Reason for the trans "thump" according to erricson engineering (and doesn't a new trans feel great)

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Apr 10, 2008 | 02:49 PM

#11

CalG

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Understanding

Z....

Help me know.

Did the rebuild NOT correct the "Thump" at all?

Your explaination of the VB causing the problem would suggest that even a "fresh" tranny with the old VB would show the similar performance issues.

Any information regarding the "hunt". The latest report from my wife, The daily driver, After replacing the VB in our 99, with one from a later model. "The tachometer variation is between 100-200RPM, and only when slightly accelerating or when pulling a slight hill with constant throttle. Same as the original VB really, just much reduced in amplitude.

I do need to investigate the old VB sitting on the work bench. With warmer weather and longer days, Perhaps there will be opportunity.

Please tell!

Cal

Apr 10, 2008 | 02:50 PM

#12

CalG

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Re: who did your rebuild?

Angus

Ericsson Industries is in CT. IIRC.

Authorized ZF repair facility.

Z.. Were you satisfied with the service?

Cal

Apr 10, 2008 | 03:03 PM

#13

Zaphod A8

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I didn't have much of a thump (other than the big one when the clutch went) before the rebuild...

and there is still a little bit of a thump on the 5-4 downshift under power after the rebuild. As I understand it the new internals from a rebuild would make no difference on the thump unless you do a new valve body too. I say new valve body because the housing seems to wear faster than the internal valves themselves. As was explained to me, the wear in the housing causes more fluid to flow than designed, and therefore higher pressure when shifting leading to a thump. You can replace the internals all day and that won't effect the wear in the aluminum housing.

I don't know about the hunt, though I would imagine that would be related to the torque converter not locking more than anything. Especialy with such slight variations. They did do the TC with a rebuilt one that has been improved a bit from stock. Apparently these ericson guys down in southern new england are quite good with the ZF and have been improving techniques over the years.

It was suggested that I replace the VB before next winter, but other than that things are smooth as silk.

Apr 10, 2008 | 03:08 PM

#14

Zaphod A8

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Local shop (imported car center) did the work with support and parts from Ericsson.

They did a good job, almost spot on to the original estimate. Seems they have done more than a few of the pre-facelift cars and are quite familiar with the intimate details of our lovely transmissions. Paul is the foreman there and while not as versed in modding as our other Pauls, is very knowledgeable about fixing stock work on the A8s.

Apr 10, 2008 | 03:09 PM

#15

Zaphod A8

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Other than the slight (ok, excruciating) pain in my wallet, it is quite nice!

Apr 10, 2008 | 03:12 PM

#16

Zaphod A8

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well whenever the engine is spinning, doesn't that spin the TC and pump fluid, therefore warming it?

the guys at the shop talked about how the cold weather seemed to eat through the transmissions faster because it is so much thicker when cold ...

haven't tested it, but makes sence with other hydraulic fluids I have messed with ...