Outdoorsman, if you go and read carefully “installing aftermarket differential” discussion, you can see that I am saying we have limited slip differentials G86. There are a lot of us would like to replace limited slips with lockers. I have post QS trucks rear axle diagram together with the limited slip differential diagram in that discussion. I have also posted a sample locking differential G80 for the comparison purposes.

I believe posts under this discussion will definitely help someone who wants to understand how the two differential work.

Hope this will clear your questions. I never claimed that I am an expert. I only share the information I know and experienced, and would like to see the same from the other members. There never been an issue on this and similar forums who is right or wrong, we just share and learn each others experiences and have fun when doing that.

Just take it easy…

Sounds great! Guess following the post accuratly is a bit difficult sometimes. Guess one of us is not reading right as both diagrams you posted say LOCKING. This is my point! Neither diagram fits what Ive seen and read as to the way the unit is built and whats in the QS. If you are positive and have seen the one according to the diagram you say is the one of the LSD in the QS then I stand corected! If on the other hand its a diagram that cant be confirmed then it fits what I said about puttting information out there that we dont know as fact. Ill know first hand as soon as mine comes in for replacement. I personally am not going to throw something out there to confuse the others if I dont know it first hand and seen it or experienced it myself with my own eyes. Thats all Im saying. If all you provide is what you know for a fact then its great info for everyone and apprecitated very much. In my experince with automotive over the years, its not a fact unless seen or done due to the mfg changeing and altering things as they come down the line without notice. Im not on here to look like a no it all or put things out to look like I am. I try to only say what I know as fact or otherwise I say, I think or this is what I found not sure if its fact. I dont want to add to the unknown here. Lets move on with facts known. Ok?

Outdoorsman no offense, but you may want to take it easy on Ken. He is here to help us, and from what I understand he has been closely affiliated with the design and development of QS at Delphi.

I would like him to return because yes what he says is fact! I assume that is why he has access to these drwaings and tech articles that are hard to come by. By the way Ken thanks for postings those.

Yes, accurate information is apprecitated for sure. As a matter of fact anyone reading this can go ask their GM service dept to print them any diagram you may want. It does not require any special knowledge or conection to get them. Ive done the same. I beleive many that read these posts may not have much experience with mechanics or limited experience and posting more information than required to answer a question my make matters worse for some or even cause them to spend money unnessasarily! The diagrams Ken posted both mentioned diffs as LOCKING and although the one diagram appeared to maybe be the correct one, it may mislead one to think the QS has a limiited slip locking diff which is not true to my knowledge. I did have the GM servie tech print the correct one for me the other day and no where does it say LOCKING on it as Kens did! Not picking on Ken. What you say about his knowledge may be fact. Why not ASSUME and just ask Ken what his credentials are? Im certainly not a GM certified mechanic but do have over 30 years of broad spectrum mechanical experience from aircraft (licensed for 28 yrs, jet,recip and radial), farm equipment and many types of auots! Assuming all information posted here is corect may lead to empty pockets. A wise individual will read the information, study it, ask more questions of others, analyze it even, before ASSUMING its corect simply because one thinks the POSTER knows all the facts without question! It is risky but to each his own. I for one always like opinions but make my own decession as to its accuracy. Tossing out questions on information is not an insult but rather a conformation of the facts my QS friend! ASSUMING, well, you know what they say about ASSUMEING? Offense is not intended toward anyone at any time. Carry on with the debates as they are very interesting.

Dave; thank you for your kind comments. The information I post based on my experience with trucks and published GM information. You may have noticed that on all my posts I refer to the source of information. As Outdoorsman said, you can obtain some of that information if you have contacts at GM or GM services. However, I know that not all of us have these contacts, and we may not be aware or can reach some information even we have the contacts; that is why I post when I see something relevant to our discussions. Thanks again.

Outdoorsman; you made me nervous so I checked my postings again.

