Boattail Riv + 575HP + Built 10 Bolt + Slicks = ?

Discussion in 'Got gears?' started by 71GSX455-4SPD, Jan 4, 2020.

  1. 71GSX455-4SPD

    71GSX455-4SPD Nick Serwo Magic Car

    Trying to figure out a way to go rear-wise in my ‘72 Rivvy that’s getting a stout 470 stroker that Nick Servo is building. It will be a street strip car, with mostly street use. In order to make best use of the power the engine will produce in such a heavy car, the thought is to go with an OD trans in order to use a 4.10 gear or so.

    Although primarily a street car, I don’t want to be afraid to put a pair of slicks on it for occasional strip use. I’ve been looking at a Ford 9” application, but certainly an expensive route. I’ve also been reading about a lot of guys using the corporate 10 bolt rear with upgraded axles and a girdle that seem to be holding up under a lot of load, but most applications in lighter cars. Thoughts on whether or not a 10 bolt properly built would survive in the application I’ve outlined?

  2. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    10 bolt rears were used in trucks but the 575 HP with possibly 600+ ft lbs of torque with slicks is the wild card question.:eek:

    If you still have loads of low end torque(depending on cam choice?) the 4.10 gears may be to much? With regular tires on the street you may not be able to pussyfoot the go peddle enough to keep the tires from spinning when taking off from every light?(especially with a loose converter):eek:
  3. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    10 bolt rears were used in trucks but the 575 HP with possibly 600+ ft lbs of torque with slicks is the wild card question.:eek:

    If you still have loads of low end torque(depending on cam choice?) the 4.10 gears may be to much? With regular tires on the street you may not be able to pussyfoot the go peddle enough to keep the tires from spinning when taking off from every light?(especially with a loose converter):eek:
  4. telriv

    telriv Well-Known Member

    An 8.8" Ford from a Bronco should work IF built properly & is lighter than a 9". Of course an axle upgrade would be needed. My son is using one in the Mustang with about 12-1300 HP with a Powerglide & 3.23 gears. Also comes with disc brakes for another plus.
    And instead of a 200/4R, 700R4 which would need to be properly built for the HP, weight & slicks would be pretty costly by itself along with the installation of such. Why not stay with a proven reliable trans. (TH400) & put a Gear Venders on the back of it???

    Just my thoughts.

    Tom T.
    300sbb_overkill likes this.
  5. 71GSX455-4SPD

    71GSX455-4SPD Nick Serwo Magic Car

    Thanks for the responses Derek and Tom.

    The engine builder thinks it’ll need more gear to make the most of the combo. I have a factory 3.42 posi (in fact I have two of theses rare rears!). Derek, I suspect you will be correct in that it will be a handful. Definitely will need some decent street rubber and not forget what’s under the hood and put it to the floor. I have a rebuilt TH400 with a Switch Pitch pump and a SP converter built by Jim W. One option is to put a GV behind it. Nick is thinking 4l80 instead, so not decided yet.

    Tom, the 8.8 sounds intriguing, your son is certainly putting a lot of power through it. Did he do the fab work on it? If I found one the right width I’d have to have spring perches and control arm brackets dabbed and welded on. That’s where the $$ start coming in. I’ll save up and spend it if other options are not available. Thanks again!
  6. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    A quick performance 9" is hard to beat. I was able to get one under my skylark for under 2k. I did use stock f-150 drums though.
  7. Briz

    Briz Platinum Level Contributor

    For the money and support I'd go with the 9" Ford. Lots of aftermarket support and more choices in gear ratio than you'll ever need.
  8. hugger

    hugger Well-Known Member

    The 10bolt will be approaching its limits with that much weight and power,.I'd go with a QP 9in, Id do the fabricated housing with 1/4in tubes just to be safe,..I would also use a good case with a Daytona support,..a standard N case with the standard support would be borderline imo,.
  9. 71GSX455-4SPD

    71GSX455-4SPD Nick Serwo Magic Car

    Thanks Joe and Briz. I spec’d out an A-body rear on the quick performance website and it comes in around $2500 with some appropriate upgrades. That’s with drum brakes as well.

