We have to do an emission test on our D2, and being full time 4WD it cant be put on a 2WD dynamometer, so they rev it in park.

I recall reading that the ZF transmission in our trucks does not like to be excessively revved while not in drive, because it over pressurizes.
Here is where i read that.. ZF 4HP22 transmission - Wikipedia, the free encyclopedia (near the bottom of page)

So, should I pull my front shaft and lock my t-case so they can put it on the dyno? or am i worried over nothing.


Also just wanted to say you guys are great on this forum. We have owned this vehicle for many years, but I have honestly never had to ask a question here until now because of all the info already here.

You guys have saved me a ton of time and money over the years.
Many thanks.

 

Is front drive shaft updated from oem, in that you have the extra grease fittings? If not, this may be a good time to do that as well. I have been active on this site for awhile, and I can't recall many posts about your concern. Not saying it is not an issue, just that it it were widespread you would think we would see a lot of it. What state are you in that does this level of testing?

 

Supposedly the problem was fixed in 1987. This issue is that when put in drive the A clutch was pressurized. When put back in park or neutral the pressure doesn't bleed off very quickly so excessive revving will burn up the clutch. Rebuilds suggest drilling a bleed hole in the clutch pack to help prevent the issue. I don't think the electronic transmissions are affected.

 

Have them put it in neutral when revving and there will be no issues at all.

 

I'll file that one under one of the dumber things I've ever heard.

 

Thanks all for the input, much appreciated. Sounds like it is not really an issue then.
As Savannah said also, would think it would be a much more widespread thing if it was really an issue.

In regards to the front drive shaft, we replaced that years ago after i read a few horror stories online here about it. Great advice to any D2 owner. When we re-built ours, the needle bearings were bone dry and wouldn't have lasted much longer.

And ZGPhoto,

this is copied and pasted directly from the government website for Ontario, Canada:

"Some vehicles, such as those with full-time all-wheel drive, cannot be tested on a dynamometer. These vehicles are given a two-speed idle test, where emissions of CO and HC are measured at "curb idle" and 2,500 revolutions per minute (RPM)."
All the testing facilities I've been to for emissions don't seem to be set up for doing a 4wd vehicle, and they insist on reving the engine in park.

 

In zf transmissions affected by this issue, this is not correct advice.

 

All right then, good to know.

 

Tell them to pound sand. If they're going to do emissions testing they should have a 4wd dyno. How do you think STis, EVOS, GTRs, Carrera 4s, and several other AWD vehicles get dyno numbers? I'll be going to a dyno day in the spring with my AWD S60R. There are 2wd, and 4wd dynos.

 

I fully realize there are 4wd dynos....i have seen one before.

I agree with you, they should have them for emissions here, but for some reason they don't.