Difference between two differentials is obvious. Limited slip utilizes clutches to bind the wheels, that is why wheels could spin when forced; no positive locking mechanism in the limited slip differential. Where as in locking differential there is a governor mechanism together with flywheels, latching bracket, cam plate and gear locks the wheels mechanically, no wheel spin, positive lock. The limited slip one, G86, is what I got in my truck, 2005, 2500 Yukon-XL.

I am hoping these will clear your mind. If you have any technical questions or comments, let’s discuss.

This message has been edited. Last edited by: Ken,

Ok Kenny, lets not read into posts whats not there! Friday night fight, bashing? Ive mentioned before about reading in emotions that are yours and not the posters! Read the words and try not to offend yourself by putting emotions of your own into the words of others. Ive been attaked by 2 of you on this forum already. Lets try reading not getting offended! If you look closely to your posting of the G80 rear you posted as the one the QS has it says at the top of the page LOCKING/LIMITED SLIP. Does it not? End of point! It may or may not be the one but my point is as Ive tried to point out more than once already to no avail, it says LOCKING/LIMITED SLIP even on your post! The one I got at GM does not say that anywhere on it. Sounds like your conections are the same as my own except did I pickup the fact your wife works for Delphi and thats your connection? You said your better part or something like that and I say that when talking about my wife! My truck is goint in for the replacement of the Limited Slip in the morning. Do not think it is going to fix the problem of the rear not even trying to lock inot limited slip mode. I do think there is a problem with the clutch pack though. Ive had it slip more than once as if the drive shaft was turning without the axle moving at all, then it will catch and go! I know im not happy with this so called Limited Slip and its by far the worst one Ive ever had in a GM truck. I may replace the unit again if I dont like the results. Ill do a bit more research before I make a choice on the one I would use but right now Im leaning toward the Detroit since it acts more like a limited slip should. I dont mind a little noise and sure dont want to spend over a $1000.00 for an electric one although it would be nice. Lets move on as Ive said already and now you reiterated that point!

Just to be clear, if I am one of the two you are referring to, I at no point was on the attack.

I was simply trying to help. Then I think we just had a mis communication on the explanation of wheel differential speed.

The help was offered because this subject is a sore spot with me also. I have always bought used. The first time in my life I was able to buy a brand new truck, and pick out what I wanted, I chose what I thought was top of the line. You would think after paying 50,000 for a luxury truck that I would not even know what the inside of the dealership looks like, but after three years of ownership I could tell you who is on shift at the garage.

I was so fed up I began to perform MY OWN service on a $50,000 truck still under warranty! Some days I think to myself I should of kept my old F150 at least the only thing wrong with that was the engine. Somedays that looks like an easy fix, compared to diffs, transfer cases, and mystical noises from underneath the truck.

I have seen the inside of MY diff and pictures of others, at this point many conversations on this board are scholastic, because I have had it apart at one time or another.

Outdoorsman I am sorry if we got off on the wrong foot. No hard feelings I hope. If there is anyone to be upset at,,, my opinion is it should be GM.

If the company I work for handled are customers in such fashion, there would not be to many big yellow earth moving machines out there.

This message has been edited. Last edited by: DAVECS2,

No problem Dave! We all have one thing in common, our trucks! Sounds as if the one problem on these trucks is the Diff. for some reason. After seeing the LS unit this morning myself, I can see whey they are acting up. Its a poor design in LS. The worst Ive seen. There is nothing to it! If this one does not work correctly, Im changeing it myself to a locking unit of some sort. I use mine in 4 WS mode when in 4WD on snow or mud where its slippery. It gives much better control of the truck that way! It can get real interesting quickly if you use the 4WS mode in 4WD! I think we are all good now. I think the soap box was getting in the way some times. Ill get back with more info once mine is done today. Im currious to see if it works any better. Ive not seen anyone else say they experienced what I did with mine. It would spin the drive shaft on occassion without moving then suddenly catch and go. This only happened for a second or two. Just as if you were sitting on a watermelon rhine and moving no where. I think the clutch packs were both slipping which gave it the spinning feeling and not moving? Maybe some new info will come out once the Tech gets it out and examines it closely. Ill be back!

