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  1. #1
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    Default Flywheel and clutch recommendations

    I'm just finishing up my 351 build and I'm looking for an SFI rated flywheel and a clutch. I don't have any experience buying anything other than oem replacement parts and I was wanting to know what you guys are using. Thanks in advance!

  2. #2
    Moderator wraithracing's Avatar
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    Personally I like Fidanza Flywheels and Spec Clutches.

    Ford Racing Flywheel works just fine too.

    Center Force Clutches are good too.

    Bottom line is how much power are you planning on making and how much is your budget. That will determine a lot of your options right there.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
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    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
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    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  3. #3
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    I probably wont go over 500 horsepower. I'm trying to spend less than $700 on a new setup. The cheapest flywheel I could find on summit that is SFI rated is the 17lb Spec flywheel. I was considering pairing it with a Spec stage 2 clutch since people said they're supposed to last longer and be more durable. I'm not sure how true that is. I looked at the Fidanza flywheels they seemed out of my price range.

    I just wanted to hear from some current peoples experiences with products before I placed an order. I've read through a lot of older posts about Spec products. Some people have had mixed results but a lot of the threads were over 5 years ago.

  4. #4
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    I`ve been running McLeod aluminum flywheels and adjustable "soft Lok" clutches for over 20 years now, both on my FE 427 and 428s, and my 302 and 331 SBFs. Work great for racing, super light pedal feel, but way over 700 bucks, and likely not the best choice for a street car.
    1978 Fairmont 2 door sedan, 428CJ 4speed. 9.972ET@132.54mph. 1.29 60 foot
    Replaced the FE big block with my 331/4 speed in my Fairmont, best 10.24ET @128 MPH.
    1985 Mustang LX hatchback NHRA Stock Eliminator 302 4 speed best in legal trim 12.31@107 mph, but has gone 11.42@115 with aftermarket intake, carb, and iron Windsor Jr. heads.New for 2012! 331 cube SB Ford, AFR 185 heads, solid flat tappet cam, pump gas; 10.296ET@128.71 mph, 1.37 60 foot.
    1979 Zephyr Z7, all original 302 auto, 2nd owner.

  5. #5
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    Does anyone know if the 83 T5 has the same input shaft diameter as the later model T5 units?

  6. #6
    FEP Member bkm's Avatar
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    Speaking from experience, spec clutches and T5's don't live well together. If this is a stock gearset T5, you need a softer clutch to keep the transmission somewhat happy. I always had good luck keeping T5's around little longer with a king cobra disc. Let the clutch be the fusible link between engine and transmission.

  7. #7
    Moderator wraithracing's Avatar
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    Quote Originally Posted by Jmac509 View Post
    Does anyone know if the 83 T5 has the same input shaft diameter as the later model T5 units?
    Are you referring to the pilot bearing inner diameter? If so Yes.

    Just keep in mind that the 83/84 T5 are not World Class units. The 85-95 V8 and the 87-93 4 cyl T5's are World Class so that changes many of the parts and pieces inside the transmission.

    If you are planning on 500 HP, I can guarantee a stock 83 T5 will not last long behind that unless you baby the heck out of it. Not sure if upgrading the 83 T5 is worth the trouble or even an option not being a W/C transmission. I would recommend considering a different transmission before worrying about the clutch and flywheel setup.

    Also if this is a street car, I would seriously consider a steel or billet steel flywheel. The extra mass can help smooth out an idle and help get the car moving in regular driving. If this is more strip/race oriented then the Aluminum or lightweight flywheels will help the engine accelerate and are a great option.

    Also good advice by BKM in regards to using the clutch as the fusible link between the engine and transmission. Good Luck!
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
    1984 SVO Still Waiting Restoration
    1986 GT Under going Wide Body Conversion Currently

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  8. #8
    FEP Super Member erratic50's Avatar
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    A lot of the high end gear sets designed to withstand big power use a 26 spline input shaft, not a 10 spline

    solve your transmission needs based upon power level you will have now and I to the future first then worry about a clutch!

    I bought a clutch kit for my 85 build then pretty much went crazy. I threw an Airgap intake at it then let my buddy talk me into throwing AL heads at it. And another talk me into an FTI custom cam. Then I went to a stroker.... then when that shortblock go dropped a Dart based big bore stroker. And that’s even before the the beast was assembled!

    Gforce or Astro have gear sets and upgraded cases and mid section braces and one steel piece bearing retainers, etc. the stuff needed to make a T5 survive behind 600+ ft lbs of torque.

    But don’t forget about the rearend. You will need a well built 8.8 at minimum to carry the load. Add slicks and abusive driving it’s housing braces and housing ends with bigger bearings and 31 spline axles. or even just going to a full on Ford 9” build

    Dont forget about your suspension. Battle boxes, MM upper and lower control arms or even a torque arm. Do it right or do it twice.

