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When should I look into a 12 bolt.

This is a discussion on When should I look into a 12 bolt. within the Drivetrain forums, part of the LSx Technical Help Section category; I am planning on getting the following soon: TSP 228R (228/228 .588/.588 114LSA) PRC Dual Spring, hardened push rods, Ti ...

  1. #1
    Senior Member Wheeler99WS6's Avatar
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    black, 05 Roush
    black, 99 T/A WS.6

    When should I look into a 12 bolt.

    I am planning on getting the following soon:

    TSP 228R (228/228 .588/.588 114LSA)
    PRC Dual Spring, hardened push rods, Ti ret.
    3200-3600 stall,
    LS6 ported oil pump, LS2 timing chain,
    LS6 intake, and of course a tune.

    These in addition to my current mods (in sig.) am I going to be in desperated need of a 12 bolt. If so I am thinking of only going with LS6 intake, the stall and tune. And just waiting on the rest if I am going to need a 12 bolt. I do plan on getting one eventually but not just yet. Would take a while to save up the cash for the 12 bolt. So if I need it to run the cam swap I want I will save up for the 12 bolt before buying the cam and support mods.
    1999 T/A WS6 Black -------SOLD
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    DOB manifold, m122 SC, 47lb injectors, gt500 TB, roush TVS CAI, Detroit rocker SC grind camshafts, Mac LTs, off road x, roush off road mufflers, roush short throw shifter, kenne bell BAP, Brenspeed 93 octane tune. 479rwhp 436ftlbs SAE.

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    Moderator Firebirdjones's Avatar
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    This question will get various answers. Your only saving grace right now is your auto trans.
    I personally would not start any heavy mods on a 3rd or 4th gen until a rearend swap is done. As a matter of fact, that would be one of the first things on my list if I planned alot of track time.
    I like these cars as much as the next guy but lets face it, GM cheaped out when it came to rearends on these things. They knew it, which is why they incorporated things like torque management in the tune, and a hydraulic clutch system that is sluggish (on 6 speed cars).
    I have seen quite of few nearly stock cars snap the factory 7.5 rear, axles mainly, even on street tires if the track is sticky enough.
    It's really up to you though. If you run rock hard street tires you can get away with it for a while. If you run drag radials on the street, it won't be long. If you spend alot of time at the track, make sure you bring the vehicle on a trailer.
    I guess it really depends on your driving habbits, your funds, and what you really want to do with the car. I would spring for the 12 bolt myself, get it done and not have to worry about it anymore.
    A 12 bolt is the first thing my buddy did with his 98 WS6 6-speed before it had 5,000 miles on it, everything else was still bone stock. Larry.

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    Just me Y2KPewterSS's Avatar
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    I have always been a firm believer in build from the back to the front. The stock 10 bolt is the weakest link of our drivetrain. The auto transmissions are a little more forgiving on the 10 bolt than the manual transmissions are. I have also witnessed a few of my friends stalled auto transmissions live on a 10 bolt for a few track seasons. But they eventually will go boom! You are always going to be on borrowed time with one and always have that doubt in your mind. When a stock 10 bolt goes, it often will damage an automatic tranny as well. I would be looking to upgrade your rearend ASAP if you take your car to the drags. If its just a street car, and you won't be launching hard on it, it will probably last you a while. Sorry for such a long post, but I tried to cover every scenario I can think of.
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    Moderator Firebirdjones's Avatar
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    Y2K is correct, I forgot to mention that, when the rearend goes, it sometimes takes other things with it. He mentioned tearing up the auto, a friend of mine lunched his 6 speed trans as well, when the rear let go it somehow shoved the driveshaft forward and busted the case of the 6 speed. Junked it. Very expensive lesson. Larry.

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    Just me Y2KPewterSS's Avatar
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    Quote Originally Posted by Firebirdjones View Post
    Y2K is correct, I forgot to mention that, when the rearend goes, it sometimes takes other things with it. He mentioned tearing up the auto, a friend of mine lunched his 6 speed trans as well, when the rear let go it somehow shoved the driveshaft forward and busted the case of the 6 speed. Junked it. Very expensive lesson. Larry.
    Same thing happened to my best friend this past year, cept he was an auto tranny. When the rear blew, it took his driveshaft, built tranny, and convertor all with it. Ended up costing him about $4,000 to have everything fixed and get the 12 bolt so he could roll again, very very costly.

