I'm running a 4r75w with a Circle D triple disc converter behind my 4.6. I first installed the setup around 2 years ago, and it ran excellent for 8000 miles or so.
I never had an issue with the stock shortblock, so I yanked it and swapped to a MMR rotating assembly in a new block. After 200 miles, my thrust bearing did this:
Crank end play on that engine was .007, and converter pullback was 3/16th. The machinist who did the work on that shortblock was less than professional, so I figured there was a metal shard that he and I had missed had gotten in around the bearing and chewed it to pieces. Bummer, better start again.
So this time, I put together another bottom end. Reused my stock crank, and block, got the converter inspected by Circle D, etc. Crankshaft endplay was .0065", converter pullback was 1/8th" (I quadruple checked), I used one of the best machinists in my area and I cleaned every oil port religiously after the work was done.
The result? Thrust bearing failed even more catastrophically than last time, this time in 150 miles.
I'm confident that my shortblock was assembled correctly since I did the work myself. I'm also confident that my converter was healthy (it was freshly rebuilt), and the pullback was in spec. With that said, the obvious culprit was my transmission killing these thrust bearings. The best theory I have heard thus far is that my transmission cooler was clogged or restricting flow, causing converter charge pressure to rise and wiping out my thrust. This is possible since I am still using some hard lines in the trans that could have been beaten up or pinched during the engine install.
I'm going to grab some new pistons and a crank to fix the shortblock, and when I put it back together I'm going to throw a pressure gauge inline to check my charge pressure on initial start. If I can confirm it's high, I'll swap the whole trans cooler setup out for something huge with AN lines.
I'm wanting your all's input on any other theories on what is going on. I'd be sick if I built this thing for the 3rd time only to have it die within 200 miles. I still have the dead shortblock in my garage so I can do all the forensic work required.
I never had an issue with the stock shortblock, so I yanked it and swapped to a MMR rotating assembly in a new block. After 200 miles, my thrust bearing did this:
Crank end play on that engine was .007, and converter pullback was 3/16th. The machinist who did the work on that shortblock was less than professional, so I figured there was a metal shard that he and I had missed had gotten in around the bearing and chewed it to pieces. Bummer, better start again.
So this time, I put together another bottom end. Reused my stock crank, and block, got the converter inspected by Circle D, etc. Crankshaft endplay was .0065", converter pullback was 1/8th" (I quadruple checked), I used one of the best machinists in my area and I cleaned every oil port religiously after the work was done.
The result? Thrust bearing failed even more catastrophically than last time, this time in 150 miles.
I'm confident that my shortblock was assembled correctly since I did the work myself. I'm also confident that my converter was healthy (it was freshly rebuilt), and the pullback was in spec. With that said, the obvious culprit was my transmission killing these thrust bearings. The best theory I have heard thus far is that my transmission cooler was clogged or restricting flow, causing converter charge pressure to rise and wiping out my thrust. This is possible since I am still using some hard lines in the trans that could have been beaten up or pinched during the engine install.
I'm going to grab some new pistons and a crank to fix the shortblock, and when I put it back together I'm going to throw a pressure gauge inline to check my charge pressure on initial start. If I can confirm it's high, I'll swap the whole trans cooler setup out for something huge with AN lines.
I'm wanting your all's input on any other theories on what is going on. I'd be sick if I built this thing for the 3rd time only to have it die within 200 miles. I still have the dead shortblock in my garage so I can do all the forensic work required.