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  #1  
Old 01-06-2000, 11:04 PM
Tim_K Tim_K is offline
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Ok, time for another technical article, this one about Sure-Grip rebuilding. This is for cone-clutch 489 cases, not the earlier style Dana/Spicer 742 cases. I don't have the magazine articles here with me, so I'm doing this from memory. I'll reread them and post an update next week. High Performance Mopar had finally published a good tech article, I thought (genius level for them), until it became obvious they hadn't quite thought it through as much as possible. Shortly after the first article, the writer answered a question in a letter to the magazine about the side gears moving too far away from the spiders. His response was that "He works on big trucks during the day, and it doesn't hurt THEM!" Well, we're not talking about trucks here, are we? Alrighty then.
Mopar Action also wrote about this problem, but I was surprised that they didn't suggest the obvious fix. They were too busy talking about the new $300 or so 30% stronger differential which has a one piece case so you can't take it apart when it wears out, you have to buy another one. How did they machine and assemble it in a one piece case? I don't know, but I'd rebuild 10 old ones before I bought 1 new one like that.
So what did I do to fix the side gear problem? Simple: Shim them back in! You just have to be darn careful with your measurements to get the right thickness shim. Too tight and it might mess up the gears and not let it unlock for turns. Too loose, and it won't do any good, either. Here's what I did.
I know this one guy who is a machinist, he has a lot of machining tools at his home, too. Many different kinds of micrometers, which were useful. I took the Sure-Grip to him and showed him what I wanted to do and how to do it. After laying each case half on a flat surface and measuring the height of each cone clutch (inner flat surface next to side gear) and seeing that each had the 1/2" or so rub mark on the outer edges, we cut 0.060" off the outer edge of each cone. after carefully reseating them, we remeasured their new depth. We also now had 0.040" clearance between the case and cone (outer flat side). Each had dropped 0.020" down in the case, with the clutch surfaces now touching. To allow for wear (before and after I rebuilt it) I decided on a 0.035" shim thickness for each side. Went to a local metal place and got some 0.035" thick stainless steel. Went home and cut a donut shaped piece for each side. Donut piece goes between the cone clutch and side gear. Reassembled Sure-Grip, but without the springs and plates in the middle. If you reach your fingers in the middle, you can push up on the side gear and watch how far it falls back down to engage the spiders fully. I had about 0.020" or so clearance on each side gear. So, that part was done.
The article said to add springs if you want more pressure. This would come in handy on snow and ice, where the wheels would spin before much torque was generated to push on the cone clutches. I added 4 high gear clutch pack springs from a 727 transmission someone else had taken apart. They fit inside the original springs just right. Reassembled Sure-Grip and put it in the car.

Did it work? Yes! The old Sure-Grip, before it was rebuilt, would work, but it wasn't very sure. If both tires were on dirt, they were ok, but one tire in dirt and one on pavement, forget it. Now that it was rebuilt, it locks up VERY well! One tire on ice or mud, the other on pavement? Pavement tire spins immediately. Tried it on both tires. Many times. A successful operation.

Now, with 0.040" clearance, I don't know how long it will last. One guy I talked to at Auburn Gear said they built them new with a tolerance of between 0.010" and 0.050" clearance. But I think I could have gotten more reliable information from a brick wall. I rebuilt it back in the spring and put it in my Valiant with 3.23 gears. Soon took it out. 3.23's were too much for my highway speeds with a /6, and I didn't really need a Sure-Grip in it for the summer. See my article 'My first torque converter failure' for more information on this. So I decided to 'save' it for this winter. Just put it back in on New Years' weekend, and so far so good. Have been giving it lots of excercise in icy parking lots.
Well, I'll have to review the articles this weekend, and since I'm in a library typing this, some ugly retard is rushing me for his turn on this computer. So, I'll add more later, and I'll be looking forward to seeing your responses on this.
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  #2  
Old 01-06-2000, 11:33 PM
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Christopher Christopher is offline
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Sounds good to me Tim.I read the same 2 articles and thought there were a few things left out.I've got a Auburn unit to pull down,it was in my Demon when we had the 8 3/4" installed and it broke on a burnout,so I don't know whats wrong with it yet.
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Old 01-06-2000, 11:52 PM
Elwenil Elwenil is offline
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Ok, that was an excellent tech article, Tim_K! Here's a question for ya'. Rebuilding is fine if your Sure-Grip is worn, but what if it's physically broken? I have a factory Sure-Grip out of my 88 W150 that has the spider gears torn out. Seems M/T 39's are a bit much for the factory deal to handle. Anyone know where to get replacement gears for them? Auburn Gear was the OEM supplier for this one, but they won't sell the internal parts. I think Dana makes replacement parts for their OEM Sure-Grip, but I don't think they will work, dur to design differences. Any ideas? By the way, I replaced my Sure-Grip with the aftermarket version of the Auburn Gear Limited slip unit. It was $300, but still cheaper than the Mopar one from the dealer. I'd like to rebuild the old on to go in my Ramcharger. It only has 32's so it should handle it ok.

