Brought my '84 D100 home from my parents' house and had a bad howl from the rear end when accelerating or maintaining throttle over about 30 mph. This was the first time I had it on the road since buying it last summer. Only thing I changed to the rear end was installing a limited slip.

Did some research and went to check things out. The ring and pinion both looked quite rough on the drive side. The surfaces showed scoring, and you can feel them. They're not very deep, but they don't look good. There are no chunks or chips out of the ring or pinion.





Is this enough to cause the howl? I've read in several places that a worn gear set, specifically from overloading, can cause a howl over a certain speed range. No noise prior to adding the LSD, but the truck had been very abused by a number of its prior owners. I would imagine putting the strain of a LSD onto a tired ring, especially since it's probably not mating exactly as it had before, couldn't be helping. I would just like some advice before committing to a ring and pinion swap.

That case and those gears look remarkably clean and oil free. You had some form of oil in your rear axle, right?

If you can adjust that gear to get a good tooth pattern, you might be able to run them more, but setting up an 8 1/4 rear axle is a PITA. I would rather swap the whole axle than try and swap gears and adjust them.

I'd clean that out really well with lacquer thinner, fill it with 90/140, toss in a bottle of posi additive and drive it until it breaks.

I have to agree with Reed, it sure looks dry in there.

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Official Cookie and Mater Tormentor.

It had been draining all day before I took the photo. In the past four months it's been drained and refilled with fresh oil three times; I'd hope it would look clean

The gear and pinion don't look terrible, but the howl is quite loud. I'll get some marking compound and see if I can simply readjust it to get the wear pattern to sit together better.

I really appreciate the help!

Reed's PITA comment is an understatement. I PAID Steve, a pro, to set up my 8.25, and it still howled at 30 and 60mph. This was all new bearings and rebuild kit. I took it back to the guy who said, "Oh that's not too bad". I Sold that rear for cheap to a local who wanted LBP wheels for his 70 Valiant and put a Ford rear in mine.

Before getting rid of it I called around looking for someone who specialized in Mopar rears, and NO ONE wanted to touch the 8.25. I basically threw away $800 on that little project. I sold it for $150, and had to tell the guy it was noisy.

I still use Steve for other things. I trust and like him. But not for Mopar rears.

Sam

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Well, that makes me feel good about my new plan- dump it and use the 9.25" out of my brother's '85 W150.

I just picked up another long bed D150 just for the engine, transmission, and at the time- the rear end. However, upon getting it home I found it's the large bolt patter 8.25". So I'm just going to trade the whole roller to my brother for his rebuild on his first truck for the rear end out of that same truck. He can use the limited slip I put in my 8.25", but I'll have to get a new set up for the 9.25". I hate running an open differential in 2wd trucks around here.

Yes, that was my first thought, "hey did you have any gear oil in there..." OK, beating a dead horse.

BTW, when I replaced my ring and pinion my pinion seal was leaking and I had a very slight whine at certain RPMs. I drained the oil and replaced with Royal Purple. My gears were quieter and the leak was gone. However, this is not a commercial for Royal Purple. I recently read a report where RP scored pretty low, especially on oxidation and loss of viscosity over time tests. See: http://www.lastgreatroadtrip.com/wp-con ... arison.pdf

According to the above report, AMSOIL severe Gear was the best choice.
That said, it was AMSOIL research! Is it biased, who's to say? They certainly seemed to target one of their likely biggest competitors...

Does anybody know if RP is crap like AMSOIL says it is? My leak is still gone, but I have noticed a bit of the whine come back over the past year.

FYI,

Brian

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I replaced the "lifetime fluid" in my M5s transmission with Royal Purple gear oil and it made a huge difference. Shifts were much crisper and easier to engage than they had been previously. I can't say much on the longevity because I sold it after a few thousand miles.

I also used it when adding oil between changes. Never has any bad experiences with Royal Purple. Not a whole lot of choice when you have to use 10w60 though.

I picked up some heavier weight fluid, but haven't put it in yet. I have to replace the springs anyway (one's broken) and figured I'd just take the whole assembly out and swap it in one go. If I can't get the truck to my parent's without that god awful howl though, that's worth it to me