8.75 SureGrip , Is this Normal?

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70Hardtop

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I just put a 3.23 SureGrip (741 case) centre into my 340 Hardtop. This centre had previously had new carrier bearings fitted and the unit bench checked for normal operation.

With the car on stands and no drive shaft fitted, I noticed some things, can anybody who knows these 8.75 centres tell me if these characteristics are correct please?

With just one axle in (RH side), the axle turns easily with a loud noise coming from inside the housing, like a clicking sound. Nothing else turns. I expected the input part (yoke) to turn also.

With both axles fitted, when one axle is turned, the other axle turns the opposite way. (I thought that Limited Slip diffs should turn the same way, I thought only open centres (non-LSD) turned in opposite directions? Also the yoke does not turn.

Now when the yoke is turned (it is very stiff, it needs a lever to be able to turn it), both axles turn the same way, but can be stopped with your hand, even though the yoke is turning. Is this the LSD clutches or cones working?

Are all these characteristics normal?

Thanks for your help
 
The older 1s up to 1966 I believe never had a bevelled disc in the unit (clutch type) for preload and will spin opposite when in the air. But under no circumstances should it be clicking. I would pull it back out and post up some pics. Kim
 
sound like a broken auburn type , they break . dana type is much better .
thank you for that reply but it means nothing to me. Same as the first reply. If you read the post you would have read that it has had new carrier bearings installed and obviously at that time would have been checked to see if it was "broken" !! Of course "Dana types" are better. That doesn't help me in the slightest with my problem does it?
 
The older 1s up to 1966 I believe never had a bevelled disc in the unit (clutch type) for preload and will spin opposite when in the air. But under no circumstances should it be clicking. I would pull it back out and post up some pics. Kim
Thanks for the reply Kim. What photos will I take of it? Do you need to see what year it is? Will that be in the casting numbers or a stamp somewhere? I thought this would have had cones, not clutches. Someone also told me that they think there is too much preload set in. Thanks
 
''Peg leg'' is slang for a single track or non sure grip differential.
I think that the input yoke on the differential should turn by hand with the wheels in the air and the drive shaft unhooked.
It sounds like it's binding if you need to use a tool to turn it.
 
if you can not spin the yoke by hand, pinion or carrier or both bearing preload is too tight. did the carrier look like a sure grip? cuz it is acting like an open diff, or a completely smoked sure grip
 
''Peg leg'' is slang for a single track or non sure grip differential.
I think that the input yoke on the differential should turn by hand with the wheels in the air and the drive shaft unhooked.
It sounds like it's binding if you need to use a tool to turn it.

Thanks for the explanation Dartnut - now I know! Mine is definitely an LSD though. Unfortunately I will have to pull it out again and check it. I think it has clutches, not cones, because it is all closed up and no springs visible. Maybe the clutches are well worn. Hopefully the service manual can guide me, maybe even someone has done it on YouTube.
 
if you can not spin the yoke by hand, pinion or carrier or both bearing preload is too tight. did the carrier look like a sure grip? cuz it is acting like an open diff, or a completely smoked sure grip

Thanks Marco, someone else also suggested the preload may be too high. Yes it is definitely a SureGrip, it has the closed-in clutch pack, with the bolts around the extra part on the crown wheel. I have seen a picture of the cone type ones (Auburn style) and they have the visible springs. This one doesn't.
The place that did it years ago has gone bankrupt and I can't vouch for his skill in diffs! But the carrier bearings were replaced, however that doesn't mean he looked at the clutches. They may be the original ones and may be worn out, or like you say, smoked. All this time sitting on my shelf, clean and nicely wrapped in plastic, here's me thinking it is a good centre.
 
