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96 XJ AW4 buzzing

markaboo929

NAXJA Forum User
Location
Mooresville,NC
Hello I have a 1996 XJ with an AW4 4 x 4 transmission. I get a buzzing sound underneath from the torque converter / pump area when it is cold. Intermittently the transmission seems that as it warms up that it's not shifting as crisp as it does when it's cold mostly when it kicks into overdrive it seems like it's slipping a tiny bit. I almost have a feeling it's the pump but not exactly to be sure I have not heard a buzzing sound out of this out of any automatics that I have encountered GM Transmissions anyways. Here is a video of the sound to see if anybody has experienced if a pump or torque converter is the issue.
https://youtu.be/dB0Lq3dbEOg
 
I wish someone knew what this was because mine has been doing this for months. Yesterday twice after I came off the highway it acted like it was slipping and having trouble shifting but went away after I shut it down for a few minutes. On my way home it actually started squeaking like the belt but from under the jeep. I haven't serviced it in the 85k since I put it in so I'm going to service it when I get back from vacation monday, but it already had supposedly 100k on it when I put it in so it may just be done. Postal miles are hard on parts.
 
I believe it is the pump. If ya think about it the sound is similar to a ps pump low on fluid.
I have a feeling that when it happens the clearance between the gears get excessive and cavitate fluid and lose pressure. The correct way would be to drive it with a pressure gauge attached. And what would explain is when you shut it off the gears relax and sort of reset their position and then everything is fine again. I have experience rebuilding GM automatic and never had this issue with any pumps on those.
I am going to receive a another transmission and rebuild that one. I do have a two-wheel drive transmission that was working fine when I upgraded to two-wheel drive to four-wheel drive. I just might swap out the pump on mine currently in use and see if that cures it and if it does this will confirm auspicious
 
I wouldn't change out the pump unless you are really desperate as the are so many bearings/bushings that exist right at that connection point of the torque converter!
 
Update on mine: back from vacation, bought a filter, some valvoline max life and dropped the pan. After 85k postal miles there was hardly anything on the magnets and only a fine, thin film on the pan; but the filter screen looked completely clogged with the fine particles! Cleaned up and put it back together with the new filter, shifts just fine and no pump whine. The real test will be the next time I work, but tomorrow I'm putting in a new set of rod bearings.
 
I did some internet searching on the A340 x Series E H F and so forth. I stumbled upon a Lexus Forum which has the A340 and there was a video posting the exact same noise mine was doing. What I ended up doing was dropping the pan and looking at the screen and sure enough it was kind of like a blackish type substance. The pan had the same type of a film on it too. I had the pan off about 8 months maybe ago ti replace the solenoids and used Valvoline de/merc II,III fluid.So I replaced the screen filter and this time as from the Lexus Forum I decided to use the Toyota T-IV fluid.I know what ya all are thinking dex III only.However the lexus forum all swore by that fluid.After all the AW4 is a Toyota Aisin unit.The pump was starving for fluid causing the noise and not enough volume/pressure to keep the clutch packs together. The trans shifrs like new I am very happy with the outcome!
Next time your AW4 buzzes I would change the screen first before thinking the pump is bad.
 
Update on mine. It still dosent make any noise but the slow going into 2nd when cold is back and slightly worse. It still works great until I let it set for 10 minutes then it acts up for a mile again. Not enough of an issue yet to warrant me tearing into it. A tranny guy I asked said it probably wasn't electrical, either a spool valve hanging up or valve in the body is hanging up.
 
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