AW4 Prob - no pressure?!?!

Here's the low-down...

87 AW4/NP231 combo behind 4.0L swapped into Jeep Wrangler. Everything was kosher until 6mths ago when the rear driveshaft blew a u-joint at 70mph! Twisted the rear driveshaft, shattered the NP231 cone (was slip yoke style). Swapped in used cone and rebuild a driveshaft to work. Test drove showed major vibration, second look underneath revealed carnage to the trans/tcase adapter (tcase was attached by 1 of 6 bolts!!). At this point the YJ was still limpable, we were only up the street from the house - so we backed it into the garage to future work.

This past weekend, swapped in a NP231 w/ SYE and had custom driveshaft made. Also swapped in used adapter between the trans/tcase. Trans has 130k+ miles on it so we drained fluid and replenished with new Dextron III. Started YJ and nothing. Checked for leaks, nothing, ran for few minutes (build up temp), check fluid on dip stick - ice cold & no change! Spent hrs going through service manual, checking shift linkage, throttle cable adjustment, did manual test (remove TCU fuse), still nothing. Drained fluid, removed pan to check park rod/pawl - without removing valve body it appears to be functioning (I cannot move the output shaft when it is in park and can move it when it is in other gears). Reinstalled pan with new gasket - another refill of fresh fluid - still nothing. Performed pressure test - notta! Removed inspection plate and checked torque converter - it is attached to the flex plate - no probs there. Any idea's on what could have happened?

I'm wondering if its possible the oil pump has broken - I don't hear/feel anything grinding, nor were there any metal shavings inside the pan (at the magnets).

-Chris

sounds like a ft pump/convertor job. or a verystopped up screen in the filter(though unlikely)i'd get it o-hauled.

a-mechanic said:

sounds like a ft pump/convertor job. or a verystopped up screen in the filter(though unlikely)i'd get it o-hauled.

Click to expand...

Maybe you can explain to me how the convertor operates in an AW4 and how it would effect the hydralic pressure? I thought that the two knotches on the convertor lock into the pump - and if that's the case it should still be generating internal pressure as I verified it was attached to the flexplate per spec.

normally when i'm into a transmission with a pump problem especially anything with more than a few miles on it i replace the convertor also. due to the fact the three times i did not do so (for friends and myself)i had to go back in and replace all the seals as well as clean the valve body and the entire trans due to contamination from a convertor that dumped trash. and a lot of times the new pump to convertor seal area will start leaking because of thegroove the old seal wears into the conv. its just sop.

TTT - Still looking for advice and a response to my TC operation questions

Chris

The torque converter is a hydraulic device that couples the engine crankshaft to the transmission. The torque converter consists of an outer shell with an internal turbine, a stator, an overrunning clutch, an impeller and an electronically applied converter clutch. Torque multiplication is created when the stator directs the hydraulic flow from the turbine to rotate the impeller in the direction the engine crankshaft is turning. The impeller transfers power to the planetary gear sets in the transmission. The transfer of power into the impeller assists torque multiplication. At low vehicle speed, the overrunning clutch rotates the stator at engine speed (during torque multiplication) and allows the stator to free wheel at high vehicle speed on deceleration. The converter clutch provides reduced engine speed and greater fuel economy when engaged. Clutch engagement also provides reduced transmission fluid temperatures. The converter clutch engages in third gear. The torque converter hub drives the transmission oil (fluid) pump.
Hope this helps.

It does, a great deal. Thanks for the detailed response. Knowing the converter is directly coupled to the flex plate and the trans oil pump, the issue I have with no pressure being generated is most likely due to a bad or damaged pump. Only thing left to do is remove it and tear it open to find out what's really going on.

Any other ideas? Do you agree with my approach?

Chris