Best High-po Tranny?

Discussion in '1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-' started by 91redFox, Jan 20, 2014.


  1. Shoomakan

    Shoomakan New Member

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    Just read all of this. Very interesting and thank you. If what I understood is true, the preference seems to be TKO600, T56, and G-Force coming in last.

    I'd also like to say that one of the reasons I love my BMW is because the Germans know how to design drive line components.

    I mentioned that I might be using a Getrag 265 on my 5.0 when I put it together. For those who aren't in the know, it's a cheap little BMW tranny that came mostly on their 6 cylinder cars of the 80's and 90's. I believe the official torque rating was 360 ft/lb, and there are many turbo BMW's out there putting out 50% more torque than that and still using their factory G265.

    The 6 speed on my 540i is rated for 420NM and is famous for handling enormous amounts of abuse. The king of the hill would be the G560, the V12 6 speed that only came on the 850i. Those things are rated at 560+NM (more than the Supra 2JZ transmission). You can imagine what they can handle.

    My entire point is, since Getrag 265's are cheap and plentiful, someone REALLY should be working to putting them on a Fox. They'll handle the torque of a NA 5.0 very easily, and I imagine it'll take a well boosted 5.0 with slicks to shatter one to pieces. And when that happens.. $150 later and you have another one.

    Added advantages of this tranny are a removable bell housing, which makes attaching it to other engines easier than you would think, as well as good gear ratios (but a much shallower OD. I know you Americans love your OD gears, but BMW/Getrag OD's are around ~0.80).

    Unfortunately, you'll have to deal with modifying the tailshaft of the tranny as it is designed to bolt to an IRS rear. Unless you're as lucky as I am... I found a couple of old Opel Manta G265's, which are special because that Opel is a live axle rear... :)

    I'd love to discuss this further and find new options and ideas. For example, not one person said anything good about the Cobra T5 Z transmission that came on the latest and greatest Fox. Are they really that bad?
    Last edited: Jun 25, 2014
    #61
  2. FastDriver

    FastDriver Mod Dude

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    slight upgrade. Not worth the hassle of locating and paying for one. If memory serves (and it unfortunately doesn't usually serve that well), the stock World Class T5 was rated at 300 ft-lbs and the T5Z was rated at 330. Not a big difference.

    IF this tranny is as stout as you say, it's a reasonable idea, but going down uncharted trails always lead to headaches. Some stuff that comes to mind: input shaft diamater and length for engagement which may require a custom bellhousing and at minimum an adapter plate, throw out bearing attachment on the Getrag, pilot bearing engagement and fit, shifter fitment, slip yoke availability, drive shaft length, and gear ratios as you mentioned.

    This is going to work out to be expensive. But if the prices you quoted are accurate and they are readily available, and you anticipate needing to replace it frequently, it's a reasonable idea. All that said, it's not something I would go for as direct plug and play transmissions have better torque ratings.

    And again, "hi-po" is completely subjective. For my car, I'd need something serious to hold up for long. That said, I've put over 800 rwhp through my little TKO, which was rated at only 450 ft-lbs.
    #62
  3. revhead347

    revhead347 I have face herpes.

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    We have a Getrag 265 in our track car. Apples and Oranges. Driveline is the rope in a tug of war. At one end you have the torque of the engine, at the other you have weight of the car and traction of the tire. A little 265 is fine in a 2800lb E30 with a 2.5L 6 cylinder and street tires. No matter how much power you get out of the engine, the tires will start spinning long before there is any real strain on the transmission. If you put that spindly little transmission in a 3500lb Mustang with slicks on the back and 500 ftlb of torque it's going to scatter. Not to mention it has a rubber damper inside of the rear harmonic damper. That little piece of rubber would tear right off on a hard launch. There is no magic in a transmission. The only way to get it stronger is to run bigger gears, bigger bearings, and a thicker case.

    Kurt
    #63
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  4. Shoomakan

    Shoomakan New Member

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    I completely agree with you, but you're mistaken on application. The G265 was also used on an E34 535i, which is ~600 pounds heavier than a Foxbody Mustang. Boosted 535i's regularly make over 400hp, on a bigger, heavier car. And they rarely scatter.

