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#1
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Anyone With The Moser 12 Bolt, A Body Rear End? Thoughts
Time to address this last aspect of the car now that the engine is done and making 600tq.
I'll be selling my 8.2 "N" rear end with disk brakes and I'm really leaning towards the .. Moser 12 bolt for A bodies 30 spline Eaton posi 3.91 gears (30" Street R tire probably next) 11" rotor with Dynapro 4 piston PC black gloss They said the brakes have e brake function and lines. The rear length is factory so wheels will be in the same spot. All suspension points will line up Driveshaft will bolt on without issue (3" steel) Curious what you all that have one can comment on? Thanks
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69 GTO Convertible, 4000lbs 462ci, 606tq/569hp - 93 oct @ 34 deg (207psi) 11.7:1, KRE H Ports, Lunati HR 282/290 w Johnson Lifters & 1.65 Scorp, E30, EFI, Holley HP + Dual Sync, 12-1 Crank Trig, 120lb Inj & 1000cfm TB, Torker II EFI Int & Rails, PTC 10", Ricks SS Gas Tank, Magna 4303, Aerom EFI Reg, Aero Front & Wilwood Rear Disc Brakes, Dougs 1 7/8" & Borla Pro XS 3", Alum Rad & Dual Fans, 12:1 Box, UMI Arms & Viking Berz Fr + Rear CO Shocks, Hella UP28 Vac Pump, 12 Bolt, 3.73, 33 Spline |
The Following User Says Thank You to GOAT8U2 For This Useful Post: | ||
#2
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Absolutely wonderful piece of equipment. Now that sucker wasn’t cheap though.
Wilwood discs. 3.42 No issues. Won’t need the hop stop bars for the top. The casting is already modified 1.5” taller there to begin with. Stout piece. |
#3
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I have a Moser 12 in my 69 bird. It's a great piece. It was setup well from Moser. I haven't had a single issue with it.
I opted for the TruTrac instead of a traditional posi unit. I still like the trutrac better, especially for bigger power on the street. The dynopro wilwood kit will have a drum in hat parking brake. You'll need to get their universal parking brake cable and adapt it into the factory cable.
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-Jason 1969 Pontiac Firebird |
#4
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I did the same in my 67 but went with the bigger 1350 yoke and 33 spline axles
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67 Firebird Convertible |
#5
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I just picked mine up yesterday for my 68 FB from Spohn's Performance. Took 10 days from the time I ordered it. I also got the 1350 yoke, 33 spline axles, True-Trak, 3.91 gears, powder coating and aluminum girdle cover. I'm using my stock drum brakes. Cost was a little over $3600 before tax and shipping. My car is equipped with a 2004R trans.
Last edited by JLBIII; 02-15-2024 at 10:54 PM. |
#6
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Thanks guys...
With the 1.5" taller, I didn't have hop stop bars at $315 but I suspect my adjustable upper arms will just need to be tweaked to fit in this new raised position? Trutrac (worm gear?) was only a $30 upgrade vs normal Eaton posi, it's with the upgrade?
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69 GTO Convertible, 4000lbs 462ci, 606tq/569hp - 93 oct @ 34 deg (207psi) 11.7:1, KRE H Ports, Lunati HR 282/290 w Johnson Lifters & 1.65 Scorp, E30, EFI, Holley HP + Dual Sync, 12-1 Crank Trig, 120lb Inj & 1000cfm TB, Torker II EFI Int & Rails, PTC 10", Ricks SS Gas Tank, Magna 4303, Aerom EFI Reg, Aero Front & Wilwood Rear Disc Brakes, Dougs 1 7/8" & Borla Pro XS 3", Alum Rad & Dual Fans, 12:1 Box, UMI Arms & Viking Berz Fr + Rear CO Shocks, Hella UP28 Vac Pump, 12 Bolt, 3.73, 33 Spline |
#7
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The TruTrac has no clutches to wear and differs in that it is torque splitting towards the loaded gear. It can sent around 70-75% of the available power to the tire with the most traction, while still allowing the wheels to rotate at varying speeds. On a dragstrip launch this means you'll typically torque split nearly evenly and the car should launch straight. Powering out of a corner the outer wheel which has the traction will be receiving the brunt of the power. This is unlike powering out of a corner with a posi where the application of torque will begin to lock the two wheels together in rotation speed. Anywhere you would use a Posi over something like a spool, the helical gear differential almost always works better, is stronger and has less maintenance. Plus no need for any friction modifiers. Just run straight 90 weight conventional gear oil.
