QuestionQUESTION: Hey guys, I've got a seemingly very strange problem with my transmission. I've called around to everyone I can think of, visited forums to ask my question, etc. So far nobody seems to have any idea, so I'm hopeful that maybe I can get an answer here from someone who has possibly seen this before.
My problem is this: when cold the transmission works perfectly as far as I can tell then, when it warms up (maybe 3 to 5 miles) it suddenly will lock into the highest gear selected when in drive it sticks in 4th gear when in 3rd does the same thing as if it is in manual mode only it is in high range and does this in both sport mode and with sport mode off. At first I thought it just wasn't kicking down, then later realized that it was not only missing kickdown, it also doesn't seem to go into freewheel when I let off the throttle. It stays right in fourth gear all the way down to about 30 mph or just under 1500 rpm. Then you can feel it release and freewheel, at this point it will kick down and work semi-normal until accelerated back up to about 35 or 40 mph, then as soon as you let off the gas, it locks right back into highest gear selected. All 4 gears do exist and work, also they shift fine until warmed up. Please, if anyone has any idea where to even start on this problem any information would be greatly appreciated. Thanks in advance.
-Graham
I almost forgot to mention, there is absolutely no check engine light, no stored codes that I can find. Thanks again.
ANSWER: There is probably fine debris clogging the valve body, causing it to jam. If so, you'll need a new one. If there is debrid you need to look at the source, which is most likely clutches that are failing from a more common cause. The net result is a runn gearbox overhaul with a valve body. In the USA that would be a $4k job, at the higher end of transmission overhauls
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QUESTION: Thank you for your answer, I am just wondering why the trans. works completely normal when cold, then has no freewheel or kickdown after it warms up? Is it one of those things where the debris moves out of the way as it sits and then gets sucked back up into the valve body after running for a short time? If so, could I remove and clean the valve body or does the transmission need to come out to do that? Also, there is absolutely no slipping at all, is this normal if the clutches are indeed being destroyed for some reason or another? Also, I changed the fluid recently and it wasn't very dirty at all. It was actually cleaner than most transmissions I've done. The only thing I didn't do at the time was change the filter because whoever did it last broke one of the spacer blocks and I didn't want to get stuck with the pan off and no way to get it back together. Anyway, do you think that changing the filter may help at all or is this going to have no effect at all being that the debris is already deeper in the transmission?
I am also wondering why the transmission seems to drop into freewheel when it gets down to around 1,500 rpm or so? Is this perhaps the point at which the pressure in the transmission drops off and releases the debris?
Sorry if I seem to need a lot of information all in one question about one problem, I'm just wondering if I should attempt to clean the transmission up and maybe replace just what's needed or if I should just go ahead and replace the whole thing?
Well, thanks again. Any and all information is appreciated more than I can tell you.
p.s.-I've read some of your info. on blogspot, I must say I am more than impressed with the repairs I read about and the wealth of brilliant knowledge concerning high-end vehicles and their problems and fixes. Keep up the great work!!!
AnswerI doubt is debris is being released, as you say, which the vehicle is driving. Rather, I suspect debris has clogged something in teh valve body. In my experience, when that happens, you need a new valve body because cleaning does not work. You can buy parts from Erikksson Industries in CT; they are the New England service agents for ZF. Perhaps you should call them and describe this problem; see what they say. They are who I'd send your transmission to if it were in our shop.
