Hello All,

I've been fixing up a 1990 240 with 250K. I did a tranny flush with Mobil 1 last week about 300 miles ago. It has been shifting much better every day I drive it to work. 1-2 shift still has the bad check valve clunk, but you can hardly feel the other shifts. However, a couple of days ago it started making a horrible chattering noise in reverse. At first I thought it was the front brake pads I had just installed grabbing. But then I noticed if I put my foot on the brake and give it a little gas in reverse it makes the slipping, grabbing noise. I noticed the fluid level was a little overfilled, so I pumped some out and it did not seem to make any immediate difference.
It has not slipped when the car is cold. All forward gears work perfectly. The shift linkage is adjusted properly. I was hoping to just replace the 1-2 check valve ball and get some more miles out of it. Anyone know what might be the culprit, valve body, clutches, etc..

Thanks,
Preston

I second Steve's opinion. If it sucks at shifting and slips, so long.

First, make SURE that it is slipping and chattering, not something else like bad U-joints, mounts, or something else. You probably have identified it already as the trans, but just in case, DOUBLE check it.

The 1-2 clunky shift is not a reason to replace an AW70, and it usually does not get solved by new fluid. If anyhting it gets worse in my experience. But it doesn't kill the transmission either, I have plenty of first and second hand experience with these problems.

I solved my shuddering in reverse "transmission" problem today. As it turns out is wasn't even the transmission at all. I had decided to replace the filter screen in the transmission thinking this might help the reverse noise. While I was under there I also replaced the transmission mount. When I started the car up, the same shuddering noise I heard in reverse before was now occurring in all gears, even in park. Now I knew that it must not be a transmission problem.
Looking and listening around with the engine running, I found that the exhaust header was banging against the transmission crossmenber. When I replaced the mount, it raised the level of the transmission to where the header was banging all the time. Before, the header was far enough away to only contact the crossmenber when the engine/tranmission torqued the other way in reverse. As to why it didn't make noise when the car was cold, I think driving loosened up the mounts and caused to exhaust to move closer to the crossmember. The actual problem was a bent exhaust header. The back end was bent upward and there was only about a 1/4" clearance between it and the crossmember. I looked at my other 240 and there was enough room between the header and crossmember to easily grab your hand around it. I took the header off and stuck it in the fork of a tree and bent it back straight. Upon re-installation, the awful shuddering noise was gone.

On a side note, when I had the pan off the tranny, I couldn't believe how clean it was, I figured there would be some metal on the magnet but there was only a little fine black paste, which I'm assuming came from the clutch steels. It has 250K on it and the PO never changed the fluid. This is one tough transmission.

Preston
1990 240 110K, Daily Driver
1990 240 250K, Wifemobile

Even a check valve is some work to replace, made less desirable by the presence of numerous good used trannies out there for $300 or so. If you conclude this is gone, forget about tearing it apart and just replace it.