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-Jason 1969 Pontiac Firebird |
The Following User Says Thank You to JLMounce For This Useful Post: | ||
#8
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When I put Stop Hop bars on my stock rear end I was able to use the same stock upper CAs. You should be fine with yours.
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1967 Firechicken, 499", Edl heads, 262/266@0.050" duration and 0.627"/0.643 lift SR cam, 3.90 gear, 28" tire, 3550#. 10.01@134.3 mph with a 1.45 60'. Still WAY under the rollbar rule. |
#9
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Thanks that solved that ?
The parking brake, since I'm auto its value decreases and mainly for emergency brake. Is this drum in hat thing worth it all, I'm leaning yes since I've needed the E brake 1x in my life and glad I had it.
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69 GTO Convertible, 4000lbs 462ci, 606tq/569hp - 93 oct @ 34 deg (207psi) 11.7:1, KRE H Ports, Lunati HR 282/290 w Johnson Lifters & 1.65 Scorp, E30, EFI, Holley HP + Dual Sync, 12-1 Crank Trig, 120lb Inj & 1000cfm TB, Torker II EFI Int & Rails, PTC 10", Ricks SS Gas Tank, Magna 4303, Aerom EFI Reg, Aero Front & Wilwood Rear Disc Brakes, Dougs 1 7/8" & Borla Pro XS 3", Alum Rad & Dual Fans, 12:1 Box, UMI Arms & Viking Berz Fr + Rear CO Shocks, Hella UP28 Vac Pump, 12 Bolt, 3.73, 33 Spline |
#10
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I think Strange is base out of the Chicago area. Might be worth giving them a call if it is in your area. They have 9” options also.
The cheapest and strongest aftermarket option in a A body is actually a Strange Dana 60. |
#11
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That is what Strange claims. Lol
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#12
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Do you know the difference in price between the 12 bolt and a 9"? I bought the Ford only because I wanted to be able to change ratios quickly. Having spare center sections I can change ratios in a half hour. I also use the soft locker. Do you really need the rear disc brakes? Rear brakes really don't make a big difference.
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#13
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#14
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I have a Moser 9" rear under my 64 GTO.
Very happy with the quality of the unit. Only thing I did was, years later, was shorten the rear end width so I could mount Ford Explorer rear disc brakes. Those Moser rear axles are some hard to machine parts. Very happy with their products. I run a steel Strange 9 inch 3rd member. I was told that some of the Moser rears, 8.5" are very strong. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#15
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I have a Moser 9" rear under my 64 GTO.
Very happy with the quality of the unit. Only thing I did was, years later, was shorten the rear end width so I could mount Ford Explorer rear disc brakes. Those Moser rear axles are some hard to machine parts. Very happy with their products. I run a steel Strange 9 inch 3rd member. 33 spline axles. I was told that some of the Moser rears, 8.5" are very strong. No info on the 12 bolt stuff. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#16
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I didn’t know Moser made an 8.5
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Will Rivera '69 Firebird 400/461, 290+ E D-Ports, HR 230/236, 4l80E, 8.5 Rear, 3.55 gears ‘66 Lemans, 455, KRE D-Ports, TH350, 12 bolt 3.90 gears '69 LeMans Vert, 350, #47 heads: work in progress |
#17
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Have a Moser 12 bolt Muscle Pak with the economy disc brakes with parking brake, Eaton posi 3.73. I had them make it 4 inches narrower so I could tuck my N50-15s underneath. Powder coated black, fit perfect. 70 Judge
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#18
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First one was a 3.55 True-Trac, but without brakes, 2nd one was a 3.90 Wave-trac. A bit of overkill, but nice peace of mind. IIRC, I had an 11X2 rear drum brake set-up on both. Both had pinion seal leaks.....ugh!!, |
#19
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I've got no iron in this fire so to speak happy with my 8.5" 10 bolt from a skylark, but looking at the Moser sight with a few little upgrades and unpainted this 12 bolt still comes in at $5000 you can but TWO very similarly built 9" rears from quick performance for this price point. I know some are purists and nothing but GM based in the car but I'd be hard pressed to pay twice as much to say it had a 12 bolt in it.
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65 LeMANS , SD performance 462ci Engine, Tremec TKX 5 speed with a 3.73 geared 8.5" 10 bolt |
#20
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I found myself in a similar spot with my current project. The Moser rep I worked with pointed out that the cost of a 35 spline 9" with all the upgrades and a Truetrac diff was a bit less than the best 12 bolt they could build, while being far stronger and offering easier paths to good rear brakes. I have no regrets. If you can get past the appearance and/or stigma, go with a 9". Quick Performance would be a better budget option than Moser, but I've never dealt with them.
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