Best High-po Tranny?

Shoomakan · Jun 25, 2014

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?

FastDriver · Jun 25, 2014

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.

revhead347 · Jun 25, 2014

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

Shoomakan · Jun 26, 2014

revhead347 said:
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

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). 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.

revhead347 · Jun 27, 2014

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

revhead347 · Jun 27, 2014

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

Shoomakan · Jun 28, 2014

revhead347 said:
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

Yeah, I kinda mentioned that in my first post. 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.

KhanTyranitar · Jul 13, 2014

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.

FastDriver · Jul 14, 2014

KhanTyranitar said:
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.

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

revhead347 · Jul 16, 2014

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

Kurt

blackNHcoupe · Jul 30, 2014

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.

revhead347 · Jul 31, 2014

Lots of stuff I disagree with there. TKOs crack more because they are more popular in drag racing in higher hp cars. The only reason a T5 case doesn't crack as often is because the cluster usually breaks first. Everything about a TKO is tougher than a T5. The case is bigger, the gears are bigger, it weighs 30lbs more. If you put a T5 shaft next to a TKO shaft on the bench, there is no doubt which one was stronger. All the stuff they do with the gear ratios and the hardening on the T5s is just a band aid for an undersized transmission. The shifting problems in the TKO are easy to fix. It was never originally intended to be a drag racing transmission, it just happens to do well in that application when set up correctly. The case cracking problems can be corrected with a Swarr girdle.

For a street car, I agree, the T56 magnum is the way to go. However, it's damn near twice the money for a Mustang. For drag racing, it shifts slower. If you shift it as fast as the TKO, it's going to break. It has more teeth on the engagement surface, and was never intended to be shifted at any speed. You can do a short google search to see all the engagement failures people are having with their TR6060s in new Camaros when they try and race them.

Kurt

blackNHcoupe · Jul 31, 2014

"TKOs crack more because they are more popular in drag racing in higher hp cars."

That is not true at all. The Tremec case has been upgraded 4 times. I have seen every style crack. Bigger does't always equate to stronger. Because of its size the case is very thin in areas where it needs to be the thickest. The larger gear spacing that allows larger gears actually puts more stress on the case .Plenty of lower power street car have come to me with cracked and broken cases.The latest case is far less prone but does have the same weak area. Does the TKO600 have more potential ? Yes.. But not out of the box ( ie more $$$).That is why I would go right to the t56, BTW it is not even close to double the cost. I will take the A5 over it any day!
I'm going off my 20yrs experience which is well over 100 builds,rebuilds,repaired and performance upgrades to all of the above. I'm not going off what I have read or what I have heard from another builder.

Noobz347 · Jul 31, 2014

revhead347 said:
Lots of stuff I disagree with there. TKOs crack more because they are more popular in drag racing in higher hp cars. The only reason a T5 case doesn't crack as often is because the cluster usually breaks first. Everything about a TKO is tougher than a T5. The case is bigger, the gears are bigger, it weighs 30lbs more. If you put a T5 shaft next to a TKO shaft on the bench, there is no doubt which one was stronger. All the stuff they do with the gear ratios and the hardening on the T5s is just a band aid for an undersized transmission. The shifting problems in the TKO are easy to fix. It was never originally intended to be a drag racing transmission, it just happens to do well in that application when set up correctly. The case cracking problems can be corrected with a Swarr girdle.

For a street car, I agree, the T56 magnum is the way to go. However, it's damn near twice the money for a Mustang. For drag racing, it shifts slower. If you shift it as fast as the TKO, it's going to break. It has more teeth on the engagement surface, and was never intended to be shifted at any speed. You can do a short google search to see all the engagement failures people are having with their TR6060s in new Camaros when they try and race them.

Kurt

blackNHcoupe said:
"TKOs crack more because they are more popular in drag racing in higher hp cars."

That is not true at all. The Tremec case has been upgraded 4 times. I have seen every style crack. Bigger does't always equate to stronger. Because of its size the case is very thin in areas where it needs to be the thickest. The larger gear spacing that allows larger gears actually puts more stress on the case .Plenty of lower power street car have come to me with cracked and broken cases.The latest case is far less prone but does have the same weak area. Does the TKO600 have more potential ? Yes.. But not out of the box ( ie more $$$).That is why I would go right to the t56, BTW it is not even close to double the cost. I will take the A5 over it any day!
I'm going off my 20yrs experience which is well over 100 builds,rebuilds,repaired and performance upgrades to all of the above. I'm not going off what I have read or what I have heard from another builder.

I love to see this stuff. I'm already familiar with Kurt's reputation and knowledge. He's been here quite a while. blackNHcoupe appears to have some valid argument and obviously knows something of the topic as well...

So two guys that I believe know quite a bit about the topic who disagree. ^THIS^ is how we learn stuff.

I had a feeling that this thread would turn into something good.

Even though you been here since 2004.
Welcome aboard blackNHcoupe.

revhead347 · Jul 31, 2014

I just priced out a Magnum for a customer. Over $4k in parts alone. Not quite double but damn close.

You have some valid points. The front side of the TKO case is too thin for sure. Seen quite a few crack there. I'll agree to disagree on the rest. If I had a solid amount of money on a race, I would rather have a TKO in the car than any of the T5s. You can crack the case and still win. If you blow the teeth off the gear in a T5 you are done.

Kurt

FastDriver · Aug 3, 2014

blackNHcoupe, out of curiosity, who are you, and where are you from? I assumed you run a performance shop or something? Your name is reminiscent of usernames I've seen from Michael Bell of Dayton Performance.

91redFox · Aug 4, 2014

Thanks for all the interest and information in this thread guys! Really appreciate all of the help. As of now, my t5 is in need of a clutch. Whats y'alls take on the Centerforce dual friction? I know a lot of guys nowadays like Exedy and Spec, but my dad used is a firm believer in the CF (he used them in his 66) and I've heard some good things about the strength and drivability of the DF.

Any further knowledge on these clutches?

FastDriver · Aug 4, 2014

Nothing wrong with CF or spec. I've used both without issue.

blackNHcoupe · Aug 4, 2014

FastDriver said:
blackNHcoupe, out of curiosity, who are you, and where are you from? I assumed you run a performance shop or something? Your name is reminiscent of usernames I've seen from Michael Bell of Dayton Performance.

My name is Chris Hatch. I live in Ct but lived in New Hampshire for 10yrs. Hence the NH. I don't have a shop but for a long while had been doing enough on the side that I could have made the jump to a full time business. I am an authorized Astro dealer . I built some of the first few A5 transmissions and have done some warranty work for them as well. I also have worked with Liberty and G-Force on other projects. All of my work has been referrals and word of mouth.

blackNHcoupe · Aug 4, 2014

91redFox said:
Thanks for all the interest and information in this thread guys! Really appreciate all of the help. As of now, my t5 is in need of a clutch. Whats y'alls take on the Centerforce dual friction? I know a lot of guys nowadays like Exedy and Spec, but my dad used is a firm believer in the CF (he used them in his 66) and I've heard some good things about the strength and drivability of the DF.

Any further knowledge on these clutches?

I like the DF disc with a King Cobra style PP.

Best High-po Tranny?

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