Misaligned Oil Pan - Cracked Trans Pump
Thread Starter
Teching In
Joined: Mar 2014
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Misaligned Oil Pan - Cracked Trans Pump Looking for some advice here. I've destroyed my second trans pump (4l65e) in less than 500 miles. First one lasted about 450 miles after I got my swap running. My trans guy suspected a runout or an alignment problem. Flexplate seemed to have a bit of runout, so I replaced that. The trans pump was replaced, and it appears to have failed after about 50 miles since I got it all back together.
After a lot of inspection, I have a suspicion that the oil pan is sitting proud of the back of the block by around .010". This was measured from the flexplate to the trans mounting surface (same location on the flexplate rotated around). I did have the pan off before I installed it, but I recall being careful to make sure it was a flush or slightly inset from the block surface. How can I check the alignment of the pan to confirm without any special tools? If it has been pulled back, do you think I'll need to pull the pan and fully reinstall with a gasket or will I be able to loosen it up and tap it forward? Could I have pulled the oil pan back by tightening the bell housing bolts into the oil pan before snugging down the bell housing bolts into the block?
After a lot of inspection, I have a suspicion that the oil pan is sitting proud of the back of the block by around .010". This was measured from the flexplate to the trans mounting surface (same location on the flexplate rotated around). I did have the pan off before I installed it, but I recall being careful to make sure it was a flush or slightly inset from the block surface. How can I check the alignment of the pan to confirm without any special tools? If it has been pulled back, do you think I'll need to pull the pan and fully reinstall with a gasket or will I be able to loosen it up and tap it forward? Could I have pulled the oil pan back by tightening the bell housing bolts into the oil pan before snugging down the bell housing bolts into the block?
TECH Resident
Joined: Mar 2012
Posts: 862
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From: Texas
Misaligned oil pan will not break a trans pump; if anything, you'll crack the oil pan.
You say that this is a swap; give us some details on the engine/ trans/ converter.
Also, the mods should probably move this to the auto trans board.
You say that this is a swap; give us some details on the engine/ trans/ converter.
Also, the mods should probably move this to the auto trans board.
Thread Starter
Teching In
Joined: Mar 2014
Posts: 25
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This is a swap in a 72 blazer. The engine is an LQ9. Trans is a built 4l65e mated to an NP205. Trans builder installed the output shaft for the NP205 and ran it on a dyno. Torque converter clearance looked good at about 1/8" of an inch. I just measured the new flexplate runout at a maximum of about .008", so that should be good. Flexplate to engine block measurements look consistent. Crank end play is well within spec from what I can measure. I've checked everything I can think of and the oil pan is the only thing off so far. The only thing I can't check is the torque converter runout. Not even sure how I'd do that without a special fixture or access to a big lathe.
Oil pan alignment is done with a 2’ straight edge placed along the back of the block at the bellhousing flange. Align the rear oil pan rail to this straight edge as you begin to snug oil pan bolts. Follow oil pan bolt tightening sequence and torque specs. After pan is torqued, you’ll not move it with the bellhousing bolts, as it’s a structural part of the engine at that point. I’m gonna move this over to auto trans section. You’ll get more traffic over there from folks that have seen this pump issue before.
Thread Starter
Teching In
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Some additional info. I mounted the torque converter to the flexplate to check the fit and runout. Fitment seems good at the crank pilot and mounting bolts. Runout at the torque converter drive shaft just behind the pump drive slots is about .005". Hard to get a reading because the flexplate sort of flops around and my dial indicator mount wasn't the strongest. Seems like Torque Converter runout isn't my problem.
I've ordered a better straight edge. I'll pull the flexplate and check the oil pan alignment a bit closer. It's the only thing so far that seems off.
I've ordered a better straight edge. I'll pull the flexplate and check the oil pan alignment a bit closer. It's the only thing so far that seems off.
Thread Starter
Teching In
Joined: Mar 2014
Posts: 25
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So, I suspect that my spacing must have been off at the converter. Plan is to replace the pump with a billet rotor and realign the oil pan. The question is, should the converter be replaced even if the snout looks ok? If the pump is cracked but the pieces are whole, and accounted for, would it contaminate the converter?
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TECH Junkie
Joined: May 2012
Posts: 3,051
Likes: 716
From: Poplarville, MS
If you can't find what is breaking the pump rotor, I would replace the converter just to try and eliminate another possible cause. If the rotor is as you say, "cracked but the pieces are whole", I would not replace because of contamination.