    And please tell us you have weld in subframe connectors already

  9. #9
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    Right now I'm just trying to finish the motor. I don't plan on doing anything but tooling around until I get the rest of the build done. You do bring up a good point though, all of the aftermarket transmissions are 26 spline and getting a stage 2 clutch in 10 spline would be counter productive. I'm going to stick with the stage 1 or it sounds like rockauto carries the king cobra clutch under the valeo name.

    Good call!

    As far as suspension goes, I'm trying to figure out what the best K member would be for the 351 swap in terms of header and steering shaft clearance. Then figure out the rest of the suspension around that.

    I've read about people spending more money upgrading there T5 than it would cost to buy a TR6060/Magnum or TKO. The next step will most likely be a Tremec Magnum and 8.8" or 9"

  10. #10
    FEP Super Member erratic50's Avatar
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    If memory serves, I have invested around $1700 —all in — to have a Gforce equipped T5 built with mid brace and one piece Astro bearing retainer. The build holds around 600-650 ft lbs

    i went to a 0.59:1 overdrive so I can achieve a decent cruising RPM with 3.55 rear gears. The same as I’d see with 3.08 and a stock 0.68:1. 5th is not as strong as 1-4 but if I haven’t figured out who’s boss by 7000 in 4th (around 145 mph) then the other car can have it. Lol

    Upgraded T5’s are lighter, fit better, and shift better at high RPM.

    People forget about costs like bellhousing changes, wiring changes, mount changes, driveshaft changes, shifter changes, etc. Doing them right does add up.

    If 600-650 past 7000 isn’t enough..... look towards a viper spec T56 kit or build you an A5. The A5 is basically using the top shelf Astro T5 gear set in a purpose built case straight from Astro.

    A light flywheel, soft clutch, and low (numerically higher) rear gears can help keep a transmission alive. Just make sure you don’t have ANY wheel hop as that will kill the trans faster than anything.

    Good luck with your build!
    Last edited by erratic50; 03-24-2019 at 10:12 PM.

  11. #11
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    What parts do you need to upgrade the T5? I see the GeForce T5 listed up on Jegs for $3400 for a stock ford case version and $3700 for the heavy duty case version.

    I don't plan on producing more than 600 horsepower and if upgrading the T5 is the cheapest, easiest, and most reliable option I'm interested.

    When I mentioned upgrading my T5 to the guy at the machine shop he suggested I switch to a top loader 4 speed for better reliability.

  12. #12
    FEP Super Member erratic50's Avatar
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    Best bet is to contact Gforce and talk through it. The nice part is the range of gear ratios they offer.

    https://www.gforcetransmissions.com/...treet-5-Speed/

    Astro is a direct competitor and has a very similar product available.

  13. #13
    FEP Member bkm's Avatar
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    I considered going the route of a top loader, but here are a few things to consider:

    Obviously no overdrive
    Expensive bellhousing for cable clutch
    Heavy cast iron
    Shifters are around $500 for a new Hurst that has to be modified for a Foxbody
    A nice one can be hard to find

    But, they are very strong and parts are plentiful.

    By the time you do it right, your in used A5/TKO territory and will have overdrive.

  14. #14
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    I will have to give astro and geforce a call and consider that in my plan. It's good to hear people having good luck with the T5. Thanks for the suggestion! My brief research I did previously lead me to the idea that the T5 was hopelessly unreliable for track use. Once I get to that point I'll probably start another thread about transmissions. Thanks for the suggestions everyone, I appreciate it!

  15. #15

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    I would avoid G-Force completely. In our experience, their T5 gearsets are weaker than stock gearsets. Their expensive case doesn't really have any affect and they absolutely do not stand behind their product in any way. Do a quick Google search for G-force broken 3rd gear. I know that there are some people who claim to have 100+ drag strip passes without problems, but for every one of those people I can find five, who had 3rd gear fail.

    I would use a TKO500/600 and have it modified if you are going to shift above 6,500 rpm. No amount of marketing can ever make up for how much larger the gears are in it over a T5. I agree that it doesn't shift as well, but it is much more reliable.

    BTW, it doesn't matter how much power the engine makes when looking at clutches and transmissions, it is the torque that is going to break them or make them slip.
    Jack Hidley
    Maximum Motorsports Tech Support

  16. #16
    FEP Super Member xctasy's Avatar
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    Quote Originally Posted by Jmac509 View Post
    What parts do you need to upgrade the T5? I see the GeForce T5 listed up on Jegs for $3400 for a stock ford case version and $3700 for the heavy duty case version.

    I don't plan on producing more than 600 horsepower and if upgrading the T5 is the cheapest, easiest, and most reliable option I'm interested.

