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trashed another rear, what rear to use now? 489,742,741
Posted By: dirt
trashed another rear, what rear to use now? 489,742,741 - 04/13/09 11:14 PM
I tore up another rear. the pin that runs throught the posi unit came out and ran into the pinion gear and destroyed it. it was the type of posi without the clutch disc in it. this is the 3rd time this type of posi has came apart on me like this. all different cars but same type of posi. the clutch type has never came apart on me like this.
is this type of posi unit just not as strong? I have all of the 3 types of cases,741,742,and 489 and i want to build a unit to hold up to my driving. I also have a couple of the clutch style posi units that worked when i puled them out of the cars they were in.
I am running a dart with a edelbrock head 360,9.5-1 pistons,488 cam. in it with a 4 speed.the rear is quarter tubbed to fit n50 15 mickey thompsons on it.and i was wanting to run it on street nite at the strip.
what case would be best to use? also what one of the posi units is stronger? i will be running 4.30 gears.
also what brand of parts would you recomend?
thanks.
Posted By: Anonymous
Post deleted by Defbob - 04/13/09 11:15 PM
Posted By: Quicktree
Re: trashed another rear, what rear to use now? 489,742,741 - 04/13/09 11:17 PM
83/4s are bullet proof, what are you talking about? keep rebuilding them
Posted By: Triple Threat
Re: trashed another rear, what rear to use now? 489,742,741 - 04/13/09 11:17 PM
Seeing as you have torn up a couple 8 3/4 centers now, it might be time to look towards a dana. I know your combo isn't making tons of power, but the 4 speed is hard on parts.
If your going to stay with the 8 3/4 , either the 489 or 742 should be your next test ....
Posted By: actionange
Re: trashed another rear, what rear to use now? 489,742,741 - 04/13/09 11:46 PM
Quote:
83/4s are bullet proof, what are you talking about? keep rebuilding them
100% (LOL)!!!
Posted By: dirt
Re: trashed another rear, what rear to use now? 489,742,741 - 04/13/09 11:52 PM
a dana isint in the budget right now. its either fix the 8 3/4 or let it sit broken.
Posted By: Thumperdart
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 12:02 AM
I`ll sell you mine.
Joke; I use the 742 case and so far it`s holding up but, time will tell. I will eventually get the alum. center section and lighten the car but it`s what`s in it now so I run it. I agree 4-speeds kill stuff.
Posted By: hemi-itis
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 12:04 AM
Just put a spool in it
Posted By: VernMotor
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 12:15 AM
It's a cone pos..Junk! should never been in your car...buy a good one chutch type ..or a spool
Posted By: MR_P_BODY
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 12:23 AM
You keep breaking posi units, not the diff or gears.
The cone unit is sorta weak so use the clutch type
or go to a spool and the spool would be cheaper but
harder on the street(cornering)
Posted By: dirt
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 12:51 AM
i have a couple of the clutch type. i could rebuild them and use if they are stronger.I figured the cone type must be junk. i had the clutch type in my dart for 10 years and never tore it up. are they hard to rebuild? i always just used them the way they were
Posted By: Jimi_Vignogna
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 12:53 AM
Quote:
Just put a spool in it
that is like saying just put two dominators on a blown hemi 
Posted By: VernMotor
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 12:54 AM
I think I still have some new clutchs..if you was closer I show you to rebuild them..I ran one one the coronet for years..ran 8.00-7.70 in the 1/8 with one never hurt it.
Posted By: an8sec70cuda
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 01:38 AM
Get a spool, cheap and strong.
CHIP
Posted By: 446acuda
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 02:11 AM
Quote:
I also have a couple of the clutch style posi units that worked when i puled them out of the cars they were in.
like said above, avoid the cone junk. Between the clutch stuff that you already have you could probably come up with enough good clutches for one unit. If one of them has one piece side gears use those. Here is the clutch arrangement in the pic. All info is in the factory service manual but in a nutshell for swapping differentials, adjust gears to zero lash, tighten adjuster that is NOT on the ring gear side to achieve .006-.008" backlash (along with correct diff bearing preload)
Posted By: 446acuda
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 02:19 AM
Quote:
Get a spool, cheap and strong. CHIP
got to agree with that too. Each of those clutch sure grip are worth at least twice as much as one of those $100 ebay spools.
