Oddmodman Posted May 9, 2014 Share Posted May 9, 2014 Hi guys I'm looking at changing my RMS on a 4.0 that's out of its bay and is being used for a 2.5 to 4.0 swap. As far as I know the rms does not leak. but it has 180k miles on it, and the engine's already out, so as dad says, 'better safe than sorry'. That being said I figure I should replace the rms while the engine is divorced from its comanche since idk the condition of the rms. So I've checked Rockauto and they have lots of options. Should I go with one-piece, two piece, brand...? I figure one piece would seal the best. I just don't know if it would be better in the long run cuz I'm pretty sure the next time I'd have to change it it'll be in the truck and a one-piece unit would be harder to remove. FYI first time changing rms. Also, going with the cheapest one-piece oil-pan seal rockauto has. Link to comment Share on other sites More sharing options...
MuddFoot Posted May 10, 2014 Share Posted May 10, 2014 I'm pretty sure its a 2pc thats what ive used in 3 rebuilds. soak in oil before install Link to comment Share on other sites More sharing options...
Bornindesert Posted May 10, 2014 Share Posted May 10, 2014 What I do know is the 2.5 RMS is a one piece, the 4.0L is two piece. I'm a big fan of Felpro, don't like buying the cheapest or most expensive when on RockAuto. On the 4.0, be very detailed on the rear bearing cap, the groove and mating surface on the oil pan and the corners. It's tricky getting the one piece seated back there, so just pay attention. don't over tighten the pan bolts, use a torque wrench and then re-torque after the sealant has cured. A small dab of silicon sealant on each bolt is not a bad idea, just extra work. Using a product like Hi-Tack, spray on gasket sealer keeps things in place during assembly. Good luck!! Link to comment Share on other sites More sharing options...
Oddmodman Posted May 10, 2014 Author Share Posted May 10, 2014 So given the option, should I go with a two piece or one piece? And wouldn't grease be better than oil? Link to comment Share on other sites More sharing options...
Eagle Posted May 10, 2014 Share Posted May 10, 2014 So given the option, should I go with a two piece or one piece? And wouldn't grease be better than oil? You don't have an option. The 2.5L uses a one-piece rear main seal. The 4.0L uses a two-piece rear main seal. Oil it. Link to comment Share on other sites More sharing options...
Oddmodman Posted May 11, 2014 Author Share Posted May 11, 2014 >>> What's this? http://www.rockauto.com/catalog/moreinfo.php?pk=1118220&cc=1181720 Link to comment Share on other sites More sharing options...
Oddmodman Posted May 11, 2014 Author Share Posted May 11, 2014 Says it's a rear crankshaft seal aka rms. Link to comment Share on other sites More sharing options...
Eagle Posted May 11, 2014 Share Posted May 11, 2014 >>> What's this? http://www.rockauto.com/catalog/moreinfo.php?pk=1118220&cc=1181720 They list it as a rear main seal but I think it's actually the front crank seal. The rear seal for the 4.0L is a two-piece seal. But go ahead and buy the one you found, and be sure to let us know how it works out for you. Link to comment Share on other sites More sharing options...
Oddmodman Posted May 11, 2014 Author Share Posted May 11, 2014 No that clears everything up. I kept looking at rockauto and there were clearly two options, a 1pc and a 2pc, and everyone kept telling me there is no 1pc. So, your explanation makes more sense. Thanks. Link to comment Share on other sites More sharing options...
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