    When I mentioned upgrading my T5 to the guy at the machine shop he suggested I switch to a top loader 4 speed for better reliability.
    Good advice from all here. JH, bmk both excellent additional points.


    My take on it is the same as it was in 1988 when I was invloved in a 375 hp net 351C rebuild in a heavy 1971 Australian Falcon.

    My adive then was Top Loader 4 speed.

    Anytime you add anything other than a Gear Vendors over-drive, you loose torque capacity with 5 and 6 speed gearboxes. To get 5 speeds reliable, it took 10 years, and a T5 is still much lighter than a TopLoader.

    For Six speeds and the better heavier duty big block capable 5 and 6 speeds, your into adding double sychros and upgrading cases, mainshafts, and gears. In anything other than a mass produced gearbox destined for a Ford, Mopar or GM product, a custom non mass produced box won't give you a certainty of extra strength. Just like good power steering units, mass production forces quality into the process.

    One thing everyone must learn form Detriot engineers is that mass producing creates quality, hand building creates extra risks.

    Quite why the better versions of the Top Loader reign supreme is Ford win at all costs Total Performance focus after opting out of the AMA ban in 1962. Everything Ford cast from 1962 to early 1969 is gold plated. Right about the 69 modle year, the realities of business and the quality price tradeoff, and weight down grade started happening, first with little six cylinder engine blocks, then shell moulded Cleveland era small blocks (Windsor 351's were pretty good for the first 5 years), and then the TopLoader and 8 and 9" axle to 7.5/8.7 and other kinds of downgrades happened about 1977.

    Example:

    When Ford had Tremec turn the 1967 3.03 9 bolt 3 speed TopLoader into a 1977-1983 4 speed over drive, it went from being 14 second, 100 mph ET 320 hp, 427 lb-ft capable gearbox, to one that would break under 15 second and 95 mph ET's with just 175 hp and 265 lb-ft of torque.

    The Top Loader 4 speed is the strongest 3.03 layshaft center spacing gearbox around for the money anywhere. Still. A bull nose varient with Liberty cut sychros won't break easily.

    Ford mass produced a better Top Loading mousetrap.

    Its basically like the old Jaguar fully synchro XK-E Moss 4 speed gearbox, which was found behind 282 to 326 lb-ft net torque 5.3 liter Jaguars from 1971 untill 1977. Only the TopLoader 4 speed , in its best Big Block forms, is an over 450 lb-ft net trans. Its one heck of a lot stronger than anything except the Aston Martin V8 ZF 5 speed gearbox. British Leyland and Land Rover made the old Jag box into a LT77 or R380 Five speed for Morgans, TVR's with the Buick Olds Pontiact based 3.5/3.9/4.6 engines, but it then lost torque capacity to 245 to 280 lb-ft, which is always what happens when you add an over drive top. A 33% loss in strength is always what happens.

    Fords spur into the TopLoader was when the French used production capacity from Ford's former plat to make the Pont-à-Mousson 4-speed gearbox in the Chrysler Hemi engined Facel Vega and Mopar USA used that in some 1960 Chrysler 300F's.

    Ford USA decided to up the ante, first with Borg Warner T85's and T10's, then the ultimate 3.03 TopLoader in 3 or 4 speed, short or long case configuration.

    The response from Mopar was to run a New Process behind Hemis and Wedges.

    For GM from 1957 to 1982 performance engines, it was either a T10, non Ford coded Toploader, a Muncie Rock Crusher, Super T10 or DNE 4 speed O/D or aftermarket Doug Nash 5 speed, then they went T5 like eveyone else in 1982. The brief forary in to the Saginaw/ Borg Warner T50 Porsche/Ferrari race gate from 76-80 in Vegas, Skylarks and Monza's was a reliabity failure.


    Nothing really rates, because everything went aluminum castings.

    David Kee does good business in TopLoaders because of the Quality Price and Weight trade-off of an alloy or aluminum case gearbox. Ford won't ever again spend 60's like money on cast iron stick shifts like the TopLoader, but just like FE engine blocks, one cast irn TopLoader can be rebuilt to factory spec, and be better than a lot of aftermarket gearboxes.


    Everyone says they want ratio spread, demon 4.11 axle ratios for drags, and an over drive for a 2.75:1 axle cruise home. Sure, but you pay for it in a lack of stick shift gearbox durablity.


    In a 351 Fox, a wide ratio 2.78:1 First 4 speed will work exceptionally well with a set of 3.27/3.25 to 3.08/3.00 gears and the right rolling stock, just like they did in the old late 60's and early 70's Muscle Uni body Fords.

  17. #17
    FEP Super Member xctasy's Avatar
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    One option to make a cheep reliable 6 speed is:-

    https://www.fordsix.com/viewtopic.php?f=76&t=76374

    Take a RAN 3 speed 9 bolt Top Loader.

