes (known as the DPO on Renaults) there is ambiguity as I believe Renault might recommend Dexron III for the DPO even though PSA recommend LT71141 for the AL4 (same 'box) when fitted to a PSA vehicle...

I've not as exhaustively researched the AL4 situation as I have for the HP20..

Dexron III may be OK in the AL4 but only if that's the ONLY ATF in there and all traces of the old has been removed, which is only possible after a full rebuild and with a new TC. PSA vehicles will have had LT71141 in them originally so that's what must be used in a PSA vehicle.

So, no mixing of ATFs under any circumstances and use only what the manufacturer recommends and nothing else bearing in mind that LT71141 has no substitute and especially not Dexron III

So basically we come back to the original recommendation and statements...

[Smarty2]

Hi Jim, blimey, I'm up and down like a newly weds nightie! This ambiguity with dexron III v LT has made me unsure whether to trust this fella or not?

[Smarty2]

Has anyone here had any experience of these companies? http://www.testransmissions.co.uk/tes-t ... -2008.html" onclick="window.open(this.href);return false; http://www.drivertransmissions.co.uk/index.html" onclick="window.open(this.href);return false;

[CitroJim]

Hi Jim, blimey, I'm up and down like a newly weds nightie! This ambiguity with dexron III v LT has made me unsure whether to trust this fella or not?

indeed. The thing is I'd say it was a fairly safe bet to say an AL4 in a PSA vehicle will be filled with LT. You can easily tell by taking a sample. LT is amber coloured and smells dreadfully awful like a cross between lightly charred toast and cat's pee. Dexron is generally red and a bit sweeter smelling.

LT also feels 'oilier' and a little more viscous than Dexron.

Thing is, if you take it to a dealer can you guarantee he'll refill with LT? I'd not expect a dealer and rebulder of transmissions to worry about extreme long life and another aspect of rebuilders using Dexron is that it is very considerably cheaper in bulk than LT so it helps their profit margins... Perhaps I'm being cynical here?

[Ben82]

Jim, what about the really used stuff? If I recall Simon said his black stuff didnt really smell of anything? (But maybe down to his sense of smell ). Though I'm guessing it would have to have been going for a very long time to warrant a replacement in the first place and then would require an equally long time for really used dexron stuff to be indistinguishable from lt? Guessing also probably a longer period of time than the box would last on dexron?

[CitroJim]

Jim, what about the really used stuff? If I recall Simon said his black stuff didnt really smell of anything? (But maybe down to his sense of smell ).

To me Ben, the older the ATF the worse it smells but that may be me as I have a very acute sense of smell...

[Smarty2]

Hi Jim, I know whats in the box it is definitely LT as I have had the oil changed a couple of times in quick succession, besides my garage is a good one and only gets genuine parts/oils in fact he phoned me up saying the LT costs were pretty high and do I want to continue with a double change? I'm in a quandary with this Penn auto's fella whether to give him a go or not, but having had a look at those two specialists I linked to above they seem to have a bit more nouse about them? particularly with TES and their 18 month unlimited mileage warranty and specialising in AL4's, trouble is its a trek, the Brummy one does a 12 month unlimited mileage and charge £1195 for the job. It may be a case of eenie meenie?