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    Senior Member Wheeler99WS6's Avatar
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    black, 05 Roush
    black, 99 T/A WS.6

    I wont be going to the track a whole bunch, probably couple times to see what time I can pull. So if I was to get all these things I for sure would not want to try and launch it too many times correct (before 12 bolt installed)? I may just wait but then again I love the sound of a cam, I am sure I could keep myself from launching until I get a 12 bolt. Either way thanks for the input guys, I appreciate it.

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    JOSEY FUCKING WALES! Frankthetank's Avatar
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    LOl in the same boat u are......hehe i got a cammed out z......and ive put about 6000 miles on it and about 30 track passes (all on street tires though)
    I kinda waiting for it to go......YOu never know though........everyone has different experiences......I have a friend that was running over 500rwhp on a procharged ss and was running tens......IT took a while for his posi to start going out.........His rearend is still safe though,lol just a one tire burnoutwonder

    TSP Rumbler, LT's, TSP Tqr2, PRC 921 Springs, Comp Lifters, Chromoly 7.4" Pushrods, Titanium Retainers/Seats/Seals, ARP head bolts, BMR full Rear suspension

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    Bmike Dillard99's Avatar
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    hey guys tell me what you think about this web site
    its about beefing up the 10bolt rear end at www.thirdgen.org/beefinguprear
    do you think his set up will work.

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    Moderator Firebirdjones's Avatar
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    I have built a couple of 7.5's for people, and myself as well, with all good parts, meticulous setup and carefull attention to details, and they last for a good while. Still on borrowed time though if any racing is in order.
    I have a 7.5 in my monza, 406 sb with a muncie 4 speed, race the car regularly. Broken the rearend a couple of times. The last one I built was an Eaton pro series posi, 28 spline strange axles, new gears, setup kit etc....setting pinion depth and backlash pretty snug, again attention to details, bearing preloads etc....all new parts, and it lasted me about 3 years of abuse, a stick car with a stout 406,,,not too shabby, but the car only weighs 3,020 lbs. which is my saving grace. Cost me about $1,500 in parts to build, and after all that money you still only have a 7.5 10 bolt, ugh. Really didn't save any money. Just some of my experiences with them. Larry.

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    Bmike Dillard99's Avatar
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    thanks Larry for your info,
    I seen the site and I thought about trying that setup, was it difficult
    for you because I don't have $2,000-3,000 dollars to spend on a 12bolt at this time. It was said on the site that total cost was about $850,and what do
    you think about giving the axles a full weld when replacing them with a 28spline allow set as stated in the site and going with an heavy duty torsen diff set.

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    Senior Member Z28Thunder's Avatar
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    Quote Originally Posted by Y2KPewterSS View Post
    Same thing happened to my best friend this past year, cept he was an auto tranny. When the rear blew, it took his driveshaft, built tranny, and convertor all with it. Ended up costing him about $4,000 to have everything fixed and get the 12 bolt so he could roll again, very very costly.
    LoL only thing it took out was the 10 and the tranny Preston. I still have the same driveshaft on the car. I sent the convertor in to refresh it to make sure. TCI did not see any damage. But it is good to refresh stalls if your a track racer. The 10 bolt on the car lasted 6 years. Last 3 were racing. Years 4 and 5 it was a 3500 SSF and 2.73's. It could have ran forever like that. Added a cam to the setup and it still would have run forever with thoose gears. Sent the stall to TCI and had them make it a 4000 an put 3.73's out back. I went from 1.8 60' to 1.58 60'. The 10 ran a year with the 4000 and 3.73's cutting thoose 1.58 60'. The large stall and 3.73's put more strain on the drivetrain. IMO a 3500,cam and 2.73's could last a long time. Heck you could even hit it with nitrous. Just dont do it out of the whole and expect the rear to last. But since I dont run nitrous I can not speak from experince I could be wrong on that thought.

