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Converting to Posi

the trutrac tries to sent equal power to both tires not try to make them go the same speed as does a clutch type or selectable locker or spool
and some thing like a Detroit locker drives the slowest tire and fastest ratchets ahead that is why they click and tires squeal when turning and accelerating
 
You are in guelph you should have gone to mopar fest there was plenty of connections there to help you out.there is a guy north east of orangeville who has a good knowledge on mopar and has a lot and trailers of good used mopar parts. Check out your local trans shops and find somebody who is familer up where i am tripple t transmission has an older gent working for him and is quite knowledgable on muscle car diffs of all makes.
 
Here's my cost:
$200 ring and pinion
$125 install kit w bearings
$30 crush sleeve eliminator (for 489 only - optional but not necessary)
$200 +/- for set up and machining of cone.
-------
$550 approx cost (I already have the sure grip) plus I'll recoup like $50 for the old ring and pinion so like $500. Just make sure that install kit has new bearings, and for $43 I'm guessing not?
 
CHARGERSTEVEN said:
You are in guelph you should have gone to mopar fest there was plenty of connections there to help you out.there is a guy north east of orangeville who has a good knowledge on mopar and has a lot and trailers of good used mopar parts. Check out your local trans shops and find somebody who is familer up where i am tripple t transmission has an older gent working for him and is quite knowledgable on muscle car diffs of all makes.
Click to expand...

I skipped Moparfest this year and just went to the Saturday night burnout contest and show & shine here in town.... North East of Orangeville... Is this that Moparts spot? I was planning on asking around and hears some talk of a place around here that does truck diff's that might have something for me...

HT413 said:
Here's my cost:
$200 ring and pinion
$125 install kit w bearings
$30 crush sleeve eliminator (for 489 only - optional but not necessary)
$200 +/- for set up and machining of cone.
-------
$550 approx cost (I already have the sure grip) plus I'll recoup like $50 for the old ring and pinion so like $500. Just make sure that install kit has new bearings, and for $43 I'm guessing not?
Click to expand...


No it didn't include bearings I forgot in my total I had $65 in there for bearings... so if you actually add up my math it should be wrong by $65 :(...
 
I bought a 3.91 posi unit 3rd member for my 8 3/4 rear end in my RR, for 450.00. Installed it myself and haven't had a problem. Then I saw a 3.91 posi in Omaha for $175 plus shipping, which was another $80. Put it in my sons Super Bee, and it works great too! Had to set the backlash on both units to .008" is all. Easy to do. This is the best way to go for me. Buy a 3rd member, in the gear ratio you want, and put it in. Takes about 2 hours if you go slow.
 
I went with a Tru-trac and 3.73 gears. My buddies friend is a Mopar mechanic for 30 years and drag races a 80's style Charger he built from the ground up. It's NHRA sanctioned and does a 8.50 in the quarter. He built it up the rear end and rebuilt my tranny. I'm very confident in his abilities when he tells me it will withstand anything I throw at it. Don't have it in the car yet because it's being painted but soon. Only heard of good things about a True-Trac for street driving.
 
HYRDGOON said:
Now I feel like I'm getting somewhere :)

So just what I gather as an idea of cost wise from Dr. Diff site... Housing Gasket & Seal $25, Installation Kit $43, Ring & Pinion $185-200, and 8 3/4 clutch type sure-grip $375.... comes to about $730 plus taxes etc...

So vs. a new complete centre section for $1300 this seems more feasible... Unless the installation of the components vs. installing a new centre section would take more than 12 Hours @ $50/hr


Thanks everyone for your replies I actually have a better idea now of the breakdown of components and what goes with what


OOPS! I didn't compare dollars to doughnuts! add $200 to $730 to compare and Eaton True Trac to a complete centre section... so difference of $400
Click to expand...

Don't forget to ad the cost of the case itself, + the heavy duty pinion yoke, and then the labor to get it all together. Now I know how i got to $1,300!. And Cass (Dr. Diff) threw in the green bearings with the unit when I got it at Spring Fling...