Yeah, I agree that something is not right. No diff should ever require a bar to turn the pinion! So it has to come out. And since it "peg-legs" it's either not a well-functioning Chrysler SureGrip, not a SureGrip at all, or an RPM-sensitive "posi" or a screw-gear type of aftermarket LimitedSlip.
I have never seen an RPM-sensitive "posi", that is a GM thing. .
And the Screw-gear types are very rare and expensive.
I have also never seen a Chrysler-type suregrip pegleg on jackstands, but I suppose a binding pinion could do that. So your unit has at least two problems,neither of which can be addressed until it is on the bench. Sorry :(
 
Yeah, I agree that something is not right. No diff should ever require a bar to turn the pinion! So it has to come out. And since it "peg-legs" it's either not a well-functioning Chrysler SureGrip, not a SureGrip at all, or an RPM-sensitive "posi" or a screw-gear type of aftermarket LimitedSlip.
I have never seen an RPM-sensitive "posi", that is a GM thing. .
And the Screw-gear types are very rare and expensive.
I have also never seen a Chrysler-type suregrip pegleg on jackstands, but I suppose a binding pinion could do that. So your unit has at least two problems,neither of which can be addressed until it is on the bench. Sorry :(
Thanks very much AJ for the info, yes I will pull it out soon. It is definitely an LSD but as you say, behaving like an open centre. I paid A$200 for it (about US$165) for it but as I mentioned, spend another A$300 on bearings and labour. So I assumed it was a decent unit. With one axle in (RH side), that turns very easily by hand, but the yoke doesn't turn, so it maybe a binding pinion. I can only say more once it is out. Thanks.
 
If you turn a suregrip round with only one shaft in the axle, the splines in the suregrip unit will be misaligned so when you put the other shaft in it wont bottom out/fully seat the way it is supposed too. It is possible thats what happened. Both shafts should slip in and fully seat without force. To align them again you will have to put one axle in fully seated. You will then have to put the other shaft in as far as it will go and then use a pry bar and turn that shaft and push it in at the same time. This takes some strong force. I've done it. Let me know if you dont understand.
 
Thanks for the info Trebor. I have the RH axle all bolted in and the LH axle seems to slide in ok (although I have not bolted it right in tight yet). What you describe, sounds like there are two concentric splines on each side. So luckily I have another 8.75 Suregrip out of a car that I can look at and yes, on each side I can see two concentric spline tubes - but whether they can rotate independent of each other (on one side), that I don't know. If one axle is all the way in, I cannot see how the other side splines could be misaligned, unless that axle was only put in part way and only accessed the outer spline section and was turned, while the inner spline stayed still. I am not sure they would rotate independent of each other. However I will check carefully when I do this. If a pry bar has to be used, does this mean that each concentric spline tube is locked in somehow to a spring mechanism? That is the part I am not sure of, but until I try it I cannot really ask more.
 
I think you got the right idea.
Maybe you left a rag in there and it got jammed in the ring gear. Or something like that.
Once the pinion won't turn, then turning the axle one way on one side, HAS to turn the other one in the opposite direction. It HAS to. But in a cone-type SureGrip, it should take about 130ftlbs of force to do this.
And like you say, there are two parts on each side that the axle has to engage; the outer one is the sidegear, and the inner is the actual clutch, on each side. They (all 4) are normally aligned by the assembler.
The trac-lock can be set up a little looser, cuz it operates a wee bit differently. The cross pins are driven up ramps by the driveshaft (OK by engine torque), which increases the clamping force. I still set them up about the same.
But the pinion should rotate fairly freely,in any case.
 
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Thanks AJ, interesting about the differences. and I'm glad you said about the directions of rotations. Hopefully that means mine is behaving normally. But just too stiff. Don't forget it has been sitting dry on a shelf for about 3 years. Although I would have liked to have thought that the guy who did it used assembly lube ! I will know more after this weekend. I am leaving it installed and am filling it with oil and trying to work the oil all through it and will be turning the yoke/pinion as much as possible to try and free up whatever it is inside that is stiff. But without a running engine to keep it running up on stands, doing it by hand for any length of time will be a workout.

PS, definitely no rag in there!!
 
Don't forget it has been sitting dry on a shelf for about 3 years.

That, in of itself, could be part of the problem. It is dried out and any gear oil is dried up a bit making it stiff to turn.

Don't forget friction modifier once you are ready to actually run it.
 