    9" Ford Complete Rearend GM A-Body 68-72
    View/Hide options
    Housing Upgrades: Drain & Fill Plugs w/ Jack Pad $55.00
    1/4" Heavy Walled Axle Tube $30.00
    Wheel Bolt Pattern: 5x5" (Big Chevy)
    Wheel Stud Size: 1/2"-20 x 3" (Long)
    Center Section Gear Ratio: 4.11
    Center Section Traction Device: 31 Spline Detroit Style Locker - $155.00
    Center Section Upgrade (450-650 HP): Yukon Pro N case, Daytona Pinion Support, Billet Yoke (for 450-650 HP) - $350.00
    Brake Kit Options: 11" Drum Brakes

    Might be the answer. I know I’d have to ask them to build it to the Riviera width, so likely an up charge from the $2500 as above.
    Last edited: Jan 4, 2020
  10. 71GSX455-4SPD

    71GSX455-4SPD Nick Serwo Magic Car

    Hugger, I didn’t see your reply until I posted mine. Do you think as selected it would do the trick? It’s not fabricated, but 1/4 wall tubing and a heavier duty chunk.
  11. hugger

    hugger Well-Known Member

    The only reason I say fabricated is it's only $100 more than the big web but has a thicker flange that's the biggest advantage look cool

    I'd do 33 spline minimum

    Get the adjustable lower mounts also,.that will really make getting the instant center where you need it
  12. 71GSX455-4SPD

    71GSX455-4SPD Nick Serwo Magic Car

    Gotcha, thank you
  13. telriv

    telriv Well-Known Member

    All that I can tell you Ken is that he controls how much power can be put down by messing with timing & boost. The car is about 3200pds. & the driver is about 310 so were talking about 3500pds. in total. It's held together now for 3 1/2 seasons. They use the trans. brake & lifts the left front inches. At about 20-30 feet out is when the power comes on & does the 60ft. in 1.13 with the REAR tires as the front are held until about 100-150ft. So far they've run a best of 7.78ET@177MPH.
    Billy built all the suspension, etc. Welded all his own made bracketry We can talk tomorrow.
  14. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    I for one am not that impressed with the Ford 9" rears.

    I built a little 383 sbc for a friend of mind that he destroyed 2 center sections and then twisted the two 33 spline axles it had! The sbc was around 580 HP with about 530 ft lbs of torque so if a little sbc can do that to a Ford 9" what is the 575 HP with around 600 ft lb BBB with slicks going to do to it?:eek:

    After the 40 spline axles and heavy duty performance center section were installed the rear end problems were gone but he started twisting transmission input shafts!:rolleyes:

    The thing I couldn't understand was how that cut and welded seasoned and rusted sbb 350/th350 driveshaft didn't break before the axle or trans parts!:mad::eek::confused:o_O:rolleyes: The driveshaft was supposed to be the weak link!:(

    Now he got rid of the TH350 and installed a TH400 with a stock converter that I'm thinking it ballooned and took out the thrust bearing!:mad: Oh, well it lasted 5 seasons of very intense Silver Lake Sand Dune driving breaking just about everything behind it except that dam driveshaft! To date IIRC he went through 4 powerglide transmissions, 3 TH350 transmissions, 2 Ford 9" center sections and 2 axles before he lost the thrust bearing after he went with a TH400.
    Last edited: Jan 5, 2020
  15. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    I forgot to mention I bought a complete used F-150 rear for 200 bucks. It had i scavenged the brakes and center section out of it. It had 4.11s so I added a posi unit and called it.. been pretty deep into the 11s with a 4 speed with it. It worked out pretty good. I bought the drums from quick performance that were drilled 5x4.75

    If you don't want to junkyard gears you can always shop for used center section. They are everywhere.
  16. monzaz

    monzaz Jim

    I would not hesitate to use a 8.5 rear with bolt in moser axles and 30 spline axles true trac or 33 spline with a full spool if the street is minimal
    I would cut the ends off and install Moser Billet end to support 1.533 axles and Larger O/P 3.150 axle bearings (then you can choose the end you want for the brakes you want to run...Impala 11" drum or Late model ford end torino or even small chevelle /camaro end with disc brakes?? ) The ends the 1971- 1976 full size car has , gives you no choice in brakes at all. No one makes disc brakes for that end.

