6n1 automatic 'Thumps' into gear on occasion (DPN box)

[pontiff]

Hey all,

This is on behalf of a friend of mine who has a 6n1 automatic. On occasion it will 'thump' into gear when taking off from a standstill. Often it can also happen if you are rolling up to a set of lights for example and you then take off as it goes green and you're still rolling. It's happened to me a few times in his car and it feels like you're being smacked in the back of the head with a sledgehammer, its pretty violent. It just revs like its not in gear and then it suddenly grabs and THUMP! and you're away.

We have changed the transmission fluid in the unit (was not that dirty at all) and its not losing any fluid. The 002 auto control unit has not logged any faults and other than this it drives quite fine, changes gears smoothly, kicks down appropriately and generally behaves itself so i am hoping that its not anything terminal. It can go for days without doing it then it can do it twice in the space of an hour.

Am I right in assuming that if it were fluid based it would happen all the time? Could it be a stuck valve in the body of the trans or something? Has anyone has any experience with such an issue?

TIA :)

[Umai Naa!!]

Sounds terminal.

What oil did you put in, and how much?

[pontiff]

Sounds terminal.

What oil did you put in, and how much?

It was the fully syn VW prescribed stuff, certainly was not cheap. Not sure how much went in, I will ask tomorrow but it would have been the correct amount

[Jmac]

Oil wont help it im afraid, piston seals have gone hard and you are getting pressure bypass till it builds up line pressure then you get the Thump. rebuild im afraid, this problem would have caused loads of trouble with clutches so try and source a good second ( rare) or have it rebuilt
Cheers
Jmac

[pontiff]

Oil wont help it im afraid, piston seals have gone hard and you are getting pressure bypass till it builds up line pressure then you get the Thump. rebuild im afraid, this problem would have caused loads of trouble with clutches so try and source a good second ( rare) or have it rebuilt
Cheers
Jmac

ahhh okay thanks for the info, g. Ireatly appreciated. I am guessing that rebuilds would be rather expensive and while it may be false economy, just getting 2nd hand ones may be just enough to keep the car going until something terminal finally takes it from this world?

[Umai Naa!!]

If you've got a known good at your disposal (and I'd be surprised if you didn't :P), might be worth puting one of them in it, and giving the box a service.

If you need a line on cheap oil and a filter for it, get in touch with Tooley Imports in Sydney. The oil's about $22-ish a litre retail.

[miapolo99]

Hi,
Probably a bit late in replying to this thread but I wanted to wait to see if my attempted fix would work. We had the same thump happen to us after the transplant of the auto (which was like being rear ended by a bus). Out of frustration and having some "Lucas transmission oil" on hand, I added 10ml to case, after a week the thump lessened so I put another 10ml in and after 6 months of driving the thump has 99.9% been eliminated. The purists will probably Kringle at this action but it's worth a try and a lot cheaper than replacin

[pontiff]

Hi,
Probably a bit late in replying to this thread but I wanted to wait to see if my attempted fix would work. We had the same thump happen to us after the transplant of the auto (which was like being rear ended by a bus). Out of frustration and having some "Lucas transmission oil" on hand, I added 10ml to case, after a week the thump lessened so I put another 10ml in and after 6 months of driving the thump has 99.9% been eliminated. The purists will probably Kringle at this action but it's worth a try and a lot cheaper than replacin

thanks for the reply.... I changed the box out for another one but it still sitting at home while i try and work out what the hell to do with it, so if i ever have a need for it, then I will certainly give that a shot because realistically it can't hurt anymore than the box is already :)

[Jmac]

Hi,
Probably a bit late in replying to this thread but I wanted to wait to see if my attempted fix would work. We had the same thump happen to us after the transplant of the auto (which was like being rear ended by a bus). Out of frustration and having some "Lucas transmission oil" on hand, I added 10ml to case, after a week the thump lessened so I put another 10ml in and after 6 months of driving the thump has 99.9% been eliminated. The purists will probably Kringle at this action but it's worth a try and a lot cheaper than replacin
That has seal treatment and what it does is swells the seals, it isn't the big fix though. As long as it holds up all good, the products are good and get spruiked in many Muscle car mags with really old barn find cars