  12. #12
    Moderator Firebirdjones's Avatar
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    Hey Dillard, I went back and read that article to give it a fair shake.
    There are a couple things I don't like.
    I agree welding the axle tubes are ok. You are welding steel tubes to cast iron center section so it takes a little skill.
    I also agree, 28 axle splines are a must, preferably the aftermarket kind like I mentioned before, and I prefer a c-clip eliminator kit as well.
    The rear girdle cover is a good idea, it's main purpose is to preload the main caps. It's common for them to break in severe conditions, due to the pinion gear walking up the ring gear, and trying to constantly push the carrier against the main caps. The rear girdle cover protects against this and also extends ring and pinion life.

    The solid pinion bearing spacer I am not a big fan of though. I have set a couple rearends up with these (12 bolts) but same procedure applies here. My biggest gripe with them is not being able to properly setup the correct bearing preload and maintain that preload. I see no benefit to this spacer and cannot grasp how in any way it would help stabalize the pinion to keep it from walking up the ring gear (as mentioned in that article) The sole purpose of the crush sleeve is to apply proper bearing preload, thats all. The advantage to a solid spacer is supposed to be easier assembly and less setup time,,,,but I find that to be the opposite.
    I recommend sticking to the stock crush sleeve and setting bearing preload with an inch pound wrench, with new bearings you are looking for I believe 25-30 inch lbs. of drag, (this is your preload).
    Lastly,,,,the zexel torsen diff I don't like either. I have found these things create a boat load of metal shavings, even with just regular driving. It's all gear to gear inside, and just creates shrapnel everywhere, which is not good for bearings. If you run one of these I recommend gear oil changes at least every 10,000 miles if not sooner. Even SLP lists this in there owners manual suppliment when running this posi,,,they say, make the first oil change at 6,500 miles and then every 15,000 miles after that,,,,this is a testiment to the fact that these things make shrapnel, and you don't want it floating around in there very long. I would change the oil sooner myself, at least every 10,000 like I said. Or take my advice and stay away from this hunk of a door stop all together.
    I prefer the clutch style posi's, especially if you have any street driving in mind between track sessions. Eaton is the way to go when it comes to these, stay away from the Auburn's, they are cheaper but there is a reason for that. They use cones rather than clutches, and are not rebuildable, once they are worn, their done.
    Eaton's use clutches, they are the manufacture of all the original posi's used in the muscle cars throughout the 60's and 70's, proven themselves over time. They are rebuildable which is another plus. With the various styles of clutch pack materials available, and different spring packs to adjust preload on the clutches,,,slippage is not an issue anymore, and they last for 10's of thousands of miles. When I rebuild them I set them up pretty tight with stouter springs and better friction material,,,they don't slip and work great. Whats great is you can rebuild these and tailor them to an individuals personal preferance.
    I have used the Eaton pro series which is pretty good right out of the box, with heat treated spyder gears etc...it will chatter and chirp the tires on a sharp turn with a little throttle applied, works like a champ.
    Another one of my favorites is the Moroso Brute Strength posi that I run in my chevelle. These are only available for 12 bolts that I am aware of, but it's a clutch style posi and basically a copy of the Eaton series unit.
    The Moroso unit is setup pretty tight and works awsome. I have had this unit in my 454 chevelle since 1988 with more drag strip passes than I can count over the last 20 years or so, and I put about 5-8,000 street miles a year on this car as well. Still works perfectly, haven't had to touch a thing on it,,,cut's 1.5 60 foot times and runs low 11's.
    Sorry, enough babbling now.
    If you have the funds a 12 bolt is the way to go, but if you want to experiment with the 10 bolt, thats fine, it's a good way to get your feet wet experimenting with things and see what works, what breaks, etc....just try not to sink too much money in it,,,after a while you might regret not getting that 12 bolt. Hope that helps,,,Larry.

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    Bmike Dillard99's Avatar
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    hey larry thanks alot, very good info don't mine the the long info I love to learn I appreciate your time and will take it in. I would may be go with the
    eaton posi like I was at first thanks alot.

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