No lencos or jeffcos. What's the strongest manual trans you can put in one of these cars?

 

Jerico or Tex Racing 4-speed w/ magnesium case and straight-cut gears are the top of the heap for brute strength.

Start thinking $5K without the bellhousing, crossmember, clutch, driveshaft, etc.

Edit: looking at Jerico's website it appears they have a 5-speed trans also, and Lou Gigliotti posted a testimony. Pretty strong credentials, I've seen that guy on the track and he's pretty tough on equipment.

 

liberty

 

strong as in "im going to run single digit times and never want to mess with it" strong.


or strong as in: "something reasonably affordable that has overdrive and will still not break in my car unless something goes horribly wrong... and then its cheap to rebuild."



for the first one, goto the above mentioned straight cut racing trannys.

for the 2nd one, a GM T56 is a bolt in, when it breaks, rebuild it with a comparatively cheap upgrade kit (you do have to rebuild the other ones as regular maintenance anyway) and you will probably never break it again.

or get a richmond 6spd.

 

Jerico 4-speeds are capable of withstanding 1,000+ horsepower in clutch assisted versions and even more on clutchless models. They are like $5,000 to start.

Libertys are also very strong. They offer straight cut gearsets for Ford Toploaders too.

If you want cost effective consider a G-Force T5 with straight cut gears and dog ring synchros. These are good to 600+HP and 500+ lbs/ft., and bolt right into a 3rd gen. PM me if you are interested. I build them in house.

Another option would be a T56. They are rated to 450 lbs/ft. stock. G-Force also has gearsets for them that will take them to 800 lbs/ft. and 900 horsepower. I also do these. These bolt in fairly easily too. You need to convert to a 30-spline yoke though for serious power on a T56. The big output shaft conversion and the G-Force kit all run the Viper spec 30-spline shaft.

Another options would be a Tremec TK600. Good to 600 lbs/ft. Fairly easy bolt in as well.

 

Thanks. I have a T-56 now, I bought it new. But the way the car is jetted it should run in the 650+rwtq area. I'm a little concerned about how long it will last. But it seems my best option is just rebuild this one.

TKO, I'll keep you in mind.

Has someone put together a rebuild kit for the T56 that includes the viper input shaft, bearings, kevlar syncros, shims, steel forks, etc? Or do you have to piece together your rebuild?

 

When rebuilding the T56 you buy a bearing kit, which is about $149, and a synchro kit which is about $199. This gets you all the bearings, synchro rings, synchro springs, and synchro dogs. Then you have to buy a tailshaft seal, tailshaft bushing (don't waste your time they aren't available, use a powerglide bushing and hone it with a brake hone to fit your yoke), snap rings, and anything that's damaged.

The big output shaft conversion is done on an exchange basis through D&D. The cost is $799 plus a $250 core on the tailshaft housing. They use an F-body tailshaft housing bored out to accept a 30-spline yoke, so they refund your $250 once you send them a viable core.

Other strengthening options are billet steel 3/4 dogs for $99, and a steel 3/4 fork for $49.

A T56 rebuild is not for the faint of heart. There are several cleanances inside the trans that must be set to only 0.003" of an inch or so of endplay or preload. This requires a specialized tool for the countershaft extention, and precision measuring equipment. If this is not done correctly the bearings will either burn up, or beat themselves apart. I have all the tools to rebuild T56s, and have done many. I'm not trying to scare you off from rebuilding it yourself, just consider the amount of money you are going to have tied up in it. I charge $250 to rebuild/blueprint a T56, which would include the big output installation or any of the other upgrades. If you haven't done a trans like this before it's cheap insurance. If you're dead set on trying it yourself I will help you as best I can.

 

Do you know anyone who's twisted the splines on an fbody shaft or broken the intput or output shafts? I know the T56 is rated around 450tq but people run quite a bit more on them.

Not scared of the project, just concerned on overall costs. I don't mind buying the tools, I justify that by saying "if it breaks again, I can fix it".

 

you know im all for doing things yourself... but unless you plan to do several transmissions to build experiance, i wouldnt do it myself..


anyhoo, no, i dont personally know anyone whos broken the shafts or the case.. most people fug shift forks, syncros or in the case of one of my friends, break the actual gear somehow...

 

Are there any things that must be replaced if you take one apart? Besides seals or something. Like if one bearing goes, can you just replace that. Is it similar to a 5-spd in that respect?

 

Oh, are there other options that don't necessarily 'bolt' in but can be made to fit. Such as a muncie or other "old school" trannies that would put up w/ this application? Aside from fabricating a bell housing, what else works? Sorry for all the questions, I just like exploring all my options.

