Sure grip issue

[70 Sport Suburban]

Ok hopefully i can explain this the right way my 70 Wagon was supposed to be a open 3.23. Well last night i pulled the gears found out it was a 2.76 open 489 case. I got a set of 3.91s sure grip 489 case from a friend of mine put them in if i have the wagon in the air everything is fine. Wheels spin forwards and backwards no noise when i put it on the ground you feel it shift into gear but give it gas it won't move and makes a lond screaming noise. The driveshaft does spin when it is on the ground anyone ever have a issue like this before?

 

[70 Sport Suburban]

And also a buddy gave me his 741 case 3.91s and it does the same thing.

 

[Davea Lux]

Your clutch pack is probably burned out or seized. Did you put the correct oil in it? Sure grip can not be run with standard gear oil requires the special sure-grip mopar oil or equivalent.

Dave

 

[Big_John]

Ok hopefully i can explain this the right way my 70 Wagon was supposed to be a open 3.23. Well last night i pulled the gears found out it was a 2.76 open 489 case. I got a set of 3.91s sure grip 489 case from a friend of mine put them in if i have the wagon in the air everything is fine. Wheels spin forwards and backwards no noise when i put it on the ground you feel it shift into gear but give it gas it won't move and makes a lond screaming noise. The driveshaft does spin when it is on the ground anyone ever have a issue like this before?

And also a buddy gave me his 741 case 3.91s and it does the same thing.

So... If I'm reading this right, you've had two different carriers in the rear and it makes the noise with both of them??

Did it do this with the old (2.76) carrier?

 

[Davea Lux]

So... If I'm reading this right, you've had two different carriers in the rear and it makes the noise with both of them??

Did it do this with the old (2.76) carrier?

They both have bad clutch packs if the drive line turns and the car won't move. The clutch packs on a lot of used rear ends have this problem, which is why they are not still in the car they came out of.

Dave

 

[70 Sport Suburban]

Your clutch pack is probably burned out or seized. Did you put the correct oil in it? Sure grip can not be run with standard gear oil requires the special sure-grip mopar oil or equivalent.

Dave

So i didn't have a sure grip addictive i put in a 75w90 full synthetic gear lube only ran a few times trying to figure it out. A buddy said i should put a staright 90 with the sure grip addictive and leave it off the ground and let it spin. The 489 3.91s came out of a 71 GT my friend had so I've seen them used but have been sitting for maybe 4 or 5 years and he regularly lubed them up.

 

[70 Sport Suburban]

So... If I'm reading this right, you've had two different carriers in the rear and it makes the noise with both of them??

Did it do this with the old (2.76) carrier?

Yes two different 3.91s sets and same problem i drove my car last night with the 2.76 and put the other gears in last night after driving it. I haven't put the 2.76 back in yet and try them.

 

[Davea Lux]

It is possible that the synthetic oil you installed is incompatible with the clutch material in the 741 cased sure grip, Synthetic oil did not exit when these clutch frictions were designed. The synthetic oil might be "too slick" for the clutch frictions to get a bite. You can try putting in conventional oil with the sure grip additive, but I still suspect you clutch packs are burned out.

Dave

 

[65sporty]

I think you problem is something else besides clutches, the clutches are there just to spin both wheels, if they are bad it should still move the car just act like a open. With both wheels on the ground the spider gears turn the axles to move the car and the clutches keep the axles from slipping turning both wheels. If the clutches were bad it would move but you would get a one wheel peal just like a open.

 

[67Monaco]

1st, why did you yank the 2:76's was there a reason?

2nd, where is the loud screaming noise located?

 

[70 Sport Suburban]

1st, why did you yank the 2:76's was there a reason?

2nd, where is the loud screaming noise located?

I was looking for a sure grip and my friend had a set that's why i pulled them no issues i actually drove it a hour before pulling the gears.

Last night my friend came over we set the car on the ground and put it in gear and the driveshaft spins and doesn't move the car we lifted up the pass wheel and the axle was moving with no weight on it. Sound was coming from the rear like the axles are trying to spin but wont engage.

 

[70 Sport Suburban]

I think you problem is something else besides clutches, the clutches are there just to spin both wheels, if they are bad it should still move the car just act like a open. With both wheels on the ground the spider gears turn the axles to move the car and the clutches keep the axles from slipping turning both wheels. If the clutches were bad it would move but you would get a one wheel peal just like a open.

Both sets of gears came from friends that used them before neither can believe that 2 sets both went bad out of nowhere but anything can happen.

 

[Big_John]

I think you problem is something else besides clutches, the clutches are there just to spin both wheels, if they are bad it should still move the car just act like a open. With both wheels on the ground the spider gears turn the axles to move the car and the clutches keep the axles from slipping turning both wheels. If the clutches were bad it would move but you would get a one wheel peal just like a open.