    Is the rubber unit you're talking about the guibo? Because I know of at least one 800 horsepower E34 525i that's still using the stock unit. It's a beautiful car, by the way. Check it out:

    View: https://www.youtube.com/watch?v=CBaG6fUU0GE


    That guy was/is on the stock 5 speed that came on the car. He regularly drags it, and has quite a few pics online with massive 15" slicks on the back.

    I know another guy, here, local, who used the same G265 I found. He attached it to a twin turbo 8.2 liter GM V8. The tranny shat itself about a month later, at the dyno. The car twisted its driveshaft, diff, and rear subframe apart along with the tranny. Right before it burst, the dynograph indicated 860NM of torque at the WHEELS (600whp/860NM@4600RPM:p). It's obviously not made to handle that kind of abuse.

    My entire point was, it is a significantly stronger transmission that a stock/WC/Z T5. I never said it'll handle a highly boosted stroker Windsor motor, I merely said it'll handle a moderately boosted 302.

    Here's a picture of the car I spoke of. It's a 1979 Trans AM, 8.2 liter twin turbo marine GM engine (450hp stock/NA), currently running a stock Muncie 4 speed. It's chewed up 2 of those already, by the way. He's running MS1, twin GT 35's, set at 8 psi.
    2014-03-26 14.42.07.jpg
    #64
  5. revhead347

    revhead347 I have face herpes.

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    Alright, I'm starting to come around on the idea. If not for a slicks car at least for a street car. I guess it would depend quite a bit on gear ratios. Going to need at least a .60:1 6th gear to make it worthwhile with a domestic V8.

    Kurt
    #65
  6. revhead347

    revhead347 I have face herpes.

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    Ok, nevermind. All of those BMW 6 speeds start with a 4.25:1 1st gear and end with a 0.83:1 6th gear. That is just not going to work for the Mustang enthusiast.

    Kurt
    #66
  7. Shoomakan

    Shoomakan New Member

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    Yeah, I kinda mentioned that in my first post. :p Even their 5 speeds have a ~0.80 FD. I have a 3.73 final drive on my 540i, and at 100kph, it's turning in 2500 rpm's. :)

    The reason you guys like those long ass FD's is because you can run a 3.73 and still have decent highway RPM/mileage at 60mph, I imagine. The short gearing on my car never bothered me, as the longest highway in Lebanon is about ~100km long. You're never on the highway for more than 2 hours. Lots of mountain roads and twisties, though. Short gearing is a blessing there.
    #67
  8. KhanTyranitar

    KhanTyranitar Member

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    I don't get this, a stock T5 will handle your power goals just fine. You just need a stronger than stock clutch and you are good.
    #68
  9. FastDriver

    FastDriver Mod Dude

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    Not in my experience. I blew up a stock T5 with only 320 rwhp on the street on drag radials.
    #69
  10. revhead347

    revhead347 I have face herpes.

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    +1. It's pretty easy to break a T5 with a stock engine.

    Kurt
    #70
  11. blackNHcoupe

    blackNHcoupe New Member

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    Let me start by saying I'm not a newbie. I was registered back in 2000 but haven't been here in many years.

    There is a lot of bad info about t5's. How many people have actually broke a T5 case? They are tougher than the 3550 and TKO cases. Not saying they don't break just saying its not the weak link until you are putting a lot of torque to it. The first thing you can do to a stock T5 to make it last is tighten up the end play to +.001. That goes along way. Second traction isn't as hard on a T5 as wheel hop is. Third is a moderate rate pressure plate and proper cable adjustment .

    The G-force comes in a few different configurations. Heli-cut synchroed, heli-cut dog ring and straight cut dog ring. The straight cut is the stronger of the group but wouldn't consider it a street trans. Same with any dog ring trans. What I dont like about the G-Force synchroed trans is that it uses a stock Z-spec first gear and I have seen several 3rd gear failures. Its a good upgrade to a point but I wouldn't put one in my car.

    To me the Astro A5 with upgraded mainshaft is hands down the best all around choice for a car making 500whp or less . If it makes you sleep better at night put it in the G-Force case. I done several of these and never had 1 fail and only have heard of 1 failing. I'm sure their are more but I just haven't heard about them. Shifts silk smooth up over 6000 rpm ,its quiet and a tough little box.

    I'm not a big fan of the TKO. The have notorious shifting problems and not much stronger (if any) than the A5. If you run a faceplated one in a race car than that's another story. At the point I would have to consider more than an A5 for a street car I would skip over the TKO600 and go with the T56 magnum.
    #71

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