beef up a 7.5 rear

Old May 8th, 2018, 04:32 AM
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beef up a 7.5 rear

is it possible to build the exsisting rear in my 80 cutlass to hold up to the 455 im building?will be over 500 ft.lbs of torque.ive looked at an auburn carrier and moser axles that are priced in my budget but not sure hold it would all hold up.i would rather not change out the entire rear if i dont have to .this will be mostly a street driven weekend tire fryer with 3:23 gears. thanks for any input
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Old May 8th, 2018, 05:56 AM
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beefed up 7.5

On the steet it will be fine as long as you use aftermarket posi unit as and axles and most importantly SET IT UP CORRECT. The set-up is what really makes parts last long and give them the strength.

The best 7.5 set-up i have seen is the 28 spline moser unit with a true trac unit and any aftermarket gears.

dura grip and eaton and auburn will still all be a major improvement over the stock carriers. ALL 28 spline.

IF you are going to the track and you hit that rear too hard the spiders will blow sky high after about 5-10 hits... IF you do round de round racing...meaning you hot lap at the drag race track. Heat up and cool down make life a lot easier on parts.

Remember too NEW ring and pinion (and really all metal parts new castings) like a break in period for hardening to happen ...The heat up and complete cool down is what rockwell the ring and pinion and it sure does not hurt the rest of the steel parts in the rear.

Good luck, Jim
J D Race
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Old May 8th, 2018, 06:10 AM
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Jim thank you for your advice, I do have a guy that’s built many rear ends so he will help me set it up properly .
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Old May 8th, 2018, 05:20 PM
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all rears

Ok, Like i said that is one of the biggest keys to getting anything to last

Motors trans and rears,.

Jim
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Old May 9th, 2018, 05:10 AM
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Agree on the Trutrac, it eliminates the tiny spider gears. Look at 4th Gen Camaro/Firebird, many had 3.23 or 3.42 gears with the Zexel Torsen(Trutrac) worm gear posi, usually used combos on eBay, just add Moser 28 spline G body axles. The stock 26 spline spider gears are soft, I exploded a set with my 403. I used the Yukon spider gears, help up fine with slicks, unlike stock spider gears or the Powertrax No Slip.
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Old May 9th, 2018, 06:01 AM
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I had a 12:90 G-body 403 with 4:10 posi, never a problem. I had drag radials. Always be straight when heating the tires and never do a turning burn out like the idiots on tv. Jmo
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Old June 8th, 2018, 12:01 PM
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Old October 13th, 2018, 06:39 PM
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Originally Posted by monzaz View Post
On the steet it will be fine as long as you use aftermarket posi unit as and axles and most importantly SET IT UP CORRECT. The set-up is what really makes parts last long and give them the strength.

The best 7.5 set-up i have seen is the 28 spline moser unit with a true trac unit and any aftermarket gears.

dura grip and eaton and auburn will still all be a major improvement over the stock carriers. ALL 28 spline.

IF you are going to the track and you hit that rear too hard the spiders will blow sky high after about 5-10 hits... IF you do round de round racing...meaning you hot lap at the drag race track. Heat up and cool down make life a lot easier on parts.

Remember too NEW ring and pinion (and really all metal parts new castings) like a break in period for hardening to happen ...The heat up and complete cool down is what rockwell the ring and pinion and it sure does not hurt the rest of the steel parts in the rear.

Good luck, Jim
J D Race
Here is your Rockwell hardening lesson people.Also I didn't realize that anyone could predict how many hits you can put a rearend through before it comes apart,I guess the great Monzaz is psychic also.I will not use an Auburn posi in anything,Any unit that sends metal through your new rearend all while it's in there in my opinion is junk.Might as well give your customer a bottle of metal fragments to use for additive.An Auburn is a design that has occurred after the patent limitations ran out on the old Borg Warner unit.Chevrolet had service bullitins out to all the dealers that if a failed cone type Borg Warner unit is removed,do not replace it with another,use an Eaton.There are no clutches in an Auburn,it is a male cone being jammed into the female portion of the diff case resulting in metal to metal contact to lock up .They are not rebuildeable,you throw them out
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Old October 13th, 2018, 08:06 PM
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Give up

Now your saying that there is no metal wearing in a Eaton clutch. (picture provided of eaton STEEL clutches) Why do you keep this up. ALL bearings spider gears metal to metal parts will WEAR... or nothing would every WEAR OUT... silly. This is why we change the oil to clean out wear debris and get fresh oil in to help slow down the wear process and lubricate. What about pistons and crankshaft babbitt metal that they ride on wears too.... so you will never use another piston or camshaft or anything that metal rubs against.

It is so easy to refute and knock other people down. You are just making your self look silly and childish


This will be the last time will give you response on any thread you post. I do not think we all have as much time as you to stalk people.
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Old October 13th, 2018, 08:46 PM
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Originally Posted by SmirchIs#1 View Post
.They are not rebuildeable,you throw them out
I disagree with this. Back in the late 1980s my brother-in-law had the cone posi in his '68 GTO machined to bring it back to functionality. Several years ago I saw an online article detailing the machining process to bring them back to spec.

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Old October 21st, 2018, 04:59 PM
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Originally Posted by monzaz View Post
Now your saying that there is no metal wearing in a Eaton clutch. (picture provided of eaton STEEL clutches) Why do you keep this up. ALL bearings spider gears metal to metal parts will WEAR... or nothing would every WEAR OUT... silly. This is why we change the oil to clean out wear debris and get fresh oil in to help slow down the wear process and lubricate. What about pistons and crankshaft babbitt metal that they ride on wears too.... so you will never use another piston or camshaft or anything that metal rubs against.

It is so easy to refute and knock other people down. You are just making your self look silly and childish


This will be the last time will give you response on any thread you post. I do not think we all have as much time as you to stalk people.
I have rebuilt and blueprinted many HIGH mileage Eaton clutch type posi units and used the original clutches which would not be possible if they wore at the rate of a cone type unit.Yes I have seen units where the clutches were bad or overheated.This condition is usually caused by someone running two diff. size tires on the rear causing the clutches to spin rapidly even going down a straight road.In this situation the clutches over heat and warp and or gall.On the other hand the Borg Warner cone type posi with less than fifty thousand miles,you might find one out of twenty that is not spent.That is why Chevrolet sent service bullitins out to their dealers to not replace a spent cone type unit with another.As far as your comment about me stalking,YOU are the one that told everyone on this website that my posi was junk and said the you don't think I know rears.Your arrogant self started this,now deal with it.
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Old October 21st, 2018, 05:25 PM
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Originally Posted by Fun71 View Post
I disagree with this. Back in the late 1980s my brother-in-law had the cone posi in his '68 GTO machined to bring it back to functionality. Several years ago I saw an online article detailing the machining process to bring them back to spec.
To you sir,You are absolutely correct.It doesn't even take a machinist to do this.It can be done with some simple grinding tools and mechanical aptitude.I am guilty of performing this for customers when I was much younger.Back then there were no options.Auburn was the first to fill this void(still junk),and then finally Eaton made a quality unit.Please understand this,The internal machined stop was built into these units for a reason.As the male portion of the cone wears deeper into the female portion(diff. case half),the side gear or drive gear moves away from the little spider gears,thus the amount of tooth contact between the two becomes minimized.If you modify the unit by grinding the internal stops,You are allowing the tooth contact to become marginalized.With any apprecial power the spiders will grenade.Now even worse cenario is if you modify a Chevy or "C" clip unit,you have created a dangerous situation.As it wears further you will have enough end play in the axles to loose a "C" clip and the you loose an AXLE on a corner,would't that be fun
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