Mainly spinning 1 tire...

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iThe 8 3/4 is a "quick change" setup. Kind of like a Ford 9 inch. You can tell cause there are no cover bolts on the rear "Pumpkin. You basically pull the drums, remove some bolts for the axles, slide them clear of the differential, remove the u joint straps, remove the differential bolts , pull the chunk, then slap another one in. It worked really good for the guy who drove a street gear, then swapped it out to go to the track. For ease, I would recommend you obtain a Sure Grip, a gasket, and put it in. But keep in mind if it is a used unit, someone may have played around with it. You can set up pinion depth and backlash on the bench before you install it.
 
It looks most like 2681489. What is for sure is the 2--1489. I'm not sure if it is 266, 268, or 288. Not enough light. Got home late, left out early.

Is the 489 OK?


7milesout
 
And I'll add, if it is between a $300 SG, and a $500 Truetrac, I'll spend $500 because it sounds like the SG is good, but the Truetrac is more than $200 better. What little I've read so far, it sounds like the Truetrac is mechanically superior and is a true maintenance free diff. And as inexperienced as I am, I am a perfectionist. So when it comes to whether I do this diff, or I let someone else do it ... I will do it. It may take me a couple months to do the install once I get it. But it will be right. I've heard a few stories of having a brand new diff get put in and it going bad in short order. So I trust no one.
 
7milesout said:
Even if the wheels spin different directions, can I still spin the wheel one rev and count the turns of the driveshaft to determine the ratio?

7milesout
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That will work with a sure-grip only. With an "open" diff there is a 2:1 ratio. If you want an accurate ratio estimate for either type of diff you need way more than one tire revolution. Here is a good example: Mark a reference line on both the driveshaft and on the tire. With a sure-grip, rotate the tire exactly 4 revolutions. Have a helper count the revolutions of the driveshaft. Let's say the shaft rotated "about 14" times. Dividing 14 by 4 we get 3.50, so its probably a 3.55 gear. The more revs you make, the more accurate the final number.
The same scenario for an "open" diff would be: Rotate the tire exactly 8 times, while your helper counts the driveshaft revs. Same as above, the shaft rotated around 14 times. To figure gear ratio divide 14 by 8, and then multiply by 2. Same answer, somewhere around 3.50.
 
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To follow up on this thread, I chose to outsource the job. I did buy the Truetrac and the install was completed today. I'm going to pick it up tomorrow. The car has a 3.23 gear in it.
 
I think he got it backwards, only time you should have to turn the front wheels is when the rear are already spinning.

:lol:
 
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The cone-type SG has 2 planetaries and 1 crosspin to share the load
The TracLoc has 4 planetaries and 2 crosspins
I like the trac-Locs for the street
Either will work on the street with under 450hp, flip a coin.
You can even get a mini ratchet to install in the open case unit. Fast, Easy, and cheap.
 
71DodgeDemon340 said:
If you decide to go with a clutch type make sure you add 2-3 bottles of mopar friction additive
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Do you think that might be a lil much? I don't know what the consequences might be of running too much. I guess it kindof depends on the size of the bottles, but I only run one or less.
 
I have heard that one bottle isnt enough, i know mine chattered lightly going around a slight uphill curb until i put another bottle in it. Felt like it was trying to lock and unlock. Still does it every once in a while but its only uphill with a slight curve and lower speeds higher rpm, like 10-15 in 1st at 2-3k rpm it will do it. Going down the road at 30mph its fine around curves. I also had a old timer tell me one time at a car show that the mopars with the clutch type differentials seemed to like more additive but from experience it seems to help
 
I set my cone-types up with 120Ftlbs turning torque with the correct (listed on the bottle) percentage of additive,pre-installed, and so have never had a problem. Too much more than 130 tho, it skids the inside tire. Less than 80 it will occasionally pegleg. The sweetspot seems to be 100 to 120. This for BFG 295/50-15s......Your results may vary,lol.
 
Maybe thats part of my issue not sure, i had a mopar trans and driveline guy set up the third member for me. Im running 275/60r15’s. I might have it do it once every 10 times i drive in that certain place. Not sure if its just a characteristic of the diff paired with the 4 speed or what, nothing is broken yet so i guess thats a good thing lol. Im with ya aj, i put one 8oz bottle in it to start and i put another 8oz bottle in it and seemed to help a bunch
 
That stuff is very slippery.I could imagine that if someone set the diff up tighter than I do, then a little extra whale-oil would bring it back into range.

That's one of the reasons I prefer the trac-locs; they have a wider range of usability.
 
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