Transfer case drain interval
 

I like to do the whole remove the tranny pan and flush thing every 10k or so because I feel the 4L60E will last a long time. And doing tranny work is a pain in the butt so anything I can do to prolong its life is good. I also change the filter. While looking under the car I noticed the tranny goes straight into the transfer case which then goes to the rear axle. So I thought, when driving in daily use (2x4 mode) is the transfer case "being used". In other words, is the fluid in there being used ONLY in 4x4 mode, or, both 2x4 and 4x4 mode?

It's not much of a pain to do these flushes because I barely put any miles on the car (it takes me about 4 years to put 10k on the car). The reason I was wondering is because I was thinking maybe I should flush out the transfer case too when I do my tranny pan flushes. The transfer case doesn't even hold more than like 1.5 qts (if my memory is correct) so it's not like it cost much to do.

Also, I'm gonna change out the rear bearing seals (at the end of the axles) and didn't wanna buy the wrong part due to all these crazy axle sizes I see listed with the seals. rockauto.com has like 10 seals listed for my '01 ZR2 with axle sizes like 7.625, 8.625, etc. Shouldn't ALL '01 ZR2 rear seals be the same?

Thanks!

The t-case fluid is getting "used" no matter 4WD or 2WD, so it doesn't hurt to change it. If you do, you might want to actually remove the FILL bolt first, and see if any fluid comes out. The input seal between the t-case and the transmission is known to leak on these vehicles, causing the t-case to be over-full with fluid. When that happens, eventually it will ruin the vacuum switch on the top of the t-case. There's really only 2 ways to know if the input seal is bad (without taking off the t-case, anyway) - an over-filled t-case, or finding tranny fluid in your vacuum lines. The latter is a much less enjoyable.

Hmm, thats very good info. I have heard that the vacuum lines could get full of fluid but I didnt know it was because the t-case over filling due to a bad seal. the last time i emptied the t-case, the level was good.

any comments on the rear seals?

I figured out what the difference was with the seals. It has nothing to do with 7.6 or 8.6, etc. It has to do with whether the car has limited slip or not. only some 7.6 have that, but all 8.6 have it. i thought all ZR2's had limited slip.