Hello all,
Another little quirk with my new toy, If i accelerate lightly(?) I get all the gears smooth as you like but if I accelerate with a bit of urgency then it appears to hang between I think 2nd and 3rd as if the throttle has backed off, stumbles a bit then continues to change as normal. this has also happened a few times if I kick down (from 4-3 I think). I have tried the adaptive learning set up for the gearbox but it does not appear to have done anything. I have checked the gearbox oil level and i think it is a little on the full side could this be the problem?.
I have cleaned the TB and electrical terminals as well just in case.
Have trawled the net and even MB forums but no joy.
Any ideas out there please
Before you ask 1999-2000 XKR 115,000 replacement box at 75,000ish

 

What! nobody has had this problem my car must be uniqe

 

rrosscoe - This may be a long shot, but I'm thinking it might be your traction control. On my XK8, if I jump on it till the tires break loose, the traction control thottles the engine back and it feels a lot like what you are describing. With the power of an XKR, it may be that simple - it's just doing its job. This would be even more likely to happen if your rear tires are worn. I'm not sure how you check it out because if you turn off the traction control and stomp it, you'll just smoke 'em. Maybe you could try it on wet pavement and see if it happens at less than full throttle as the tires break loose.

Good luck.

 

Rroscoe,

Does the transmission make a whooping sound when it kicks down uinder heavy acceleration? There may be some moisture in the transmission fluid. The Dealer had an additive that solved this for me but concern on the dreaded "whoop chirp" expressed by others caused enough concern for me to pick up an aftermarket warranty.

I am not sure of availability of the aftermarket warranty in the UK but it cost about $3,800 US for the warranty and although transmission is still fine, it has covered at about $5,000 to $6,000 in miscellaneous.

Back to the transmission, it took a second re-set of the transmission to re-learn shifts after moisture was out before it settled down. In my case moisture probably entered via cracked connector pipe.

If it is the dynamic stability control (DSC) as mentioned above (gives a "bucking bronco" effect - lots of fun in a high speed corner) the "DSC" warning light with orange flasher will come on. Remarkable thing, usually not the time you want to take your eyes off the road, use an assistant that does not mind putting their head in your lap to get a good look. If you are getting this warning, switch off DSC when you want to play but be careful, it is there for a reason.

Good luck, even if it is not a DSC issue it still may be solved with an additive.

Regards,
Steven

 

Thanks guys, i will try with the traction off when i get the chance as car not available at moment, I cannot remember it making any funny noises whilst struggling to make its mind up as to what gear i need but will listen closely as soon as I get a chance.
cheers for now

rrosscoe

 

Does it happen on every 2-3 shift with heavy throttle? Does it make a difference you you are going straight as opposed to a curve?

 

I agree the traction control theory is worth investigating.

But the whoop noise is a characteristic of the 2003 and later 6 speed ZF transmission, not the 5 speed Mercedes transmission on a 2000 XKR.

 

Most modern auto trannies are sensitive to overfilling. Get the level right and see if that fixes it. When they are too full, the fluid foams and does not pump like fluid, lowering shift and piston pressures and causing hesitation. Do it quick, foamy fluid does not lubricate well either.

 

Ref Andy 94sc

I have only tried flooring it in a relativley straight line, a slight turn in the road but not a tight corner not enough to get the computers shutting everthing down and it does as far as I remember do it every time i try and either kick down or accelerate whilst in motion 45-60 mph ish .As i said in my original post if I pull away from standstill it does not have the same problem and it will pull cleanly as long as you have your foot in the pedel, seems like it does not like changing down, or doesn't like sudden changes to the throttle pedal.

oldmots,
you may have a point as mentioned I dipped the gearbox (with my own dipstick which may give the wrong level i must admit) and it appeared to be above the recomended level so it may be too much oil, will try and obtain the correct dipstick and try again, problem is I haven't access to the car at moment so will have to wait GRRR
Thanks for the input guys

 

It also does not transfer heat very well either. I was told that overfilling this trans can cook it faster than having it low.

I was asking about the curves, because I am pretty sure this trans will not shift under heavy throttle if you are in a turn, in order to keep from upsetting the suspension.

 

Well I have managed to have a drive in the beast at last, the symtoms are as stated before, from a start through all the gears it appears to do as advertised but when demanding excceleration on the move either with kick down or not it still cannot decide which gear to give me also i tried with trac off and it is the same, in S it is a bit quicker deciding but still bogs down before changing.
It seems that as it is supposed to back off on the power to give a smooth gearchange it is over compensating and taking too long to restore the power request to the engine, does this 722 box have a software upgrade available? or a hard reset to put it back to default (i have tried the disconnected battery and shorting the cables route to no avail) the more i check it, it seems to point to the gearbox control unit but how do I check it out?.
wierd eh

 

SORTED !
After a lot of checking this and that I am pretty sure I have solved the problem, (not wanting to tempt fate that is) a while ago whilst checking / cleaning MAS and throttle body upon replacing the air trunking to the trottle body I had a closer look and thought " I am sure that that should be a tighter fit" so wrapped some insulation tape around outside to build up the diameter to give a tighter fit which it did, any way to cut a longer story short I drove it like this for a while and it was like driving a different car, gone were the hesitation on kick down and between changes and it had found some more oomph.
So i ordered a new trunking and seals (the trunking was getting a bit hard didnt want it to split) and now she drives like she always should have done, I have had no recurring problems in the last couple of months since i did it so it would appear that it is now SORTED
thank you all for suggestions, hope this is of help to somebody else.

regards
rrosscoe

 

Thanks for posting the successful conclusion to this issue.

I've changed the thread title to add 'RESOLVED'.

Graham

 

Thanks GGG for changing the title. That really helps us keep track of all these little issues.

Thanks again.