No power below 2000RPM 5.7 xk

[07JeepXK]

You need to swap the fluid regardless on transfer case if it has 60,000 miles on it and never been changed. Try what Matt said with transfer case locked

[thance]

I'll check 4lo when I get home from work. Took the wife's libby today so mine wouldn't get any worse. I never had any issues in the Bronco with tcase or diff fluid and that was up to 170,000 mi. But, no limited slip or clutch packs in either, so it was quite different. (don't have clutch packs in the xk diffs as it is QT2, but the t-case likely does).

If it does work in 4lo after I drive it long enough to exhibit the problem could a fluid change fix it or are the clutch packs shot?

[Matt]

Dont drive it around too long in 4-low. Drive around in normal 4-hi until the issue starts, then shift into 4-low and see if anything changes.

If it does work in 4-low, you may just need the clutch packs rebuilt.

[thance]

Dont drive it around too long in 4-low. Drive around in normal 4-hi until the issue starts, then shift into 4-low and see if anything changes.

That's my intent.

Thanks!

[thance]

Test drove yesterday evening and to and from work today (35mi each way) and can't reproduce the issue......

[Matt]

I'd drop the trans pan and replace the filters for good measure. Could have a faulty/damaged filters thats intermittently restricting pressure. And at 65k+ miles, consider it good preventative maintenance regardless.

[thance]

I think its time to replace all my driveline fluids.

Friday was really hot, so that may of played into it.

Also I had an electronic pressure booster on the trans that I removed Sunday. That had been on for months, but maybe the hot weather helped it trigger something. Not sure....

Also removed the diablo tune for good measure.