gisqc

I am toying with a few options in my search of a "close" ratio transmission I can use for my LS based Bmw road race car. Gear spacing and final drive/top speed combination is something I'm looking at closely.

I've saw a T56-Magnum advertised with 2.29/1.60/1.21/1.00/.84/.67 ratios somewhere (only at one place don't remember where). I'd be very interested in using those first 4 gears and getting rid of the 5-6 gears.

Now I think I need the 4 gear and the cluster shaft to achieve that. I tried searching but found very little information on those specific ratios, anyone know if they are readil available like 2.66/2.97 gear sets? I'm also guessing it wouldn't work to use a 2.66 or 2.97 first gear and the 3 other from the other set? Unless you can change gears on the cluster shaft to? (No idea, never went there yet!)

What about 5th and 6th gear. Would it be as easy as not putting them back on to delete them? Or anything special needs to be done?

I'm toying with 500-600tq output plans. Would a T-56 rebuilded with the right parts (new synchros/forks etc) be able to hold that very well? I know all the tremec T-56 and rebuilds are advertised so but do they use anything specials?

I feel comfortable doing the work myself, would my best bet be to buy a used T56 (might as well use a defective one while I'm at the rebuild) and refresh the synchros and forks to while I'm at it?

Jeremy@RPMTransmissions

iTrader: (12)

Unfortunately the Magnum doesn't come in the 2.29 ratio. One person/company was advertising this but it doesn't exist. The 2.66 and 2.97 Magnums are all that are available. i would recommend focusing on those gear rations and deciding what will work for you and what rear gear ratio options you have available. All the ratios are fixed in each transmission too. You can't mix and match anything 1st-4th.

As for deleting 5th and 6th, it is not quite as easy as just not putting them in. You will need to machine the gears off of the 5th/6th bottle gear but you can leave the other gears out and just install the extension shaft. When we have done 4 speed T56 transmissions we usually weld up the 5th and 6th gear gates in patten also.

500-600ftlbs shouldn't be an issue for you. The T56 gearset it good to roughly 700ftlbs depending on the weight of the car.

I would look for the nicest T56 you can find. The money you save buying a broken transmission usually gets offset by the cost of the repairs pretty fast. Parts for these transmissions aren't cheap so don't sell yourself short buying a really badly beat unit.

Hope that answers some of your questions. Feel free to let me know if you have any more.

gisqc

Well that pretty much kills it 2.66/2.97 ratios are to far apart to be useful for me. Car weight I'm hoping 2600 race ready.. maybe 2700.

Any other options that could be used for close ratios? TKO 600 roadrace is good but I'd like to end with a 1:1 gear over a .82 for rear end ratio if possible.

garys 68

iTrader: (1)

If you want a close ratio 4 speed why not a Muncie or T10, they're also about 50lbs lighter than the T56.

Jeremy@RPMTransmissions

iTrader: (12)

I agree with Gary 68 about looking at 4 speeds. But the old Muncies and T10s can have reliability issues when run hard. You can pick up a Tex T-101A up off ebay for $1,799.00 and have any gear ratio you want. They are retired NASCAR and IMCA transmissions but they work great.

gisqc

Ok I will check for 4 speed trans but reliability is definitly something I'd like!

I will also look at those T-101A you mentionned... but how easy are they to mate to a lsx block? That's also something to consider.

garys 68

iTrader: (1)

I've done both a 10 and 26 spline input to an LS motor. Both are fairly easy and cheap.
I'm assuming you're road racing so an aluminum LS flywheel, LS1,2, or 7 clutch would be a good choice. You'll need an LS7 pilot bearing, 621 BBC bell housing, and a close ratio muncie/T10 with 26 splne input. But it can be done with a 10 spline input.
Btw, Muncies have been put behind 455 torque monster motors for a decade, so most should survive behind an LS. But the hi performance nascar derivative are probably good to 6-700 ft/lbs.

gisqc

Did not get to check prices on those already but do you have a very rough idea how much the transmission alone is worth? I've found if strong enough the muncie M22 have suitable ratios. Converting to 26 spline setup is just a shaft change I'm guessing? Price is sure a factor to... because then I would just go with the TKO... only downside is the whole setup needed to run it makes the price go up a little bit over what I would hope to spend.

gisqc

Ok I made a new find about the T-56 (off the shelf ratios!!!!) I could use the 1-2-3-4th gear from the 2.66 gear set (3rd : 1.3 4th : 1.0) and swap out 5 and 6 from the .84/.67 ratio trans. If my memory is good the 5-6 gear is swapable without affecting the first 4 right?

That would give me 1.3/1.0/.84 ratio for 3-4-5 and is pretty much the same as the TKO but its stronger, easier and probably cheaper. Now I would still like to delete 6th gear... and that's probably being crazy but how doable would it be to get rid of second gear? Not like many see this as useful but if it's cheap (as no new part involved) and doable.. why not go all the way in!

jmd

iTrader: (4)

I think you're starting to mix and match parts that don't match or don't understand how ratios calculate.