Since the 489 center section probably has a later sure grip, here's a rebuild of the later "cone style" sure grip. You can see how the spider gears fit into the carrier and the cones act to restrict the carrier from turning like it would if it was an "open" rear. No friction material, although the metal cones wear and then bottom out. They don't function like a sure grip then, but they will still work like an open rear.

How To Recondition a Sure Grip Cone

We had a local guy that would rebuild these many years ago, before anyone else did. He would increase the spring pressure so the cones had less slippage. Quite a few of us used these in drag cars back when we raced classes that didn't allow spools.

 

[Big_John]

I was trying to find a good breakdown of the earlier sure grip, but my bookmarked link was gone. I did find this...

https://www.bigblockmopar.nl/wp-content/uploads/2011/03/MoparSureGripManual.pdf

This explains how it all works and you can see the difference in operation of the two styles.

 

[Yatzee]

Ok hopefully i can explain this the right way my 70 Wagon was supposed to be a open 3.23. Well last night i pulled the gears found out it was a 2.76 open 489 case. I got a set of 3.91s sure grip 489 case from a friend of mine put them in if i have the wagon in the air everything is fine. Wheels spin forwards and backwards no noise when i put it on the ground you feel it shift into gear but give it gas it won't move and makes a lond screaming noise. The driveshaft does spin when it is on the ground anyone ever have a issue like this before?

If this is a "posi" there is a small slug of metal at the end of the axles that releases the clutch pack as you corner. As one axle moves inward on a corner it pushes on the pin and releases the clutches. I once attempted to pull the axles on a 489 "posi" only to find the pin was welded to the ends of both axles from severe heat due to low fluid.
You may be hearing the pin wining especially if you did not reset the axle endplay.

 

[Snotty]

I did not read the previous responses, but I had this happen when I put an A Body 8.75 rear into our Gremlin, running a 3.55 SG. Lots of noise and a little go. Turns out the axles were too short to engage the SG pack. When I swapped it for a 2.76 open, car ran great! Once I got longer axles all worked great.

 

[70 Sport Suburban]

I did not read the previous responses, but I had this happen when I put an A Body 8.75 rear into our Gremlin, running a 3.55 SG. Lots of noise and a little go. Turns out the axles were too short to engage the SG pack. When I swapped it for a 2.76 open, car ran great! Once I got longer axles all worked great.

That what my friends are thinking also when i slide the axles in they don't pop in until its close to the backing plate. I thought it should be a little farther out but im glad to be part of this group always helpful im heading to a yard this Friday lots of c bodies gonna pull some alxes. And try everything that you guys commented.

 

[Davea Lux]

That what my friends are thinking also when i slide the axles in they don't pop in until its close to the backing plate. I thought it should be a little farther out but im glad to be part of this group always helpful im heading to a yard this Friday lots of c bodies gonna pull some alxes. And try everything that you guys commented.

Since you already have your old rear end and the first one you tried, measure the width of the axle capture point on both carriers, if your 2.76 is wider, you have identified the problem, the axles are too short. That probably means that both of the 3.91 rear ends were out of something other than a C-Body as the sport suburban uses C-Body axles which should mate up to a C-Body carrier. Other axles are not going to help if you have a B-Body carrier installed in a C-Body housing. You will need to find a C-Body carrier.

The other issue is that you are going to beat your engine to death running a 3.91 gear set at highway speeds. A 3.23 set came standard for that reason.

Dave

 

[Darter6]

SOME sure grips had 2 piece spider gears and the axle won't in-gauge, AKA the axle is too short for the 2 piece spiders.Not a problem with a open rear.
Dr.Diff sells the one piece spiders. I did this with a 65,Same as you, put it together, backed out of the garage,put it in park and watched it roll down the driveway. The axles were in just enough to move the car,but couldn't keep the weight from it rolling away. Dr.Diff told me that many of us learn the hard way.Hooked me up with the right parts and no more problem.Look him up,he is on the net.

 

[twostick]

If this is a "posi" there is a small slug of metal at the end of the axles that releases the clutch pack as you corner. As one axle moves inward on a corner it pushes on the pin and releases the clutches. I once attempted to pull the axles on a 489 "posi" only to find the pin was welded to the ends of both axles from severe heat due to low fluid.
You may be hearing the pin wining especially if you did not reset the axle endplay.

That pin's sole purpose in life is to maintain the tapered wheel bearing end play. It is called a thrust block.

It has nothing to do with the Suregrip function.

An axle converted to sealed Green bearings does not need the block and it is usually removed.

Kevin