    Get a stick shift conversion.

    Add o/d splitter switch.


    The 3.03 gear ratios for 6-cylinder Bronco/Falcon/Mustang/Maverick/Ranchero models, V8-s had taller ratios.

    First 2.99
    Second 1.75
    Third 1.00
    Reverse 3.17

    The 3.03 manual is also known as a RAN gearbox, from the casting codes on the side. Best way to id one in the car is by the casting codes.


    Take a GearVendors overdrive, a 0.78:1 ratio hike on the stock ratios above, to create a quasi TKO 6 speed.

    1st Gear: -------------------> 2.99
    2nd Gear (OD Ist): -------> 2.33
    3rd Gear: (2nd)-----------> 1.75
    4th Gear: (OD 2nd)-------> 1.37
    5th Gear: (3rd )----------> 1.00
    6th Gear: (OD 3rd)-------> 0.78

    It doesn't quite do it as a close ratio TKO 6 Speed, as the first three ratios differ by 11.3 to 4 %, but not far off...


    close ratio TKO 6 Speed
    1st Gear: 2.66;(in terms of the ratios above, 3.33) vs 2.99 11.3 % too steep (taller geared than ideal)
    2nd Gear: 1.78;(in terms of the ratios above, 2.22) vs 2.33 5% too shallow (lower geared than ideal)
    3rd Gear: 1.30;(in terms of the ratios above, 1.63) vs 1.75 7.4% too shallow (lower geared than ideal)
    4th Gear: 1.00;(in terms of the ratios above, 1.25) vs 1.37 9.6% too shallow (lower geared than ideal)
    5th Gear: 0.80;(in terms of the ratios above, 1.00) same
    6th Gear: 0.63(in terms of the ratios above, 0.79) almost the same

  18. #18
    FEP Super Member erratic50's Avatar
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    I sincerely hope the Gforce comments are untrue but I have no reason to doubt Jack’s experience.

    I was on the fence about Gforce vs Astro gear sets. The T5 builder Trey and I chose for my 85 Saleen Clone project went with Gforce based upon his luck with them on his high boost turbocharged propane powered beast that has hundreds of passes on it. Also among other builds where he’s used Gforce successfully.

  19. #19

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    For clutches, my opinion the best deal in the power range you want is a Ram Powergrip HD. Good sprung hub, thick Marcel spring, and a touch of give on a launch. I could run a full season on one with no issues (100 passes) and 3-5K street miles. For your transmission now, I might be inclined to put a rag type clutch in there (King Cobra from UPR) just until you sort out what you want in the future and let that thing sort of live.

    As someone said above, the more you race, the more you will change what you need ... I went from Ram Clutch / G Force T5 stuff and evolved into Black Magic sintered iron / billet cover with a G Force G101a behind it. Clutch protects everything and is fully adjustable for base and counter weight. Nothing I'm doing now is Cheap ($2500 clutch and $5000 transmission) but its way more race that street these days.
    Bob Myers ©

    84 Capri RS Turbo - Only a 4 banger - 1/8th 6.29@110, 1/4 9.87@137

  20. #20

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    The clutch has to be properly matched to your power level. The clutch is designed to be the weak link in the drivetrain. Specs are garbage fyi. Tons of chatter issues, and even the stage 1 is too grabby. The centerforce clutch is good, or the ram HD will work well for you if you keep that t5.

    IMO though, build it once, build it right. Stay away from the 60's garbage, top loaders etc...they're only 4 speed trannies. Today's tremec's are bullet proof. The t56 magnum is rated at 700 foot pounds, and they rate them under. You can actually get a tr6060 from a late model camaro and swap the main shaft and tail shaft and make your own t56 magnum.

    You can also find used tko 5 speeds for $800-1200 often with the clutch and everything, and those will hold massive amounts of power.

    build it once, build it right
    Jeremy
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    Entire 1986 electrical and vacuum troubleshooting manual download
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  21. #21

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    Jmac,

    Is your 351W still 28oz-in imbalance?
    Jack Hidley
    Maximum Motorsports Tech Support

  22. #22
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    I believe it is still 28 oz imbalance. I'm using the OEM crank that came with the motor. I dropped the new flywheel, clutch, pressure plate, and harmonic balancer off at the machine shop today for him to balance the rotating assembly. I ended with a new set of Probe pistons on Eagle rods so I figured since I'm getting the block line honed and I'm replacing virtually everything else I might as well get everything balanced.

  23. #23

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    I have a virtually brand new 28oz-in aluminum flywheel and clutch sitting in the garage, but you already bought some, so nevermind
    Jack Hidley
    Maximum Motorsports Tech Support

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