454 Rear Main ???


Old 04-13-04, 10:29 AM
M W is offline
Thread Starter
Join Date: Oct 2000
Location: san diego, ca, us
Posts: 137
454 Rear Main ???

I have an 87 RV with Chev 454 in it. Looks like rear main is leaking. Seems to leak the worst when under load/going uphill for longer stretches....oil leaks out and down the exhaust system scaring the elle out of the wife and kids as it smokes up a storm. The worst time it did this I added two quarts. The next trip it barely did it and I added nothing. But my mechanic who does basic engine work says more than likely rear main.

While looking (in vain so far) for someone to do the work, I have found myself confused. I have been told the 87 was a two piece...one shop saying they could not do the work then becuase two piece are harder, then another telling me two piece is easier since you don't have to drop the tranny. Ok, which is it and why is it so hard to find someone to do the work? I have also been told it's a 3.3 hour job (by the book?) then I got a guy telling me its 18-20 hours.

Lastly, the 18-20 hour guy did tell me he would run a "thrust" test of some kind to determine if the work would be worth doing. He said this one hour test would tell us if the rear main job would even make a difference. Make sense?

Any advice or help would be greatly appreciated.....oh crud,one more small thing....

Just replaced carrier bearing to eliminate howl under the galley. That noise is now gone but a very similar noise further back near the diff. Ideas?

Thanks guys, always get great help here...
Sponsored Links
Old 04-13-04, 11:24 AM
carguyinva's Avatar
Join Date: Nov 2003
Location: Shenandoah Valley
Posts: 1,147
let's see here...

...first things first...testing crankshaft endplay (thrust test)...the etch will put a dial indicator on the end of the crank and measure how much axial movement there is of the crank. more than about .010 means you have another problem and removing the oil pan would be necessary to evaluate the extent of that problem. a good thing to do before just arbitrarily replacing the rear main seal.

as for whether it has a two piece or one piece...call the dealer and see what they list as the replacement... somewhere in the 80's is when they change from a two to one piece. replacing the one piece requires removal of the trans and is preferable to the other style...much easier to service. the two piece design requires removal of the oil pan and the rear main bearing cap...one piece of the seal is in the cap...the other half is in the block and wraps around the crank itself. this is obviously the difficult part...getting the new half around the crank...they are a real PIA...but doable. everyone prefers the one piece design, of course. hence the reason that some shops aren't interested in doing it unless it IS a one piece. as for the cost...personally, i wouldn't do either one on an RV for that amount (3.3 hours). pulling trannys on your back is NO fun and deserves to be well compensated. the 18-20 hour estimate is an outside guess...worst case scenario i guess you might say. he's figuring that if they can do it for less, so be it...but he's covered if things go slowly because it's a two piece...that way he doesn't have to tell you it was more than was originally anticipated.

now...having said all that...my advice would be to have that thing checked with dye and a black light to be absolutely sure of the location of the leak...your description doesn't ring all the way true to me. normally, a bad rear main pours oil as soon as the engine starts up and has nothing to do with load. leaking under load like that tells me you may have a problem with the crankcase vent system...your crankcase is building up too much pressure and forcing oil out somewhere...bad PCV valve, stopped up passages, bad filter...something like that.

lastly...get that damn thing checked out and repaired before you have a fire...RV's build alot of heat and that leaking oil will catch on fire with you AND your family in it while driving.

oh crud...*lol*...on your noisey bearings...while someone drives it...lay on the floor and pinpoint the location...if it's over the differential, it's probably carrier bearings...if it's load sensitive, probably pinion bearings. not real unusual on RV's as they are pushed to the limit of the chassis...and that's before adding fresh water, camping gear, etc, etc....anyways...i hope this helps you sort thru that dilemma and good luck finding someone to do the work
Old 04-13-04, 02:57 PM
M W is offline
Thread Starter
Join Date: Oct 2000
Location: san diego, ca, us
Posts: 137
thanks carguy

What exactly is the dye and black light test? I'm having a hard time finding someone to do the work....is this test something my engine mechanic can do? Or do I take it to the RV joint that quoted 18 hours and let them do the dye deal then the thrust test? It definitely does not "pour" oil when running, so maybe there is good news here.

Next, we already replaced the carrier bearing....and the noise went away further up. It made a huge difference. But there is now a similar noise further back right over the differential. When you push the gas, it makes the noise (in drive of course). When you let off the gas or shift into neutral, noise goes away.

BTW, if it takes 18 hours I have no problem paying the guy, I just thought there was a huge difference between 3.3 and 18.
Thanks for your help....I truly appreciate the guidance....I want to get this thing right asap so it doesn't lead to more problems.
Old 04-13-04, 06:41 PM
Desi501's Avatar
Join Date: Oct 2003
Location: Boynton Beach Florida
Posts: 2,207
The 3.3 hours is probably the reason your can't find anybody to do it. Working on a motor home is the worst vehicle you could get, especially if your shop isn't equipped to do this on a regular basis. Most shops just refuse to work on motor homes for any price. The RV shop is in that business simply because he demands enough money to make that type of work worthwhile along with buying the equipment that makes him capable of doing it. He may be a little on the high side but that's the reason he's willing to work on that vehicle. The dye and black light test consists of putting an ultraviolet dye in the oil and running it for a while. Now when you inspect it with a black light the oil will leave a definate trail of dye back to it's source. It will still be difficult because you don't have access to actually see the seal to be sure.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Display Modes