9 1/4 rear end with 3.23 limited slip and disc brakes from Imperial 1974-5

Here's one thing to consider when your going to install a cone, clutch, or gear type limited slip/posi. Some are going to have "drive shaft wind up" and others won't. Example: With both rear tires on the ground, trans in neutral, wheels blocked, and parking break set if you were to grab the drive shaft now and try to rotate it each way, it would be nearly impossible. The only slack you could feel or move would be the ring and pinion back lash, or any wear on the spider gears are cross pin... Now if you installed say a powertrax lok right, or a detroit tru trac you would be able to rotate the drive shaft a 1/2 or 3/4" each direction. That is the way they are designed as the gear or teeth bite into the case. The more torque put through the drive shaft makes the gears or teeth bite harder thus promoting lock up. I've installed numerous of these units in 9.25's , 9" fords, 10.50 sterlings, 8.5" gm's etc as I hate one wheel peels myself. If you go with a clutch type unit, it will be smooth, work great, no slop in the driveline. But the cons to a clutch type are : their not as strong as a gear type, some aren't rebuildable, and they cost alot more. I myself personally always go with a sure grip in the mopar 9.25 : because they set up so nicely , their a factory option so they are machined within a 1/2 a thousandth of an oe style open case, and their silent operation with no drive line slop. New bearings and races, swapping the ring gear onto the sure grip has always yielded the same gear tooth pattern and back lash readings as it was with the open carrier. I run the detroit tru tracs in my ford powerstrokes because they are manual trans so any drive line slop in hardly noticeable. Their tough, nearly unbreakable, aggressive , but not completely silent. I tried a powertrax lok right aka no slip system in a ford 9" and would never recommend one... They bite hard but their is always a racheting sound when turning and the drive line slop is horrible.... No surprise though as the install directions warned of this. I'm not sure what your cars daily use is but I personally would go for the sure grip, or one called an auburn gear which is clutch type. if you don't care about a bit of driveshaft wind up go for a tru trac. They have 3 gears on each side that bite into the case... Their not rebuildable, but ive yet to see one ever wear out. Stay way from the powertrax system which isn't a complete carrier replacement, it only replaces the side and spider gears.
 
Thank you. You summed up in one minute of reading years and years of questions I have been stockpiling in my head.
 
Thanks. Just trying to help a guy out so they didn't make the same mistakes I did over the years when I didn't know or understand the differences
 
Cones and clutches in Mopar world are 2 different carriers, the cones/ auburns are the only ones availble for 9.25. A clutch type with 2 crossshafts have friction clutches on the side gears, availible in the 8.75 and are rebuildable over and over, very strong and unpredictable on a slippery road acts a lot like a spool. Just thought i would cloud up you bright sunny enlightenment.;) I was under the asumtion the tru-trac was very quiet? No matter anyone who is bothered by noises in the rearend other than BOOM and old snow tire type grinding should just leave the peg leg in.
 
Issues I still need to work out:

1) If I keep 9 1/4 rear end is there an after market disc brake kit that will fit? If so what changes under the hood (which brake reservoir and ?)

2) If I keep the 9 1/4 vs rebuild my 8 3/4 489 case, and move the leaf spring from present 47.30 can I use same mounts and reweld? or new mounts?

3) Does the width of the 9 1/4 being 64 3/8 (about 1/2 wider each side) make a difference if I also have 7" rim and plan 245 or 255 R 6015 or maybe R70 15, do I have enough space under the wheel well.

4) Are the yokes the same for 8 3/4 and 9 1/4 to drive shaft

5) then I still need to decide if I go sure grip with gears, etc. as discussed above

THANK YOU - this is complicated stuff for me
 
THANK YOU - this is complicated stuff for me
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Anything can be done with enough money and head banging but I will throw in my 2¢ ad suggest you have enough on your plate and stick with the drums in the rear. The rear drums haul my NYB diwn just fine and parts are cheap over the counter.
 