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~Elwenil~ ~.\|/.~
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72 Charger SE
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Old 01-07-2000, 08:45 AM
V10nacuda V10nacuda is offline
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This same rebuild worked for me & I didn't shim the gears. So far 1 season in my 3900# barracuda 3.91's w/slicks 12.30@108...The pig was out of a 150,000mi 71 imperial w/3.23's.. removed the sure grip & placed it in a junk yard 3.91 gear set. works great hardly any whine..Best part was it is CHEAP!!!!!!!!!!
my 2 cents
V10
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  #5  
Old 01-08-2000, 05:34 PM
Tim_K Tim_K is offline
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Ok, here are the magazine articles I referenced in the first posting.
The May 1997 High Performance Mopar contains the original article.
The June 1998 Mopar Action is the one that says not to do it, just buy a new one. They also didn't think of the shim idea like I did. The STONE AXLE article begins on page 52, and the important part is on pages 58-59.
The September 1998 High Performance Mopar issue, in its "Knucklebustin'" column, is where Ted Wagner tries to explain why he didn't think of the shim idea before he wrote the article in the first place.

Well, whatever. I took their information, modified it to suit my purposes, and it has worked very well for me.

Elwenil, if that one Sure-Grip unit you have has broken parts, I wouldn't even mess with it. Junk it and find another one to rebuild.

As an additional note to the durability question, here's another example. A friend of mine has a '70 Dart Swinger, original 340 car but now with a 318, 4 speed, and 3.91 gears. He runs 13.6 at 100 mph in the quarter. Also does a lot of high rpm, bounce the tach off 7000 rpm shifts. Spins tires on every gear change. We took apart his Sure-Grip for a rebuild when we were building the car. Not only were the cone clutches worn on the outer 1/2" of contact surface, they were worn all the way to the middle! Someone who had it before just didn't know when to quit trying to make it work. Anyhow, he had 0.080" cut off each cone, shimmed in the side gears, I think the same 0.035" as me but I'm not sure, and assembled it. It worked great all last year and still does, about 7000 hard miles on it.
Once again, I look forward to any responses with your ideas on this.
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  #6  
Old 01-08-2000, 06:56 PM
PRO PRO is offline
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great info Tim,I've never considered rebuilding a non rebuidable but who said the impossible isnt possible?One note though in a truly fast car I wouldnt experiment with my life,dont get me wrong I will definitely use your method of rebuilding on my 4x4 but not on my 11 sec car,why? because an unforeseen failure could cost me my car amd life and maybe somebody elses.Heres a hypothetical example,I,m staged at the line waiting for the lights at 6000rpms,I cut a better ;light than my opponent so I get out first,tires off thr ground,I grab 2nd at the tree and boom the diff explodes and locks the rr tire and sends me into the other lane taking out my opponent,and heres the kicker...he's riding a motorcycle !!So lets find a virgin suregrip and get the factory measurements so we know just what the original manufacturer/designer had in mind,anybody out there have a NOS suregrip or even a known low low mileage one? I'd love to see what its specs are.my guess though Tim is that your so close it doesnt matter its just I dont want to risk anything,I always remind myself going fast is fun and its not worth endangering anybodys life over(although is always a risk to some degree but so is bathing). Mopar guys are smarter and your proof!!!!....PRO...
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  #7  
Old 01-08-2000, 09:10 PM
Larry S. Larry S. is offline
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Great post Tim, thanks! This one is going into my file for future reference.
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  #8  
Old 01-08-2000, 09:51 PM
MopART MopART is offline
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Thank Goodness !! Finally found an *active* Mopar site that can help. All this talk about rebuilding the SG and I don't even know how to positively, absolutely identify one if it was lying on the ground. I installed one into the 8 3/4 in my Scamp, but never thought to eyeball it for future reference. Now I need to find a SG unit for the Challenger. Hope you guys can help. Then I can use all this good info to make sure it's in good shape.

MopART -
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  #9  
Old 01-11-2000, 12:57 AM
Tim_K Tim_K is offline
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MopART:
If you can get any of the magazine issues with the Sure-Grip articles, they will put you well on your way to identification, as well as how they work and many other things.
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  #10  
Old 07-03-2000, 07:56 PM
Tim_K Tim_K is offline
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Well, here's an update for this article I wrote long ago. The Sure-Grip is still doing very well, but I made a change. About 2 months ago, I changed back to 3.23 gears in my Valiant from 2.76's, and at that time I decided to take out the extra springs. I had gotten very tired of all the popping, crackling, and grabbing sounds the Sure-Grip would make if you were going in any direction but straight ahead. Parking the car in a parking space was the worst, even at slow speeds if you were turning at all the noise was there. So after I took out the extra (727 high gear clutch pack) springs, I reassembled it in the stock way, and now it is very quiet and still locks up good.
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Old 07-03-2000, 07:57 PM
Tim_K Tim_K is offline
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Well, here's an update for this article I wrote long ago. The Sure-Grip is still doing very well, but I made a change. About 2 months ago, I changed back to 3.23 gears in my Valiant from 2.76's, and at that time I decided to take out the extra springs. I had gotten very tired of all the popping, crackling, and grabbing sounds the Sure-Grip would make if you were going in any direction but straight ahead. Parking the car in a parking space was the worst, even at slow speeds if you were turning at all the noise was there. So after I took out the extra (727 high gear clutch pack) springs, I reassembled it in the stock way, and now it is very quiet and still locks up good.
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  #12  
Old 07-04-2000, 05:08 PM
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Brian_wo Brian_wo is offline
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Dana power-loc

<img src=http://www.geocities.com/MotorCity/Shop/3978/suregrip.JPG>
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