Oh. BTW - You asked if it was noisy on the street - Not that I can tell over the exhaust! Actually I haven't heard it make a sound other than screeching tires...
 
Grabinov911 said:
Don't forget to ad the cost of the case itself, + the heavy duty pinion yoke, and then the labor to get it all together. Now I know how i got to $1,300!. And Cass (Dr. Diff) threw in the green bearings with the unit when I got it at Spring Fling...

Oh. BTW - You asked if it was noisy on the street - Not that I can tell over the exhaust! Actually I haven't heard it make a sound other than screeching tires...
Click to expand...

Hey Grabinov,

I hadn't forgotten I was just taking a tally of these I need to replace vs. the cost of replacing the complete centre so I knew how much I could get away with... that said and this SHOULD be my last question...
If I were to order essentially the exact same unit as you (i.e. when you order the whole centre) Do I have to specify what I have now (741 742 489) or is the new centre a direct swap for 8 3/4 despite what is existing?
 
I am like you starting with zero knowledge of rear diffs. My 1969 Coronet R/T had a 741 open case with 2.76 gears. I bought a 489 TruTrac 3.55 and new axles with new style green bearings from Cass (Doctor Diff). I highly recommend buying a complete third member from him. The installation was simple; just remove the old and replace with new.

A FBBO member a few months ago bought the parts (TruTrac, 3.73) and had them installed. The gears made noise which his shop told him would get quieter with wear. Some warranty. Buy from Cass and get a warranty you can live with; not noise or other problems.

FYI, Cass (Doctor Diff) told me he will be at SEMA all next week. Call or email and he will get back to you.
 
Thanks TM! so did you have to change the axles because you went from a 741 to a 489 or is that something you just opted to do? I am leaning towards the complete centre unit with a TruTrac 3:55 as well from what I have learned in this thread but am just feeling out now EXACTLY what will be required.

I'll be "visiting" my car on Wednesay so I'll get a look at the casing then and see what I have
 
Axles interchange between all 3 and all 3 will bolt up to any 8-3/4 rear housing. Only issue you might have is if you go with some other brand limited slip unit (like Detroit locker, a spool, etc) as the spline count could possibly be different than the oem axles if you're not careful when you order.
 
Thanks HT413 that's pretty much all my questions answered... Now I'll have to start a thread just like this about Clutches so I can understand more about picking a replacement there! lol
 
Ever give the Richmond Powertrax a thought for converting your 'peg leg' to a locker? I'm using one, it's been great the past few thousand miles. Pretty cheap too, considering the price of posi's and Detroit lockers.
 
Sweet5ltr said:
Ever give the Richmond Powertrax a thought for converting your 'peg leg' to a locker? I'm using one, it's been great the past few thousand miles. Pretty cheap too, considering the price of posi's and Detroit lockers.
Click to expand...

I haven't but I'll check it out... I've really only looked at Dr. Diff and Randy's for prices but as you can tell I'm starting from scratch on there where's and what's

- - - Updated - - -

Ok I just looked at Richmond's site but can't really get any info on what the Powertrax is or how it's different? Is it a completely different type of application? What vendor would you use?
 
If all you want is a locker and no gear change the lunch box locker is something to look at but would recommend if you are paying to set new gears up you go with a full case locker or lsd the other one just replaces the spider and side gears
 
HYRDGOON said:
I haven't but I'll check it out... I've really only looked at Dr. Diff and Randy's for prices but as you can tell I'm starting from scratch on there where's and what's

- - - Updated - - -

Ok I just looked at Richmond's site but can't really get any info on what the Powertrax is or how it's different? Is it a completely different type of application? What vendor would you use?
Click to expand...

http://m.summitracing.com/parts/PWT-1240-LR/

It just replaces your spider gears. Easy install. Dr. Diff axles are great though.
 
I have a posi unit here with no gears i will be stopping in camebridge on friday if you want to have a look at it
 
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