Ok my jeep started this rattle after a run over a mountain pass this weekend.
It only happens when the jeep is warmed up and around range 1500-2000 rpm, in all gears. oil pressure is 40psi on start up then after warm 10 to 15 psi at idle, sometimes drops to 0 but never knocks, when im cruising it stays at 20 psi.
Specs on Jeep: 1990 4.2 118,000 miles with 4.0 head , HEI, motorcraft 2100 carb, AX-15, NP231 SYE.
Back in '08 I installed the 4.0 head and checked the compression and all cylinders where in 130-140 range, and rod bearing clearance all were within spec. In '10 I replaced the transmission with a recent rebuilt AX-15 with external slave and new clutch with resurfaced flywheel, at the same time installed the SYE in the np231.I run an el cheapo Mr Gasket fuel pressure regulator set at 4psi, for the 2100 carb. Recently in january '13 I replaced the timing chain and gears, along with oil pump and fuel pump. I did not replace the dampner at the time although the TDC notch was way off on the dampner I set motor to TDC and put a paint mark on dampner to give it a new TDC mark timed it at 8*TDC. it has ran great with no problems since then.
I cant quit pinpoint the location of the sound but it seems to be back of motor bell housing area. in the recording I have it in 4th gear and am just cruising at 45 mph, I let off the gas and the rattle comes in at 2000 rpm, then I accelerate and sound goes away, let off gas again and rattle again, then acelerate, goes away and... well you get the picture.
click on black spot to hear recording \/\/\/
At first I think its a detonation problem should I retard my spark?? am I running lean?? havent checked plugs yet, they are new bosch platinums, I know, I know
Or is it a pressure plate on the clutch chattering?? I cant tell Im confused
Rod bearings bad??