Which rear main seal has the best track record on high mileage crankshaft?

Big Poppa Stew

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I'll Try to be short and to the point. Did research.. Read 500 posts on same topic.. "06 LJ / 4.0 / automatic... Just rebuilt engine/Rods,mains,RMS,rings,lifters,pushrods,rockers, all FelPro gaskets, honed cylinders, new oil pump, same crank and cam w/ 228K miles. time and money called for a budget build. Had the dreaded small drip at rear of pan. Did NOT use red anearobic sealant as suggest. 1st takedown I tried to add RTV under rear gasket on lip , major fail, it slipped out on install or something, oil poured out. Took pan down, removed rear cap, cleaned and dried EVERYTHING, Used correct sealant as per service manual. Red Anaerobic on bearing cap small bead on both sides where shown in manual. Ultra Black RTV in 4 corners sparingly (blue FelPro pan gasket). Hours and Hours of reading and youtube to make sure I was clearly understanding. Buttoned her back up (used recommended torque specs on all bolts 7 & 11 ftlbs) and still leaks. removed inspection plate to find drip (every 10 seconds approx.) coming off center of rear oil pan lip at idle and worse with throttle. Doesn't appear to be getting slung on flywheel like RMS leak (but I didn't drive it). Pan shows evidence of abuse (she's no street queen). Looks like the rear lip of pan has been massaged by someone, probably when I had trans rebuilt. So, 100% not rear of valve cover or sending unit or oil filter or any other common culprits. About to order the Spectra replacement oil pan and new RMS & gasket to take it apart for the 4th and hopefully last time. At rebuild I use the FelPro RMS, but noticed on amazon there is a DNJ brand and whatever the OEM sells at dealership.
Questions:
- Most seem to use Felpro , Is it the best or does anyone have opinion on other RMS brands? (im replacing while im in there to eliminate possibility that I damaged seal)
- I bought the loctite red anaerobic gasket sealant #51817 and waited about 30 hrs before I put oil in and started. Is that the right stuff?
- I've seen many use additional RTV , glues, Offsetting the 2 piece RMS, ETC... , I chose to stick to the books and failed. thoughts on other than spec methods?
- I need the technique with the george foreman guaranty not to leak (for a while anyway) so I can finish getting this thing to reliable daily status again. Trying to not have to buy a vehicle by investing some $$$ in my jeep.
 
From doing 2 piece Chevy RMS I clock the seal so the seam is at the 2-o-clock and 8-o-clock position, instead of 3 and 9. I’ll dab a little RTV at the ends of the RMS halves, not enough to make a booger, but just a light film. I never had a repeat leak …
 
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From doing 2 piece Chevy RMS I clock the seal so the seam is at the 2-o-clock and 8-o-clock position, instead of 3 and 9. I’ll dab a little RTV at the ends of the RMS halves, not enough to make a booger, but just a light film. I never had a repeat leak …

PS: I am about to do and RMS on my LJ. While I am there I’ll be doing my harmonic balancer because it’s looking crack-a-licious… because I am OCD, I’ll be doing the oil pump, timing chain and OPDA. Parts are cheap enough to slam on there while I’m in there.
 
Looks like the rear lip of pan has been massaged by someone, probably when I had trans rebuilt.

More experience people than I on the RMS but this comment caught my attention. When working with the tin covers- it’s well worth your time to make sure the flange surface is flat- bolt holes are not looking acorned from over tightening. You might want to order the pan- Sounds like you have had a little time with that pan so you are probably the best person to know if it can be worked straight or buy new.
 
FWIW, here’s my experience - I did mine 4 times as well. Felpro seal with mopar anaerobic sealer. I listened to Jerry and used high mileage conventional 10w-30. To be specific, the brand was STP because that’s what was available at the local autozone. It still had a small drip afterward, but it slowly got better and after a few weeks it was completely gone. Still dry now. Stuck to what the books said otherwise in terms of where to put rtv and positioning of the seal (not offset).
 
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Did mine four times too. Three FelPros. Mopar seal finally did the trick and red Loctite according to the picture that's floating around here.

Also did an oil pump and timing chain along the way.

Take the time to pull your bearing and see if you can read the numbers off the back...