How much power are planning, using slicks, racing? Either will handle good power and street tires of only 245-255, I am pretty sure that both came with small yokes and big yokes 2 1/8 or 2 5/8 across the yoke respectively I think the 9.25 has a longer axel center to yoke center dimension so driveshaft will need to be shortened. If it were me I would leave the 8 .75 in the car because they are the next best thing to a quick change when you get tired of droaning down the highway at 3500 rpm at 75 getting passed by fiat 500s. A 1/2 an hour and you can change it with some 2.76 and cruise at 80 and 2500rpm for hours. The 9.25 you are stuck with you first choice
 
best option

So is the best option to keep the drum and 8 3/4 even though I will have 500 hp? Any way to upgrade the front disc (slotted, different pads) that would increase the braking power with standard drums in rear

Is the true trac the strongest option with 8 3/4?

Thank you all for your help
 
With a 8.75 a 4 pinion clutch type is a really good unit, this is the one with 2 cross pins sitting in the Vs on the carrier, the tru trac has nothing to wear out and is gaining a great reputation. If you are only going to have 255 width tires you should not have a problem locking all 4 wheels. EIC has a drum to disc big brake conversion with 13" rrotors
 
I don't hear any noise out of my tru tracs unless I am towing a heavy load going up my steep concrete driveway.... steep as in its a 3:1 slope . It doesn't like it to much kinda bangs a bit but was deemed normal by eaton. I have heard other drag racers comment on the same noise under harsh abuse. One thing about a true trac is they need non synthetic petroleum based oil. I went with shell spirax 80w90. I tried synthetic and it didn't like it one bit..... Shell quieted it down tremendously. You may be able to find a power lok for an 8 3/4. If that was my car I would stay with the 8 3/4 because it can be set up on the work bench.. You'll need a special long reach tool for the spanner nuts on a 9.25... They are retained in the axle housing itself. I made one out of large nuts threaded and welded onto a piece of 1" all thread
 
They make chinese repop power locks I have no info and people are all over with opinions, I don't care about yours I am just mentioning it.
 
70bigblockdodge said:
They make chinese repop power locks I have no info and people are all over with opinions, I don't care about yours I am just mentioning it.
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I haven't seen the china made repop's lol... I would def stay away from them. Everything made in china is junk and wears out. Stick with high quality aftermarket rear end parts or OEM. I'm not even sure off the top of my head if auburn makes a 9.25 unit or a 8.75
 
Yeah they make one for both, the 4 pinion clutch type chinese one was really cheap like $250 but now up to $4something I don't know if I would go that high for one, might as well bite the bullet and $200 more get the Tru-trac.
 
if going with a tru trac and using the same ring and pinion : before disassembling anything .... Check your gear tooth pattern and back lash. Check the back lash in 4 spots. This is where I see a lot of people make a mistake because they only check 1 spot then complain of gear howl under de acceleration. Once you've swapped carriers put the backlash back exactly what is was before since this is s used ring a pinion. You won't have any gear howl. 8.75's are fairly simple to work on... Dana 60 fronts are the absolute worst . The side shins are behind the carrier bearings which have to be pressed off to make any back lash changes. Pita
 
Do you know if the 13" rotors and brakes would fit with the 15" inch 7" police interceptor rims
 
SuicideDoorLincoln said:
if going with a tru trac and using the same ring and pinion : before disassembling anything .... Check your gear tooth pattern and back lash. Check the back lash in 4 spots. This is where I see a lot of people make a mistake because they only check 1 spot then complain of gear howl under de acceleration. Once you've swapped carriers put the backlash back exactly what is was before since this is s used ring a pinion. You won't have any gear howl. 8.75's are fairly simple to work on... Dana 60 fronts are the absolute worst . The side shins are behind the carrier bearings which have to be pressed off to make any back lash changes. Pita
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Having worked in a truck shop - I agree 100%.
I'd got the 8 3/4 with a Tru Trac myself. Built about 8 of them over the years for customers- none have failed or are noisy.
 
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