Posted By: CH3NO2
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 02:32 AM
you did,nt say what case you have, 489, ect. I suppose you have a 489 case, cone clutch, with a factory crush sleeve? That is the problem with them. Let us know all the info.
Posted By: dizuster
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 02:45 AM
Quote:
forget the 83/4 get a dana
Jeez', It's a 9.5:1 360 with a hydraulic cam for God's sake...and it didn't even break the ring gear or axle shaft, it broke a posi.
"Get a Dana" 
Posted By: Anonymous
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 02:50 AM
Quote:
I think I still have some new clutchs..if you was closer I show you to rebuild them..I ran one one the coronet for years..ran 8.00-7.70 in the 1/8 with one never hurt it.
your flying now, you go vern!!!
Posted By: Cab_Burge
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 02:54 AM
Quote:
a dana isint in the budget right now. its either fix the 8 3/4 or let it sit broken.
Let it sit until you can afford a GOOD Dana, small blocks with 4 speeds kill 8 3/4 eventually every time you race them, street or strip In fact any 4 speed Mopar that is raced on the street or strip will break the 8 3/4 eventually if it makes any power and hooks up at all 
Huh, Quicktree 
Posted By: dave571
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 03:49 AM
Quote:
Quote:
forget the 83/4 get a dana
Jeez', It's a 9.5:1 360 with a hydraulic cam for God's sake...and it didn't even break the ring gear or axle shaft, it broke a posi.
"Get a Dana"
How many more of them does he have to break before it won't seem so ridiculous 
I've seen similiar motors scatter 727's like they were made of fine china.
The combo is obviously hard on parts or this thread wouldn't be here.
As for the question, If you can't swing the dana now, go with the spool. It's cheap, and there's no pin to come out and smash your gears.
Most who say you can't drive a spool on the street, have never tried. My car is a spool(now in the dana, and was in the 8 3/4 too), and street driven. I doubt you would know the difference if you drove it
Posted By: dave571
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 03:51 AM
Quote:
Quote:
a dana isint in the budget right now. its either fix the 8 3/4 or let it sit broken.
Let it sit until you can afford a GOOD Dana, small blocks with 4 speeds kill 8 3/4 eventually every time you race them, street or strip In fact any 4 speed Mopar that is raced on the street or strip will break the 8 3/4 eventually if it makes any power and hooks up at all Huh, Quicktree
When I was reading this post, I thought it was Quicktree 
Posted By: Cab_Burge
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 05:29 AM
Quote:
Quote:
Quote:
a dana isint in the budget right now. its either fix the 8 3/4 or let it sit broken.
Let it sit until you can afford a GOOD Dana, small blocks with 4 speeds kill 8 3/4 eventually every time you race them, street or strip In fact any 4 speed Mopar that is raced on the street or strip will break the 8 3/4 eventually if it makes any power and hooks up at all Huh, Quicktree
When I was reading this post, I thought it was Quicktree
It ain't my favorite Ford Nine inch fan, it is me, the 8 3/4 lover. But not in 4 speed cars that hook 
Sorry to disappoint you or any other true Mopar lovers like me 
But I would rather be truthful and help a fellow Mopar racer save some bucks and frustration on trying to do something with a 8 3/4 to make it live behind a 4 speed when it won't live 
4 speed cars eat parts, you have to feed the monster, you can feed it tires or axles or U joints or ring and pinion or clutches and so on, but you got to feed it. I like feeding them tires and clutches, not U joints, axles or ring and pinion gears Been there, done that many years ago, Hemi Cuda 4 speed on nine inch tires 
on 8 3/4 in a 4 speed car
Posted By: dave571
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 05:57 AM
I'm with you here.
The proof is in the pudding. He's breaking them. Plain and simple.
Isn't the definition of insanity, to keep doing the same thing over and over, and expect a different result?
I understand budget restraints(that the original poster has mentioned), so thats why I suggested the spool. Hopefully that just doesn't make the breaking point move to the caps next.
Posted By: dirt
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 11:07 AM
I dont want to keep doing the same thing over thats why i started this thread. i thought the cone posi units may just be weaker than the disc type. the 3 i broke were 3 different cars over about 13 years.
