Rolling start gearbox hiccup?

Hi All,
has anyone experienced a hesitant change down - say on the run up to a roundabout, when slowing, if you go and don't stop, the gearbox hesitates before selecting 1st?
I had a S type Jag with this problem, but this had the later 6HP 6 speed box.
The box had a fluid/ filter change before I got it and normally runs fine, just occasionally this occurs.
Any ideas?
Thanks

Petrol or diesel?

Apologies, thought I should have added this:
2002 4.4 @86000.....

I very occasionally get it on the TD6 with the GM box, but more of a 'slight lumpy' change down to 1st than a 'hesitancy' thing though.
Never worried me TBH, you can't expect an auto box to never have any slight imperfection very occasionally when it comes down to gear changes, TC's locking up etc IMO.

Yes - I had it at about ~75,000 (4.4 V8) , did an oil change that I should have done at 60,000 but was advised not to do (grrrrr), and the problem went away....

An assumption. but I expect that it wasn't a full fluid change. See:

http://www.landyzone.co.uk/lz/f71/zf5hp24-fluid-drain-filter-change-212722.html

For how to do a change - the point is that unless do as (not easy to do on a RR):



...roughly half the fluid is still old after a 'change'. I've just ordered more fluid to do a second change on mine (with someone to change the gears and someone to pump the fluid I'd estimate 2hrs max, tools aside)

Without a full change it takes many half changes to get rid of the sealed for life oil:

Assuming a 50% change:

Change 1 - 50% new 50% old
Change 2 - 75% new 25% old
Change 3 - 87.5% new 12.5% old
Change 4 - 96.77% new 6.25% old


I have heard some people have used Dextron III to do 1-2 'changes' first then finally one with the expensive oil (Mobil ATF LT71141) - the youtube link uses Dextron III to flush....

In conclusion, based on the numbers above one "change" is possibly not enough.


Charlie

Thanks All
Charlie sounds like a plan, I might just drain to flush once and then change the whole lot including the filter and transmission cooler after reading Saints thread. At least that way I can work out if the level is wrong before getting into some serious parts money.
Thanks again.

I wanted to mention one thing. The oil cooler looks very much like a heat exchanger from a boiler.

I have an old Worcester Bosch combi boiler that kept on turning on and off due to a temperature sensor giving a high value. The boiler was written off by a Bosch engineer due to the list of parts that he would replace (I had to fix it else we would have to get a long flue due to new regs - lots of money).

I'd had the heat exchanger replaced a few years back and after some research the temp sensor read high because the energy from the gas was not being transferred to the water quick enough and thus the temp at the exchanger rose above a threshold.....bare with me here!

So, I took the old exchanger and pumped Fernox DS3 acid solution through it. Fernox has an indicator in it that goes green if there is sufficient Ca Carbonate deposits to react with. I carried on flushing until the colour didn't change, bolted it back on and hey presto it stopped cutting out.

My point here is that an acid flush on the heat exchanger could remove any deposits preventing heat exchange. Fernox is nice as you know when you can stop but vinegar would do - just wait for any bubbles to stop or leave it overnight. A solvent could be used on the oil side (white spirit or cellulose thinners).

Add to it that if coolant and / or distilled water has been used any limescale deposits would be low to zero. I can't really see that replacing the heat exchanger is warranted - a clean would do + o ring replacement. Just my two pence worth and I wont be offended if I'm flamed!



If you do replace it I'd actually pay to have the old one picked up so I could take a look as I've only seen pics (I'm not after one for myself!).

Charlie

Hi Charlie,
thats an interesting thought, after all they flush torque converters. I'll have a think about it and see. I'll check the oil level first and replace it if necessary and see if that helps (The cars only done 10000 since the filter was put in). I've been reading that this oil is not red like Dextron 3 but is a tan colour - can anyone verify this, at least that way I've got 1/2 a chance of checking what was put in.

forthbridge said:

Hi Charlie,
...can anyone verify this, at least that way I've got 1/2 a chance of checking what was put in.

Click to expand...

I''m doing mine in an hour or two - will take a photo of the oil - I believe it is TAN.

Thanks Charlie,
know anywhere to get a good price on the LT71141?

Charlie,
ref using Dextron for a cheap flush - this thread except from Bemble See Navigator 16078 thread L322 Gearbox).
"Make sure that you use Esso LT71141 fluid. It costs £29/litre from a Jaguar dealer, about £17/litre from a Land Rover dealer, but I buy it in 20 litre containers for the equivalent of £7/litre. Don't even think about using Dexron as it has a different static-to-dynamic friction characteristic which will wreck the controlled-slip lock up clutch in the torque converter (it has no torsional vibration damper). You must use LT71141.

When you drain the fluid you'll probably only get around half (5 litres) of the fluid out - the rest is retained in the torque converter, oil cooler & valve block.

When you set the fluid level (via the combined filler/level plug) you must do it with the engine running otherwise you'll be more than a litre down on capacity, and the fluid temperature should be 'warm' i.e. at around 40 deg. C."

Ignore the emoticon... where did that come from, it was supposed to be a bracket!

I didn't take a pic as I had a bad day at the office. It is tan and it does have a sweet smell

Oil everywhere, very exon valdeese - I have to work in a busy road which adds to the fun... A political spin would be that I did a flush and the a final fill but in reality I got in a bit of a tizz and drained it again.

First drain: black
2nd: grey

I bought 20L on ebay, price £137 or there abouts. Approx 2/3s used and at least a litre on my back on the road, duly cleared up with sand - what a pillock.

I am generally UNHAPPY that there is no oil dipstick which makes this job so messy!!!!

Charlie

P.s. I followed Saints procedure for the second time. Refill plug was very hard to undo - can't even blame the manufacturer as I did it up last time...

Yes, agreed, the flush with dextron only makes sense to me if you can flush as per that video link - not something I would do with the arrangement on this transmission...

Out of interest, if it could be done as per the video link would you flush with dextron?

I still stink of oil!

I've got to say I've looked at a number of Bembles posts and as he rebuilds them if he advises not to use the stuff, I'm with him.
That transmission seems expensive to play with, I've noticed that 2nd hand they keep their money although I'd think you'll be knocking on the door of a rebuilt unit once you factor in the cost of a 2nd one plus parts?
I'll have a good look into changing the oil at the end of the month, I've got to have a play with the transfer box connector while I'm at it and the P38 wants all the attention at the moment.

forthbridge said:

I've got to say I've looked at a number of Bembles posts and as he rebuilds them if he advises not to use the stuff, I'm with him.

Click to expand...

I understand Bemble is Range Rover Phil and since I really don't understand how an auto gearbox works / hangs together the specified oil it is, thanks for the confirmation.

Charlie

Glad you got the job done, I hope the car benefits from it. If I get some time over the next week I'll check my levels, as I've been through the paperwork that came with the car and it's oil and filter change was proper stuff. Still, I agree that the chance of clearing the fluid will require more than 1 change so I don't think I'll loose much in the long run if it has to be done again.