I can hear the collective gasp from here. ;-) However, for those of you who haven't recoiled from the shock of someone indicating this action, listen up, have I got a story for you!

I was doing some maintenance type things on my favorite toy and decided to change the differential oil. "Ah", says I, "let's really do a bang up job and use the good stuff!" Reaching into my cabinet I picked out a bottle of synthetic gear oil (from last years race season)and proceeded to pour it into my differential .... after carefully measuring out exactly 6.7 ounces.

Proud as a peacock because of all the fine work just completed, I proceeded to wipe the bike down and hopped on it for a quick ride. Within a few miles I noted a knocking noise coming from the front end. "Egad!" I said (well maybe it was something just a bit more colorful), "what in the blue blazes is this?". I checked the front end and could feel a knocking when the handlebars were being turned. At that point I was ready to yak (hurl, upchuck .... take your pick). I checked the boots .... nothing wrong there. I checked to ensure that the drain plug had not backed out. Nope ... it was fine.

I came to the conclusion that the problem was internal. After I came to and my vision had steadied I decided to email a couple of the folks that I met on this forum. One person thought that it may be a bad cv joint and gave me some suggestions as to how to check. While I was checking, his statement " ..... I think those babies are about $300 a piece" was bouncing around my noggin. Luckily the checking indicated that the c/v's were ok.

I then received an email from Gordon Banks. Gordon said "Look dimwit (actually he didn't call me dimwit ... but he should have) you are not supposed to use synthetic in the differentials. It makes the plates grab". He then proceeded to tell me how to fix it.

The "repairs" involved draining all of the oil and filling the differential with kerosene and driving around the yard for a few minutes. I actually did this three times before the kerosene came out clean. I then put the proper oil in with an ounce of GM differential additive (as per Gordon's suggestion). Now it is back to where it should be .... nice and smooth.

Moral of this rather long winded story?:
1) Make no assumptions when performing maintenance on your bike. Following the manufacturer's suggestions is the safest thing to do.
2) Always keep in mind that there is a wealth of knowledge available to you from these forums. Don't be afraid to use it.

Temp

 

I did close to the same thing, except I put it in the Tranny of my 90' Toyota 4x4 and withen 6 months the snycros were almost gone, I drained it out and filled it with normal 80W90 but the tranny still shifts very poorly as the 2nd to 3rd shift is very notichy along with the 4th to 5th shift as well. I have read at www.off-road.com that snythtic is to slick for limited slip diff's and manual trans and as your force a shift the snycros take all the abuse because the friction is not there to speed up the next gear set (same idea with a limited slip) and that is the grinding you here.

 

On the contrary, tempest, I think you've discovered a new product: "Locker In A Bottle!"

(No, that's not, "Liquor In A Bottle!")

Seriously, now, if you have a way to make those clutches in the limited-slip differential "stick," think of the money you've saved over buying and installing a locker!

Someone complains about one front wheel spinning? Sell 'em a bottle of this synthetic joy juice of yours!

Best wishes on this lucrative enterprise; I'm available as a consultant for a nominal percentage of the gross!

Tree Farmer

P.S. The symptoms you describe are identical for bad driveshaft bearings and/or U-joint; I hope not, but you may have problems beyond the lubricant choice.

T.F.

 

T.F. thanks for the business opportunity offer. Unfortunately the sound/vibration has completely disappeared.

We'll just have to wait until I screw something else up.

Temp

 

Thanks for the info. on this. I did the same thing. BUT, the Mobile 1 synthetic I used said it was compatbale with limited slip differentials. No that you mention it, I do sometimes hear my Suzuki front end make some odd noises. Should I drain it and use regular 80W90?? Hey, I tried to used the best!

 

WVTman my advice is better safe than sorry. Try this ... while sitting on a cement floor (with the motor off) aggessively turn your handlebars from side to side. You should just hear the rubber of your tires. If you hear anything mechanical I would switch back to regular gear oil.

Just my humble opinion.

Temp

ps If you do have the knocking noise then maybe you, T.F. and I can get into business selling that liquor er, locker in a bottle.

 

There has been some debate as to the type of gear lube to use in the front limited-slip differentials so maybe this will clerify things a little. I have personally used 75-90 synthetic and although it may lubricate as well or better then standard gear lubes in certain instances it causes alot of noise from the limited-slip clutches. I have recently changed to a good quality 80-90 gear lube and added the limited-slip diff additive. This works well, but the additive can be hard to find at times.
A friend of mine changed the oil in the front differential of his ATV, but instead of using the limited-slip additive he just used:

Quaker State
Hi-performance
Gear Lube,
Thermally Stable/Limited Slip
80w-90ep

Since then his front differential has been even quieter then from factory, no noise at all. I have since changed diff oil again and used this Quaker State product.

 

Correct me if I'm wrong, but it appears as though you are all saying the same thing.. let me sum up:

1. I put in synthetic gear oil, and the front end started chattering.

2. I drained the synthetic and put in regular 80/90 gear oil AND limited slip diff fluid.

3. The chattering stopped, therefore the synthetic oil was the cause of the problem.

Did any of you ever think that the chattering came from the lack of limited slip diff fluid, and NOT from the synthetic gear oil? I personally just installed an Auburn positrack in my Bronco, and the instructions stated that either normal 80/90 OR synthetic could be used, but you must also use the limited slip diff addative, or else the clutches in the differential would chatter. DING DING DING! *Light turns on above head*

I suppose I could be wrong, since I've never experienced this problem, so I've never had the chance to investigate it. Does the Honda service manual say specifically NOT to use synthetic oil? And does it say anything about the Posi addative? I don't think synthetic oil is as totally different from regular oil as some of you make it out to be.

 

Oh, by the way, I think regular 80/90 is plenty good enough for transmissions and differentials, where the clearances aren't nearly as tight as in engines, so they can stand quite a bit of wear. Synthetic is overkill, but extra peace of mind for some people.

 

I've found that the combination of synthetic oil and limited-slip additives does not work properly. The properties of synthetic oil are different from regular gear lube. There may be a brand of synthetic gear lube available that will work with the additives or a special additive for synthetic oils, but I haven't heard of any yet.
Up north here, we like to use synthetic oils where possible because it doesn't thicken in cold weather like conventional oils.