I have smaller radial tires on it now also for the street, the sticky tires are not on it anymore unless i decide to race it and get better parts.
i tried a spool in another car and i didnt like it at all.the tires churped pulling out of parking lots, the got the cops attention ,the town cops like to have something to complain about.
I have a lot of center sections i could use ,489,742,741. what one is better?
I would like to get a dana for it but i would just like to get it driveable again until i can afford it. I figure i will keep the sticky tires off it until i get better parts.
Posted By: justinp61
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 12:22 PM
Rebuild the clutch type, install it in the 742 case and drive it. As mentioned above the cone style sure grips are junk.
Contact member Drdiff for the parts you need
.
Posted By: patrick
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 12:37 PM
the auburn (cone style) limited slip is a POS....some other (more expensive options) than rebuilding one of your existing clutch units would be the detroit tru-trac (torsen style limited slip) or a detroit locker.
Posted By: an8sec70cuda
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 12:56 PM
The 489 or 742 case are the ones to use. Both are strong. Pick one and get a new clutch style suregrip or spend the bucks on a locker for it if you don't want to use a spool. CHIP
Posted By: MR_P_BODY
Re: trashed another rear, what rear to use now? 489,742,741 - 04/14/09 01:05 PM
Quote:
The 489 or 742 case are the ones to use. Both are strong. Pick one and get a new clutch style suregrip or spend the bucks on a locker for it if you don't want to use a spool. CHIP
If you decide to go with the 489 case put in a solid
pinion spacer which is already in the 742 case, go with
either as long as you have the clutch posi for it
Posted By: JohnRR
Re: trashed another rear, what rear to use now? 489,742 - 04/14/09 02:01 PM
Quote:
I tore up another rear. the pin that runs throught the posi unit came out and ran into the pinion gear and destroyed it. it was the type of posi without the clutch disc in it. this is the 3rd time this type of posi has came apart on me like this. all different cars but same type of posi. the clutch type has never came apart on me like this.
is this type of posi unit just not as strong?
And yet you chose to keep using the cone type even after you killed the second one ... WHAT were you thinking ??
Cone types are GARBAGE and you should have realized that after the FIRST one failed ...
I've got a rebuilt one if you're feeling LUCKY ...
Posted By: JohnRR
Re: trashed another rear, what rear to use now? 489,742 - 04/14/09 02:06 PM
Quote:
Quote:
a dana isint in the budget right now. its either fix the 8 3/4 or let it sit broken.
Let it sit until you can afford a GOOD Dana, small blocks with 4 speeds kill 8 3/4 eventually every time you race them, street or strip In fact any 4 speed Mopar that is raced on the street or strip will break the 8 3/4 eventually if it makes any power and hooks up at all Huh, Quicktree
I have to agree with this, I killed a 3.23 single track behind a 340 with a 4 speed ... Chrysler released a TSB 1969 for 69 B bodies with an 8 3/4 and 3.91 gears in 4 speed cars , if they came in broken to replace the rear with a 4.10 Dana ...
Posted By: LAR_414
Re: trashed another rear, what rear to use now? 489,742 - 04/14/09 02:11 PM
I just scanned this thread, but here is my 2 pennys.
I'd go Dana with a power loc unit. A 4 speed will break 8 3/4 parts if it hooks up a bit. I would not go spool!
I just built a dana / power loc unit for my car and the clutches just broke in. WHen they were tight, it was like a spool. I don't care what others tell you, it is a PITA when the two axles are locked together on the street. If I'd turn the wheel about an inch, the car would come to a STOP. Backing out of my driveway required reving the freaking engine like the E-brake was fully engaged. Then the tires would chirp and the clutches would pop and bang. No lockers for me and no spools for me.
Heck Jim Pranis was going 8's in a 4000lbs charger with a Powerloc Dana!
Posted By: Blown61
Re: trashed another rear, what rear to use now? 489,742 - 04/14/09 02:53 PM
Aside from a crappy posi, what kills 8.75's the caps? I have not read about anyone breaking an axle just the caps.http://www.dragracingonline.com/xi_3-toc.html
http://www.risesales.com/pages/Dragracecentral/john_mccormack.htmllook at this car
Posted By: dirt
Re: trashed another rear, what rear to use now? 489,742 - 04/14/09 05:19 PM
To everyone who keeps asking me why i keep using the cone posi here is your answer. I didnt know what was in the rear until i broke it and tor the rear apart, it was 3 different cars.I didnt use that type again. but if the car i got came with it in it there was no way to know until i broke it and tore it down.
thanks for all of the advice.