Correction, I meant I use it in 2 WS mode when in 4WD! Sorry! The QS makes it too squirly in slick conditions.

Update on the replacement of my LS unit on my QS 2500 Crew 4x4. I dropped in to see the guts of the Diff during lunch today. The Tech said the oil was full of metal and clutch linings! I took one look inside the Diff. and imediately noticed the clutch plates were FRIED!!!!! No wonder I had no Limted Slip. This truck has been doing this since I ordered in new! This leads me to think that maybe some of you that have had DIFF gear problems may have had that problem due to the clutches going out and feeding clutch plates and lineings from them into your oil and knocking the bearings or even the Ring Gear and Pinion out! I was correct the Tech said, about the rear slipping as if the truck was not in gear at times when at stop lights! I agreed, as the clutch plates had obviously been slipping all the time, for a long time! Feels good to be correct and a Trained GM mechanic be wrong! The original Tech told me that could not happen! Ill post more if I can get a closer look at the old one after it comes out. I will add though, if anyone is thinking of installing a new Locker themselves, you better plan on a major breakdown. The process to get the axles out requires breaking down the entire steering mechanisim including the steering knucles in order to get the axles out!!!! Im sure some special tools are in the mix as well! It is not for the average shade tree mechanic for sure. There seems to be a clutch problem if they can get fried like mine with little use on the 4WD itself! More later. Dinner time!

Outdoorsman, that is good information to have. It is very fortuneate on your part that you found a dealership that was willing to do the work. I have raised a ruckus at two dealerships and niether has felt it necessary to crack the diff. That is why I did it on my own. I did not take the carrier out, but from what I could inspect, things looked normal, clutches were a little dark, but there was not alot of debris.

Of course I did not have the same problems as you. Mine was shuttering and what not. I wondered about how the axles would come out. They have had the king pins off my truck. They come off pretty easy. I had to have my outer bearings replaced. They were loose and leaking fluid. I guess there is a new design.

I am not sure what is involved in removing everything after the king pin. It will be interesting to see how well your truck works when it returns.

I agree with you on the quality of the diff. For the longest time, many members were swearing up and down that these were Detroit True Trac LSDs. I commented that if mine was it was really broken, because I have seen a couple True Trac's in action and mine functioned no were close to that. The True Trac is a helical Gear type LSD. Theoretically it should always work unless there is a catstrophic failure. After doing some research and finally popping my diff cover I came to the conclusion that the QS is just using old D60 run of the mill LSDs. These did not function that well when they were introduced, much less in today's applications.

So are they going to let you keep the old LSD. I would maybe be interested in it. If I could develop a clutch upgrade for it, that may be an economical solution for us QS guys.

I had to call GM myself to get this covered under GoodWill Warranty. It took some doing but they are taking care of it! I just came back from the Dealership and they have it all apart and ready to go back now. Its going to be a 3 day repair looks like. The steering knuckles are completly loose on top and bottom, then they just pulled the axles out far enough to get the LS carrier out. I doubt they will let me have the old unit. I figured they would have to send it to GM or something. Ill ask just in case. This thing as the funkiest emergency brakes Ive ever seen too! They are seperate from the disc brakes and have little mini brake shoes. They said they have had problems with people burning them up too! Cant imagine how unless they move with the brake on! King pins actually go all the way through a spindle and axle to create the pivot point and except for bigger trucks, Ive not seen king pins since the really old days of solid front axles. Ive replaced a few in the old days. Not an easy task either if they have been in there for years! Ill post more as I get more.

Yea your right they really are not king pins. The setup kind of reminded me of the setup on my Twin I Beam ford, so I kind of leaped to the king pin thing myself.

As for the Brake shoes, that has been GM's bad idea since about 98. They are also partially the reason I needed the end bearing assemblies replaced. I had grease exiting from the bearing assemblies on to my parking drum. I had to put my brake on so tight to hold that it was not fully releasing.

GM's mini drums also make for a pretty expensive back rotor.

After reading this thread I am convinced that these differentials are junk, due to poor design. I think we should file a class action law suit against GM and Dana, on behalf of all QS owners.