If using a 2.66 first trans. and production GM 5-6 gears, you can only take fifth from .74 to .71 or .63. Ford used separate 5-6 gears in some, which don't work on the GM production mainshafts.

The 2.29 C5 race box and the Ford 2.29 road race boxes are pricey. Both are T56, not iTR6060 based as the Magnum is. But with your power and weight, the TR6060 upgrades aren't warranted. And I don't think a ZR1 based hybrid would save you any $ in the end either.

gisqc

You are right I don't know which parts comes from which trans (mostly) and I am trying to mix match part hopefully to end up with a doable option and I try to search as much as I can while asking here. I do know how ratio works tho just trying to get the right ratios for my application in a reliable trans without breaking the bank. Like I said so far I got the TKO 600 which would be ok, other options either have to be cheaper or same price and more reliable, otherwise I might as well just use the TKO.

I just looked at this http://www.chevymania.com/tech/trans-ratios.htm and picked up the 1-4 ratio I liked with the 5-6 gear I liked. It says GM trans tho but I'm not sure how accurate it is. Educate me on one thing tho how come you can use either 2.66 or 2.97 gear set in a T56 (I'm pretty sure I saw both combos advertised on a few shop site) but couldn't use the 2.97 5-6 gear on the 2.66 set? Or I am missing something there related to what you said bout Ford/Chevy difference?

And about it being T-56 or itr6060 based I just named Magnum as it was what I saw advertised on a site with the close ratio. Not looking to use a magnum necessarely (just a regulare Ls1 T56... that would be T56 based right???)

Edit : I do find readily available T56 with optional .80/.62 overdrive with 2.66 gear set... atleast that's a step forward. 1.3/1.0/.80 could do it even tho I'm intrigued as to where that .84 come from and where could I get it! It would just be perfect.

jmd

iTrader: (4)

2.66 / .50 and 2.97 / .56 GM boxes use the same 5/6 gearsets; the difference in ratio comes from maindrive to countershaft gears. There aren't production GM parts to do 2.66 / .62. I believe sponsor TDP delves into builds that combine parts for those ratios.
Yep.

garys 68

iTrader: (1)

You can find used muncies for as little as $150, rebuilt rockcrushers are over $1k. 1st gear ratios are around 2.5 for wide and 2.20 for close ratio.
If you want something economical and bulletproof, buy a cheap used muncie for the tail and misc parts, then get a rebuild kit ($120), a "supercase" for $240, and an M22 rockcrusher gearset for $500.
Under $1k and you'll have a new 75 lb trans with the ratios you want and will hold up to 600 ft/lbs all day long.

gisqc

I will definitly look into that. The ratios are very decent (read not OPTIMAL but would be my second best option), less drivetrain loss from gears (that alone might make up for the slight diff in ratios), quite lighter than other options, cheapest vs the TKO and considering my other nice option was a bmw transmission... probably way easier!

What "misc" parts from the muncie would I really need to use after I get a "supercase" gears and rebuild kit? Would it have to be in good condition or what kind of defective would still do?

Jonathan@Tick

iTrader: (5)

The Muncie or other 4 speed may be your best option, but a 2.66 gear f-body t56 can be converted to .79 / .63 overdrives by using cobra 5th and 6th drive and driven gears along with a 30 spline shaft that we have on the shelf. This would require that you machine the tailhousing for the larger shaft however.

This probably isn't what you're looking for, just thought I'd post the info.

gisqc

It is definatly another option to consider (at this point I consider all of them), machining isn't a problem for me either. What I would definitly like to do is a 6th gear delete if using a T56 because no matter what ratio it is I know it's useless. It's all of those stuff combined that adds up that I need to weight pro/cons.

Jonathan@Tick

iTrader: (5)

I suppose you could delete 6th gear if you weld up the spot for 6th on the gate plate. 6th driven gear would have to be left in tact or machine a spacer to take its place. The drive gear could be removed at this point, but some type of retainer for the keys may be needed to be used as is used on the reverse syncro on the side of the syncro that has no gear. I'm not even sure if this would work since there would be nothing for the retainer to sit against as the reverse gear retainer sits against the 5/6 driven gear. You would probably have to make another spacer with a flange just to keep the retainer in place.

It would be a lot of extra headache to remove 5 lbs of weight IMO.

tripblackls1

iTrader: (11)

i ran a deleted 5/6 gear t56 for over a year, just left the 5/6 counter gear in place and the snap rings hold the reverse gear/assemble in place
easy as cake

edit - i welded the guide plate as well

Jonathan@Tick

iTrader: (5)

deleting 5th and 6th would be much easier than deleting 6th only... The car in my sig had 5th and 6th deleted for a while just as you said.

tripblackls1

iTrader: (11)

yep, i broke my 5/6 shift fork + more 5/6 gear carnage from what i found out to be a bad rebuild from a local shop that did a rebuild on it under factor warranty but they left out the spacer that went between the case and gear set letting it drag on the case
so after the shop screwed me i slammed it back together without 5/6 and went racing the next day