 

Yes, you can just replace the damaged parts. That being said, most of the time if one bearing is bad the rest need to be replaced as well. The bearings live a hard life with only ATF to cushion them. If you've got a problem with one the others aren't far behind.

Synchros wear rather quickly on the T56. The trans shifts very smoothly, but the trade off is that the synchros have a shorter life than an old brass synchro trass.

Yes, people do break output shafts. The trans is rated to 450 lbs/ft stock, and people do get away with running more through them. The key is how they run the power through. If you are going to run slicks and have a tuned suspension that will hook the car at the track and plan to run good 60ft times making 450+ lbs/ft. it's only a matter of time before you break something. The weak link in the T56 is the output shaft, as it is only 27 spline. Even the TK500/TK600 Tremecs are 30-spline and they are rated at 500 lbs/ft and 600 lbs/ft. respectively.

If the car is a street car that will never see slicks you could probably run 700 HP through a T56 without problems. The tires will break loose before you can shock the trans enough to break it.

The question is how much of a safey margin do you want?

In truth, the T56 is going to be on par cost wise with any other option that will take this kind of abuse. A Tremec TR600 is an option, but consider what that costs. A Jerico would be sweet, but prices start at over $4,000.

"Old School" trannys are best left in the old school. Muncies were great in the 60s, 70s, and even the 80s. Technology has improved now to where Tremecs and T56s are stronger, lighter, and use readily available parts. The cost of core Muncies is obscene, and most require new gears, which are even more expensive. The musclecar boom has made parts and core prices skyrocket. Yes, you can buy brand new Muncies now made completely of aftermarket parts, but the cost is on par with a brand new TR600 and it still only has 4 gears with no overdrive. Trust me, you are better off with your T56, and I'm saying that as a guy that grew up with musclecars and M22 Muncies. The first trans I ever rebuilt was an M22. It was also the second, third, fourth, and fifth trans I rebuilt (same trans). They were good for high powered street cars, but slicks and a big block would blow them to bits (my Dad's '69 SS396 Chevell with an LS6 454). Finally we swapped the Chevell to a TH400 and never had another problem with the trans. I hated to admit defeat like that, but I also hated reeking of gear oil all the time!

 

Do the dogs cause a problem? Are the billet ones for strength or longer wear?

I was looking for something like this ^

My car dead hooked on motor (6000rpm dump) w/ a 11.5" tire in a 3400# car. The motor should put out 450-460hp at the crank w/ an additional 300 on top of that. The motor passes I'm not worried about, but the huge amount of TQ that n2o generates has me wondering already about the longetivity of my gear box.

BTW - thanks to everyone, you have all been a great help.

EDIT - hp # are at the crank.

 

lol, if you're dead hooking, i donno if the clutch can take that much spray out of the hole...

you're pretty much in "rebuild it every season or try to sqeek two out of it" territory if you dead hook with the nitrous... spray it a few feet out, and you're fine.
honestly, once you start spraying a 300 shot out of the hole, you're in auto only territory anyway..

 

The billet dogs are for strength. T56s have a 3/4 synchro assembly that is a little weaker than the 1/2. That's why the steel 3/4 fork is so popular. The stock stamped dogs can break under load, and lock the trans in 3rd or 4th gear. Not a lot of fun.

With that much power on N20 you need to get serious. If you use a stagged system it would be better. A 300HP hit all at once is a lot for the motor, trans, and rear to take.

I think your best bet with that kind of power are the G-Force gears and big output conversion, which will also convert it to triple cone (Vette spec) synchros. He's right too. You would want to tear it down every season and check the bearings, gears, etc. You'll be doing that with the motor too and probably re-ringing it, align honing, cutting the decks, etc.

A Jerico 4-Speed could easily take that kind of power without problems.

Auto wise a 700R4 is going to die under that kind of abuse, even if built properly. Likewise for a TH350. You'd be looking at a PG, TH400, or 4L80E.

 

The 300 is on a progressive controller and I can start it off from 0-8 sec ramp in, and start anywhere from 20-100%. So the 'hit' won't be quite that bad. But being a manual that's a lot of shock loading and unloading.

The clutch is a T-5 spec stage 5 (10.5" disc) rated at 1000 lbs tq. I guess I'll find out.

The motor was built to respectable on motor and put up w/ an assload of juice. Later on I want to pull it apart, re-ring and bearing it, then spray more. The kit alone will go to 600hp.

TKO, you have a PM about the G-force.

 

i had a tko II for 4 years, probably has 600 passes on it with slicks (1.6 short times)

never made a peep.....plus about 15,000 miles or so of street driving

now i have a tremec 600.....mainly for the better 1st gear