Synthetic Gear Lube Weight - Ford F350?

I have a 2000 24' Coachman motorhome on Ford F350 chassis. Once and a while I'll tow a small/light trailer.

I want to switch to a synthetic rear axle gear lube to help with the gas mileage but don't know what weight to use.

I want to use the lightest weight I can get away with considering I rarely drive over 60 mph and the total weight including the trailer will never exceed 14,000 lbs (but I do go up mountain grades).

Anyone have any experience with synthetic gear lube and suggestions for the weight?

Thanks,

Dennis

Reply to
Dennis
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Reply to
Jeff Strickland

Thank you, just what I needed to see.

Ford recommends 75w - 140w for synthetic.

Reply to
Dennis

Something about that manual doesn't seem right. I always thought that F-350's with dual rear wheels (I'm assuming you have DRW) used a Dana 80 rear axle and used 80W-90 gear oil. I'd be concerned that a 140 weight would be too heavy for it.

Now it's entirely possible that I'm wrong and back in 2000 they used the Sterling 10.5 on dual rear wheel trucks also, but I know that at some point they used the Dana 80.

The way to know for sure would be to look at the axle tag itself. If you can post the numbers from the axle tag, we can probably figure out what it is. Also, if there is a certification sticker on the drivers side door post (B pillar), it should list an axle code that is easy to look up.

Reply to
David Chamberlain

Ford at one time did recommend 75w90 or 80w90. They have since changed that recommendation to 75w140. My guess due to problems with the rears with the lighter weight. Use the 75w140. Alos if thge rear is a limited slip, make sure to get at least 1 bottle of the Ford friction modifier. Otherwise you will tear up the clutches.

Reply to
marlin.singer

If you would read the Owner's Manual for your Ford chassis you would find that it already has synthetic blend good for the life of the chassis. If you want to spend money on snake oil, have at it!!

Tom J

Reply to
Tom J

No lubricant is "good for the life of the chassis" if you plan on maintaining a long term relationship with your vehicle!

nate

Reply to
Nate Nagel

There have been hundreds of thousand vehicles hit the scrape yard with the original oil in the rear end. Some parts get contaminated by too much opening up the part and letting dirt etc in. Many people are still changing engine oil at 3,000 miles when most service manuals specify 5,000 to 7,000 mile intervals.

I have never changed the oil in a rear end and have never had a failure - some with over 250,000 miles. My truck and motorhome with Ford engines get engine oil changes every 7,000 miles and the transmissions get changed every

100,000 miles UNLESS the oil gets scorched.

Tom J

Reply to
Tom J

I agree about the engine oil changes. Following the manufactures severe service schedule will be more than is necessary for good engine life. Oil change places recommend every 3000 miles because they get to sell more service that way. I do mine every 5000 because that is the severe service schedule for a 6.0L PSD and I definitely fit the severe service criteria. If all your miles are easy ones, I would even go to the regular service schedule, but if you meet any of the severe service criteria I think it's a good idea to use that schedule.

100k on the transmission is risky, depending on the transmission. Again on a Ford F-250 (the only real example I have at the moment) the regular schedule is 30k. I would follow that. If the regular schedule is 100k that is fine.

As far as Ford rear ends, especially with a limited slip differential, I think you are taking a chance. I've seen plenty of LS 10.5's go 100's of thousands of miles without a hitch. But I've also rebuilt a Explorer LS rear end at less that 100k when the bearings failed, even though it was supposed to be a "lifetime fill." I think there is something about those LS clutches that can get you.

And I'm still somewhat concerned about the OP's motor home, because I was pretty sure that all F-350 DRW's after 99 used a Dana 80, and a Dana

80 requires 80W-90 and DOES have a maintenance schedule.
Reply to
David Chamberlain

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