    8.8 or 8.5 are in the same boat... ring & pinion gear is not the problem.... 8.8 Ford Posi is a piece of junk compared to the 8.5 stock posi ...BUT would not use either posi in this application. I do not know why people think because something has Ford in the name it must be good. If you are trying to make a Stock third member 9" do the job, forget about it. spend more and get aftermarket stuff. This is not a place to cut corners.
    AFTERmarket OR do not do 9"
    The disadvantage you have is WEIGHT of the vehicle (tank riv) and the high torque (Buick Monster)...That combo breaks parts when the car hooks. As long as the heavy car ears street shoes you should not have a problem...IT IS when the sticky shoes get put on where the hurt happens...

    There is my 2 cents from a rear differential guy.

    Last edited: Jan 7, 2020
    Dano and 300sbb_overkill like this.
  17. No Lift

    No Lift Platinum Level Contributor

    I'm running a 8.5 10 bolt in my '76 at 4250 lbs, 10.83@125 street car. Low 1.50's 60'. Detroit TrueTrac and 30 spline Moser axles. The 28 spline factory axles were starting to twist high 11's. I've made a load of runs on it and it has been good but I did crack a tooth on the 4.10's two years ago. I can't complain because of the beatings I've laid on it.

    On the other hand Tom Wagner runs 10.80@125 in his '69 Wildcat(bench seat) street car with a 9" with aftermarket parts for sure, 4.10 or 4.33. But then he runs the factory big rear with 3.90's in his heavier '70 Wildcat(bucket seats) that runs 11.90's. You might want to PM him on where he had the 9" set up to fit.
    lsSkylark likes this.
  18. 71GSX455-4SPD

    71GSX455-4SPD Nick Serwo Magic Car

    Thanks guys for the additional input. It sounds like stronger aftermarket parts, regardless of rear, are highly recommended to get any kind of expectation of longevity. I’m also getting that making sure the rear is setup by someone who is both thorough and spends the time to more or less “blueprint” it, is a must. I also get that putting a big power motor in a big heavy car is pushing the limits of the entire driveline. I do want to put slicks on it a few times a year at the track and recognize I might blow it up at some point. I like the idea of brake options with end changes on the 8.5 or the 9 (I think I’m reading that) to offer brake options.

    I’ve got a little thinking to do and then pick a direction and a builder. I’ll also contact Tom Wagoner as suggested.

    I really appreciate all the input. Ken
  19. philip roitman

    philip roitman Well-Known Member

    My 9 inch Ford style Moser rear built for my yellow '73 racer that Tom Q owns now was only in the low $2,ooo. price range. It was 15 years ago, but shouldn't be that much more now. Full 3.90 rear with housing, axles etc. I did eventually add a H & R parts n Stuff full rear suspension. On the other hand my '73 Factory Stock car (Buick heads, exhaust manifolds and Carb) has a stock rear end with 3.73's and Moser axles. It has worked for as long a time with no problems. 550 HP and 615TQ, the previous now spare motor was just a little less than that. My car weighs 4100LB's without me in the car. P.S. It runs great on the street with no spinning the tires problems, unless of course I want to! LOL
    Last edited: Jan 9, 2020
  20. 71rivera

    71rivera Platinum Level Contributor

    I will be interested in hearing what you come up with!
    I am doing a similar build with my 72' Riviera.
    I was thinking a strange S60....
    I kind of didn't know what direction to go, so I welded a BOP 12 bolt and have not had the guts to try it out.

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