How to find out if I have sure grip or not ?

[christianlarsen]

Hi.

All i know about my 69 charger's rearend is that it is 8 3/4. How can i identify if it is sure-grip or not ?

[Ghoste]

Jack the rearend up so both wheels are off the ground and turn one.  If the other side rotate in the same direction, it is probably a limited slip.  A backup method would be to pull the drain plug on the side and try to look in there with a small light and verify that the Sure Grip unit is in there.  The jack and rotate method is pretty easy, not failsafe, but almost.

[aifilaw]

well, I'm sure you can check codes on the build plate...but even then you don't know if the clutches are still good....

easy way to check, jack up the entire rear of your car, put the tranny in neutral, grab a tire and spin it. if the other tire spins in the same direction then you have a sure grip(also known as a limited slip or posi-trac). If the car is in park (driveshaft is locked) then the other wheel will spin the opposite direction at the same rate.
while your there you could spin the tire around 1 time and count the revolutions of the driveshaft, the number of revolutions is equivilent to the gear ratio in the rear differential.... aka 3 and a half spins means you probably have 3.55's

[christianlarsen]

Im note sure on how to decode the VIN in relation to sure-grip diff. I found quit a bit of decoding site, but i can find any decoding instruction for sur-grip.

Can anyone tell me based on my vin-plate:

V1X        26 END
G33 H51 L31 M21 M31 R21
A01 A41 B51 C16 C55 G11
     Y2  C6X X9 320 198726
E61  D32 XP29 G9B 328790

[Ghoste]

Unfortunately, no.  You have a lot of information on there but that isn't among it.  Now if you have the broadcast sheet...

[Ghoste]

Did you jack the car up yet?  Also worth mentioning is that limited slips from the factory SHOULD have a tag on one of the rearend bolts that says "SURE GRIP".   Whether such a tag is there or not though is no guarantee after this much time.

[christianlarsen]

Hi again.

No i didnt jack the car yet. cause the engine is out pt and my jack is holding the transmission in place  im gonna try as soon as i get the enginge back in!

however i think i got the riddle solved...on the rearend is the number 2070741 and according to the web i have a 2070741 AKA "741" and this site (http://www.usaimports.co.uk/Mopar_Tech_Pages/mopar_rear_ends.htm) describes it as being a sure-grip diff and too weak for racing but ok for mild street applications and that in general its pretty hard to bust....i hope its gonna be ok for my 440->511 stroker 

thnx for advice Ghost! and if you (or any other) have comments/experience on the 741 i would sure like to hear about it...

[christianlarsen]

oh yeah...thanx also aifilaw!! 

[christianlarsen]

hmm im getting in doubt with regard to the existence of sure grip in the 741 or not.....it looks like it is optional according to some web info....can anybody confirm this ?

[aifilaw]

Since you don't know what your looking at, staring in a bolt hole won't help....get another jack and do it manually...it's the only way I think you will know for sure.

[CaptMarvel]

hmm im getting in doubt with regard to the existence of sure grip in the 741 or not.....it looks like it is optional according to some web info....can anybody confirm this ?

Yep, dont automatically assume. The 741 & 742 both came optional with it. I have a 68 factory R/T with a 440 and even it didnt have it originally. If that didnt, nothing is for sure...

[Ghoste]

The number you posted is just a casting number and the only useful info you can get from it is an approximate era of manufacture and the pinion shaft diameter.  Not that it isn't good to know, just that as perviously mentioned, it doesn't guarantee a Sure Grip.

[Paul G]

After you get the engine installed there is another way to tell if it is a sure grip or not. Do a burn out! If both tires lite up it is definitely a sure grip.

[aifilaw]

heh, it was only a matter of time before someone said it

But fact is my old engine produced about 500 ft lbs of torque.....and with my sure grip clutches broken (aka, spinning one tire with them off the ground made the other spin opposite( acted like an open differential)) it would spin both tires just because of the massive torque. So your test is bogus...although fun 

[Paul G]

 

[73chgrSE]

I jacked mine up and spun a tire, the other tire spins opposite. Is that sure grip or open? Whats the difference?

[mikepmcs]

you have an open rear.   you hit the mud or peel out and one tire spins.  Sure grip you would lay a nice dual patch on the road.  My Cousin Vinny (the movie) explains it pretty well.

v/r
mike

[73chgrSE]

Can it be converted to a sure grip? Would it be a good idea?

[mikepmcs]

Yes it can but you would be better off buying a center chunk off ebay or another vendor already done.  You do not want to tackle this on your own if you are not well versed in rear gear set-up.  lash adjustment etc......

You can get a decent set-up ready to bolt in for a decent price if you are patient.  They are getting good money for them these days but the deals are still out there.  Remove yours install the new/used one with new seals and you are all set.


v/r
Mike

[myk]

I just had mine converted a few days ago.  Other than the dual patches of rubber what other benefits will I enjoy from this new 'diff?

[73chgrSE]

I just had mine converted a few days ago.  Other than the dual patches of rubber what other benefits will I enjoy from this new 'diff?

What did that run, ballpark? If you care to share. I want to have it done too.

[myk]

I'll rebuild a hemi or restore a car before I try differentials or transmissions, lol, so I took it to a bunch of good 'ol guys at Pro-Gear in S.D. and I paid about $700 out the door.  They tell me there's no break-in for this thing so I'm tempted to see what this 'diff can do for me, but there HAS to be a break in period right?

$700 seems like alot, especially for the hardcore DIY'ers, but I just HAD to have a limited slip-the car doesn't seem to be "right" without one...