OK, so 1991 4.0 TF999 with a few noise problems. Tell me what you think.
I was having a horrible noise at high RPMS...mostly at the 55 MPH+ range. My TF99 input seal was leaking, and I assumed the 12k mile tranny was wearing out and blamed the noise on the converter or pump. Well, I just swapped out the trans for a good one with a new converter and the noise is still there. It's only at high RPMs is noticeable when the throttle is applied, but more present when I just left off the gas and it coast back down to a lower RPM. It's more than the normal sewing machine noise. I loose no oil (other than needing a new valve cover gasket and oil pan gasket) and it doesn't burn any. I run 15W40 diesel oil right now. It was a rig that was sitting for a few years, so the motor has been through several oil changes in the last 500 miles.
Everything thing else is new and rebuilt, 1 tons, xfer case, driveshafts etc...so now after the tranny swap I am positive it's motor related.
It does do it when it 1st starts up from time to time, but stops after a second or so. SO is there any I should know to avoid a rebuild? Does it sound valve train related? I figured bottom end would be so bad it would have been catastrophic???
Cam, oil pump, rebuild head?????