And if the bearings are toast now's the time to roll in a new set...not terribly expensive and if it gets you more miles amen.

-Mac
 
I was all set to replace my rear main seal and decided to try this stuff - BlueDevil 00234 Rear Main Sealer. It took about a week and the leak stopped. It's been 4 months since I did that and still no leak. Might be worth trying before you replace the seal. Can't hurt.
 
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FWIW, both my LJ (78k miles) and YJ (175k) had oil seeping out between the engine and transmission, and I dreaded having RMS leaks. In both cases, the leak was completely fixed by replacing the oil pan gasket only.

If you suspect your oil pan is bent/damaged, I’d address that first.
 
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I was all set to replace my rear main seal and decided to try this stuff - BlueDevil 00234 Rear Main Sealer. It took about a week and the leak stopped. It's been 4 months since I did that and still no leak. Might be worth trying before you replace the seal. Can't hurt.
Such seal restorative chemicals can and do help though I prefer running a High Mileage conventional engine oil which has them already. If you tend to run synthetic engine oils, which are more prone to causing RMS leaks, you might try switching to a High Mileage conventional like a 10W-30 instead.
 
I have had better luck with the mopar rms than the fel pro rms.

I'm getting ready to do my RMS with a Mopar. I read on here that some of the Fel-Pro sometimes comes with a small plastic piece that helps you push the upper section into the groove without unintentially cutting it on the sharp edges, but mine didn't come with one. Is this an issue? Or can I just carefully and slowly push it in so if it catches an edge I can back it off a bit and gradually work it in.
 
Such seal restorative chemicals can and do help though I prefer running a High Mileage conventional engine oil which has them already. If you tend to run synthetic engine oils, which are more prone to causing RMS leaks, you might try switching to a High Mileage conventional like a 10W-30 instead.

agree. I started running high milage oil too.
 
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I'm getting ready to do my RMS with a Mopar. I read on here that some of the Fel-Pro sometimes comes with a small plastic piece that helps you push the upper section into the groove without unintentially cutting it on the sharp edges, but mine didn't come with one. Is this an issue? Or can I just carefully and slowly push it in so if it catches an edge I can back it off a bit and gradually work it in.

I had both at the time, and used the fel pro plastic shims and the mopar seal. I can’t speak to their effectiveness but I would do anything in my power to get it right and not have to redo it. I have also read about people cutting a plastic straw in half to use for the same purpose.
 
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I had both at the time, and used the fel pro plastic shims and the mopar seal. I can’t speak to their effectiveness but I would do anything in my power to get it right and not have to redo it. I have also read about people cutting a plastic straw in half to use for the same purpose.

Plastic straw it is. Thanks man!
 
My rear main seal only has 11,000 miles on it, it was dry as a bone when I brought her home with Rotella 15/40 in her. I changed to 5W-30 synthetic and she started leaking. I just switched to hi mileage 10W-40 synthetic blend as I heard that synthetic blend has barely any synthetic in it. After 200 miles the drip has almost stopped but still there, not sure if it will clear up with the synthetic blend. If not I'll try pure conventional.
 
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Thanks all, installed new spectra oil pan / felpro pan gasket/ mopar RMS. Used mopar anaerobic on bearing cap and ultra black rtv. Mopar anaerobic as specified by service manual on bearing cap and rtv only in corners as specified in service manual except for putting a dab on the ends of RMS. I did let it sit for 24 hrs before adding oil and starting. All seems to be good except for a leak at the pan plug. The spectra pan has a metal washer with no gasket. I was skeptical but tried it. Will be adding a rubber gasket to plug. Even though engine is freshly rebuilt I went with the penzoil high mileage 10W30. So far so good!
 
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My rear main seal only has 11,000 miles on it, it was dry as a bone when I brought her home with Rotella 15/40 in her. I changed to 5W-30 synthetic and she started leaking. I just switched to hi mileage 10W-40 synthetic blend as I heard that synthetic blend has barely any synthetic in it. After 200 miles the drip has almost stopped but still there, not sure if it will clear up with the synthetic blend. If not I'll try pure conventional.

add some BlueDevil 00234 Rear Main Sealer. It should stop. Then switch to hi milage conventional at your next oil change.