Posted By: torkrules
Re: trashed another rear, what rear to use now? 489,742 - 04/14/09 05:20 PM
Quote:
Aside from a crappy posi, what kills 8.75's the caps? I have not read about anyone breaking an axle just the caps.http://www.dragracingonline.com/xi_3-toc.html
http://www.risesales.com/pages/Dragracecentral/john_mccormack.html
look at this car
I had an 8-3/4" 742 case in my 74 charger with a pretty hot 440 and an automatic. It was a clutch sure grip. The first time it broke, it broke the cross shafts right through the thrust plug holes. The pieces took out the ring gear. After I bought all new pieces and a higher strength cross shaft/pinion set, it lasted a few more years, but broke the same way. I've used a Dana ever since.
IMO I recommend in this order:
Dana 60 with Power Lok sure grip (clutch) or Detroit locker
8-3/4" with Power Lok sure grip (clutches)or Detroit Locker (if available) with aluminum MP center section
8-3/4" with spool and 742 or 489 case
8-3/4" with Power Lok sure grip (clutches)with 742 or 489 case and billet caps
8-3/4" with Power Lok sure grip (clutches) with 742 or 489 case
Even though you use the Power Lok, another weak area could be exposed (usually the left cap will break). It rally comes down to shock load (4 speed) weight and engine torque.
Posted By: Paul_Fancsali
Re: trashed another rear, what rear to use now? 489,742 - 04/14/09 08:49 PM
There is nothing wrong with a 8.75 they as strong or better then the so called super 9 inch Fords. My 4 spd car only broke one thing a side bearing went bad, and that was with 9 inch slicks and dropping the clutch 5 clutches to one bearing is not a bad ratio. When they are built right they work well by the way Dana's are not unbreakable, I have had several over the years blow out in truck applications and believe me it was nothing severe auto trans etc
Posted By: 446acuda
Re: trashed another rear, what rear to use now? 489,742 - 04/15/09 02:03 AM
Quote:
A 4 speed will break 8 3/4 parts if it hooks up a bit. I would not go spool!
And a solid hub dual disc clutch will break something between the clutch and the Dana. Put some slicks on it and you will find that something
Posted By: JohnRR
Re: trashed another rear, what rear to use now? 489,742 - 04/15/09 05:07 AM
Quote:
To everyone who keeps asking me why i keep using the cone posi here is your answer. I didnt know what was in the rear until i broke it and tor the rear apart, it was 3 different cars.I didnt use that type again. but if the car i got came with it in it there was no way to know until i broke it and tore it down.
thanks for all of the advice.
Sorry , you made it sound like you just kept putting cone types in everytime you broke one hoping third time was a charm ...
Posted By: Fury Fan
Re: trashed another rear, what rear to use now? 489,742,741 - 04/15/09 02:59 PM
Quote:
I tore up another rear. the pin that runs throught the posi unit came out and ran into the pinion gear and destroyed it. it was the type of posi without the clutch disc in it. this is the 3rd time this type of posi has came apart on me like this. all different cars but same type of posi. the clutch type has never came apart on me like this.
No, it was some people that replied that made it seem like he kept rebuilding them.
In typical webboard fashion, once you get more than a 1/2 page of replies your original question is distorted...
Posted By: LAR_414
Re: trashed another rear, what rear to use now? 489,742 - 04/15/09 03:11 PM
Quote:
Quote:
A 4 speed will break 8 3/4 parts if it hooks up a bit. I would not go spool!
And a solid hub dual disc clutch will break something between the clutch and the Dana. Put some slicks on it and you will find that something
You're probably right, but I plan on spinning the tires at the track. My dad's been doing it this way for 40 years. At my power level, I'll let the slicks turn a few revolutions and my parts should survive just fine!
Posted By: Moparmal
Re: trashed another rear, what rear to use now? 489,742,741 - 04/16/09 10:23 AM
Quote:
forget the 83/4 get a dana
Fred Im suprised you would say that - I remember you asking Ronnie Sox on my behalf a few years back what he ran....... and it was an 8.75 until he went to pro stock....
But maybe they swapped them out a lot more often? 
