Right Rear gear lubricant, change to synthetic?

[The_Handier_Man1]

From: Jim83Itasca  (Original Message)
Sent: 10/17/2004 6:55 PM

Hi folk's
I have been thinking about changing the differential oil in my (83) P-30 Itasca since it now has 26,000 miles to a synthetic.
Also believe it has a open rear end so no special additives will be needed and i also prefer "Royal purple" but mobile syn is also agreeable so the question is what weight oil does everyone think it should be changed to.
TIA

Jim 



From: cooneytunes
Sent: 10/17/2004 8:16 PM

Depending on what climate you live in, if you live where temp. goes below freezing and with winter comming on, then I'd go with an 80/90 weight. I live in southern Indiana and this time of year it could be 30 at night and 80 during the day. So I just did mine and used 80/90....
If you live in very hot climate, south or s/w where temp seldom falls below 40 and in summer is consistantly 90 or above, then I'd go with straight 90 weight. The 80/90 is a good weight for all around.
Timmy



From: HeavyHaulTrucker
Sent: 10/18/2004 12:25 AM

Timmy is right on the money with the 80W/90 synthetic for year round use.  Some shops may recommend the 75W/140, but this is best for "severe duty" use like off-road tandem rear ends for big trucks.

When you switch over, make sure you have the rear end completely flushed with kerosene to get out all of the old petroleum-based oil out.  Contamination by petroleum-based oil is the number one failure cause with synthetics; it reduces the lubricating capability of the synthetic and increases the likelihood of scoring & scuffing.

You can easily do this yourself.  In order to do it properly, you will need to remove the rear cover after you drain out as much as you can through the plug -- this is to make sure that ALL of the old petroleum-based gear oil drains out.  Let it sit, open, overnight to drip; it is best to put the rear end up on stands so that you can do the flushing later.  In the morning, put the cover -- with the old gasket still in place -- back on; you don't need to really torque it on good, though.  Fill the differential with 2 quarts of K-1 kerosene, and put the plug back in finger tight.  Then start the engine, and put it in gear -- first Drive, then Reverse -- a few times; just to let the rear wheels spin at idle speed to flush out the wheel bearings and pinion.  With no load on the differential or bearings, you will do no damage like this.

After 5 or 10 minutes of this, shut down and let the wheels stop spinning.  Drain the kerosene and remove the rear cover; you will need a new seal anyway.  Use a rag to "mop up" the kerosene left in the bottom of the housing.  I suggest that you not use a gasket; use Permatex High Temperature Black or Permatex Aircraft Gasket Cement if you can find it -- do not use fiber gasket material, unless you want to have leaks.  Synthetic gear lube or synthetic motor oil, when it gets hot, will leak through any opening or porous gasket known to man!  Once you get the rear cover back on, fill the differential with synthetic until you can stick your little finger through the fill hole and feel the level.  Put your plug in finger tight, and run the rear end for a few minutes to get the synthetic oil up into the wheel bearing cups; then pull the plug and top off the oil level before you tighten the plug down.

If you did this right, you will probably never have to do it again for the rest of your life.  I did my 1994 Kenworth like this (only difference was I had to do 2 rear ends!) back in 1996; when I sold it in 2004, it still had the same synthetic and differentials that I started off with.  The new owner is still running it, and it has almost 2 million miles on it now!  It routinely pulls loads where the entire rig weighs over 150,000 lbs, and rear end temperature has never gone above 200 degrees even with that kind of weight, using synthetic; before the changeover, the rear ends used to run 215 to 230 degrees.  Your RV rear end should run no hotter than 165 degrees with synthetic.

John



From: Jim83Itasca
Sent: 10/18/2004 12:02 PM

John & everyone else thats the info I was looking for especially the gasket item, I live in the "Palm Springs area" with summertime temps that reach 115º plus and that synthetic gear oil will do the trick.
Again thanks everyone.

Jim



From: Jim83Itasca
Sent: 10/21/2004 9:43 PM

Well i have found (sold by the quart) "Valvoline 75-90" syn gear oil but nothing else sold by the quart.
Now "Royal purple" 80-90 & 90 weight is sold by the 5 gallon pail   so i have e-mailed them with my gripe.
Any other ideas cuz i really have a bad feeling about using 75-90.

Jim



From: HeavyHaulTrucker
Sent: 10/22/2004 2:17 AM

Jim, go to the Travelcenters of America (Coachella, Interstate 10 at Dillon Road) and go to the truck shop.  They will have synthetic oil in anything from quart to gallon quantities.  Also, if you bring your own jug, they will sell it to you by the quart too.

John



From: HeavyHaulTrucker
Sent: 10/22/2004 2:21 AM

BTW Jim, the 75W90 you found in quart bottles (squeeze bottle, right?) is probably wheel hub oil -- not the same thing that you need.  If you go over to the T/A, they will sell you exactly what you need -- take your own gallon jugs (2) and they will sell it from bulk cheaper than you can buy if off the shelf.  Make sure to tell them that you are using it in a rear end.

It is (from your place) the next exit past the big casino --- in fact, it is the last exit before you start to climb the big hill going eastbound on I-10.

John



From: Jim83Itasca
Sent: 10/22/2004 11:47 AM

John, I thank you very much for a great place & idea.
T/A is on my daily trip route to the salvage yard areas where the M.H. is stored  plus the mechanics and I have been friends for years.
I have the feeling that big rear end will consume 4-5 quarts and if anything is left over i can sell.
Again thank you for the splendid idea.

Jim 



From: Jim83Itasca
Sent: 10/22/2004 2:44 PM

Hi again John
Well i recieved the answer from "Royal purple" and the technical advisor Patrick Burris states "Yes you can use the 75w90 in place of the 80w90, you will never notice the difference".

Thanks
Patrick Burris
Technical advisor
Royal Purple Ltd.
1-888-382-6300 ext 241
Direct 281-577-5041
Cell 713-705-9201



From: HeavyHaulTrucker
Sent: 10/22/2004 11:46 PM

Hmmmm.... Jim, that is a totally different answer than I got from SpeedCo when I was doing this on my truck.  Of course, they are a Shell distributor so maybe their formulation is diffenent.  They told me that it is not the same, and to never use wheel hub oil in a rear end.  Maybe they were just trying to push something off on me (same product, different package?).

John



From: Jim83Itasca
Sent: 10/24/2004 12:08 PM

Hi John
Who knows anything/anymore!
I see the "Royal purple" is a max gear (GL5) but on the other hand so is "Mobile1" a GL5  differencial gear and sells for around $7.00 a quart.
On my (83 P30) his parts computer screen stated 7 quarts and since I dont know what size the ring & pinion is I'll hafta go with that estimination.
Hope the (GL5) can live up to it's tuff claims.

Jim