sure grip rear end

MarsMonster · Post by **MarsMonster** » Fri Jan 27, 2006 8:58 pm

Hello,

I have a really stupid question. I have a 3:55 rear end in my truck, and I am able to burn both tires off even with a load of bark in the back. Both tires seem to spin wildly. I am under the impression that I don't have a sure grip rear end because I was told that I don't.

I questioned the fact and jacked my truck up to see if I could spin both tires in the same direction. I was told that if you have a sure grip rear end then both tires will spin in the same direction when you spin one tire with both off the ground. Is this true?

Also I am looking at a photo of a sure grip rear end
here on ebay and mine looks similiar.

http://cgi.ebay.com/ebaymotors/New-1969 ... dZViewItem

What gives? Why am I able to spin both tires off to the point that my whole truck wants to go side ways.

Thanks,

Mars

Hemikuda71 · Post by **Hemikuda71** » Fri Jan 27, 2006 9:06 pm

Yes Mars, when you jack the truck up and put it in neutral and spin one tire, if both spin the same way then you have a sure grip. if they spin opposite of each other then you don't have a sure grip. I hope this helps.

Jeffc · Post by **Jeffc** » Sat Jan 28, 2006 12:34 am

Hard to tell the cases appart because they all look pretty much the same sure grip or not.
Cases are ID'ed by last 3 numbers of numbers on side of case. 741, 742 and 489, last 2 are the best but all are good.
Yes, if you turn one, both turn the same way if suregrip.
The tag will have a "s" on it if there is still a tag on one of the studs with the gear ratio, some will also have a "s" stamped on the bottem (but not common).

2 types of suregrips were/are made, one cone and one clutched, the clutched dana is the better of the two and is a easy rebuild. The cone Aubern type are great till they get worn out, almost impossable to rebuild and
never work as well new if rebuilt.

MarsMonster · Post by **MarsMonster** » Thu Feb 02, 2006 8:39 am

Ok, I jacked my truck up again and spun the back tires while in neutral. I found that for a time they both spun in the same direction, but other times they did not.

I also noticed the same thing with the transmission in park. It also depended on which tire I would spin. It seemed to me that both tires would spin in the same direction if I spun the passenger side rear tire. While in park.

If I spun the driver side rear tire in park or neutral then only one tire would spin, or I could only get the other tire to spin in the same direction going in reverse not forward and reverse.

Never having seen how a suregrip should behave before when you jack the truck up and spin the tires I am not really sure what I am looking for/at.

By the way the rear that I am talking about is an 8 3/4" rear end 3:55 gear set in a 742 case. It is an open gear set.

Any insight would be appreciated.
Thanks,
Marks

mesman · Post by **mesman** » Thu Feb 02, 2006 8:49 am

You're able to spin the tires with the trans in PARK? I thought the wheels would not spin in park!

MarsMonster · Post by **MarsMonster** » Thu Feb 02, 2006 8:51 am

I can spin the tires in park yes. The drive shaft does not turn but the tires do, and they both spin in the same direction.

digdoug · Post by **digdoug** » Fri Feb 03, 2006 8:21 pm

What do you mean when you say "they both spin in the same direction"?

MarsMonster · Post by **MarsMonster** » Fri Feb 03, 2006 9:02 pm

I think I made a mistake when I checked. I jacked up both back tires. I should probably have just jacked up one side, put the car in neutral and see if I can turn the tire.

I jacked up both back tires and spun them, to see if they both moved forward together.

MarsMonster · Post by **MarsMonster** » Fri Feb 03, 2006 9:47 pm

Ok, I am pretty sure that I don't have a sure grip. I just got back from jacking the passenger side of my truck. I then put the truck in neutral to see if I could turn the jacked up tire and it turned easily.

Mars

Website · Post by **wideblock** » Sat Feb 04, 2006 12:17 am

another possibility is that you do have a sure grip but its worn to the point that it will let go and behave like an open diff on occaision. an open will not spin both tires at once on pavment, it might go back and forth swapping tires, but it will only do one at a time.