It's a required ingredient. Any suregrip must have the friction modifier.
OK, I'm not sure...is that the LSD additive that is required when using standard gear oil? Because i am using an 85W-140 high quality transmission/diff oil that states it is for use in LSD's (In Australia, LSD is just the blanket term for Limited Slip Diff, applies to all makes of car). Or do I still need to add this friction modifier because it is a Sure-Grip?

Question # 2: The oil is in and I rigged up a small bar on the yoke to make turning by hand easier (no engine in yet). It is now a lot easier to turn but still not turning freely, and when I turn the yoke, the wheels both turn the same way, like before. BUT, the same problem is still there, with both axles bolted in, when I turn one axle, the other turns the opposite way, like the sure-grip part isn't working at all. Also, when the yoke is turned, either wheel can be stopped with just one finger, there is no solid gear connection. Is that normal? I think maybe the clutches are fried, or just so worn that nothing is happening, and it has gone back to behaving like an open centre. If it hasn't been touched since new, this is highly likely, esp as I don't know the history of it.

thanks
 
OK, I'm not sure...is that the LSD additive that is required when using standard gear oil? Because i am using an 85W-140 high quality transmission/diff oil that states it is for use in LSD's (In Australia, LSD is just the blanket term for Limited Slip Diff, applies to all makes of car). Or do I still need to add this friction modifier because it is a Sure-Grip?

Friction Modifier is required on top of gear oil. What friction modifier does, is actually kinda opposite of what you might think. It allows the clutches to slip some during normal driving conditions which allows longevity.
 
Bad plan man!
Something is physically preventing the pinion from turning,and I believe it is one of the cones or axles.Consequently when you force the pinion to turn, you are forcing both clutches or cones to slip and the side with the least friction turns.The resistance you are feeling may be the clutches. It may also be in the pinion but I think IIRC that you said with no axles in, the pinion turns normally?
Something is preventing at least one axle from turning freely. If you assemble it this way and drive it this way, I'm pretty sure it will burn up.
Again, this is not normal.
Also the friction modifier goes in with all/any EP oil, except one that is marked specifically for SureGrip(LSD) units,which should already have the modifier in it;read the fine print. When in doubt slam it in there.The SureGrip is just Chrysler's name for a type of LSD, of which there are maybe 4 or 5 types, not all of which are made for Chrysler products
 
Bad plan man!
Something is physically preventing the pinion....

I'm not sure why the pinion is stiff, I don't think it would be foreign matter, but as I said, now with oil all around it, it is a little easier. However it still behaves like an open centre. And no, with it out of the car and no axles, it was still super tight to turn. With both axles bolted in, and turning one axle, the other wheel turns opposite (like an open, non-LSD centre) and the yoke does not turn. (unlike the BorgWarner LSD in my Valiant, the yoke will turn when you turn one wheel). Also, when another person turns the pinion, either axle can be stopped with one finger pressure! I did an experiment -see pictures. I have another 8.75 (489 case) with a Sure-Grip -but this one is the BorgWarner cone style whereas the faulty 741 is a clutch, Dana style type. I know that one is good. I stuck axles into it on the ground and did the same checks -totally different ! The yoke is easy to turn with two finders. Turning one axle will turn the other axle the same way, and when the pinion is turned, the axles are locked into gear, they cannot be stopped with force.

So it has to come out. My guess is that the clutches are fried, non operational, and that the guy I bought it from (who also did the carrier bearings) may have known this, I think he tightened the preload too much. And here in Australia, these 8.75 centres are not easy to find. Hardly ever see them for sale and to fix this one with a new LSD unit (eg Auburn Gear or Nitro posi) with the install kit and shipping etc is about A$1400-$1600.

489 Sure-Grip BorgWarner LSD centre.jpg


71 Chal 8.75 489 case.jpg


testing SureGrip in 489.jpg
 
What does that mean? Sorry, that is a meaningless answer to me.
After reading a handful of your responses I've come to one conclusion... you're a dickhead.
Maybe you should see someone about that.
Questions are key, when you don't know...you ask and ask again for more detail.
"Meaningless answer to me" is your problem,again, because you're ignorant. Its not the person trying to help you...
 
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