Daez

Hi, I am building my car as an LS1 with a large cam(ms4, or trex), with a 150 shot. This will be primarily a street car. I wont actually race this car much, but when I do, I would like nice results(roll racing). I've looked up info on the m12 and it seems like a good option, but it also seems like it might hamper my roll racing compared to the normal t56.

I will typically be doing around a 60 roll. is that 3/4 gap going to hurt me alot? What would be the best gear ratio to go with in the rear if I use the m12?

PewterScreaminMach

iTrader: (7)

Do not go with an MN12 for your setup. I've had one for the past year and a half and if you're going to be mostly street/roll racing, the 3/4 gap will hurt you. It helps get you off the line quick if you can hook because of the short 1st gear, but second is almost non-existent and it tends to hurt your traction quite a bit if you're running 4.10s, as well. I don't recommend it unless you're going to be tracking the car a lot or doing mostly dig runs with some VERY sticky tires.

I do mostly street driving and roll racing and if I could swap back my gearing without losing any money on the deal, I would have done it already. It's possible it would hurt my ET at the track a little bit but I only get to the track a few times a year. I put about 10,000+ miles on my car a year, though, on the street.

BlackScreaminMachine

iTrader: (17)

I have seen the difference in gearing matter depending on where the roll starts from some of the posted videos.

A properly set up car should not have any issues with traction but with that Cam, it does not come alive until 3,700 rpm and up. But most races should start off in 2nd and by that time that gap shouldnt matter that much.

I would run the gear calculator and really see what MPH and relate it to the RPM at the moment and you can correlate it to a dyno sheet to see how far your off. Its good to get a good idea of torque multiplcation. Here is a link, its a import one but still explains the theroy.

http://www.team-integra.net/sections...?ArticleID=707

PewterScreaminMach

iTrader: (7)

A properly setup car with sticky enough tires at a prepped track or with a really good burnout, you mean. Without running a VERY sticky drag radial or DOT slicks on the street, traction will be an issue in first and possibly second with 400ish rwhp or more unless you can do a really good burnout, and on the street that's not always the case.

And also, anything above 45mph and I'm very low in third gear for a roll race. Even at 45 I get only a split second of second gear, just enough not to lose the jump. I don't even like doing a 45 roll in second and will push for a 40mph or slower roll if I can because second gear is so short. It's not mentioned as much because it's not as bad as the 3-4 gap, but there is also a 2-3 gap with this transmission that's much great than the stock gearing because second gear is so short.

When you cruise on the streets a lot, you very often get roll races on the highway from 60-70 mph, which is a good spot for third, but then you get hit with that big gap going into fourth. And if they want to run from anywhere over 75 you might as well just give them the win. Trust me, I've only had about a few hundred street races over the past two years with this car. Do a search for threads started by me in the Street Racing section and you'll get four or five pages of threads.

You guys can run all the gear calculators and do all the math you want, but I'm giving you real world advice and I'll take my first hand experience over a calculator any day of the week.

And another thing about the traction comment, my car hits consistent low 1.6 60's on 16" DOT slicks with stock 17"s on the front in a full weight street car. I'd say my suspension is setup just fine. Give me some real slicks and skinnies and I'll show you a 1.5 60' timeslip, and I don't even have shocks on the car yet.

BlackScreaminMachine

iTrader: (17)

Joe, we Know your giving your personal exp but there is nothing other then doing back to back runs with the same car and swapping out the trans to really give a true real world exp and ultimately seeing a difference given all other factors being the same.

One would think you should improve but you dont know and neither does anyone else here.

Since we are dealing with transmissions that "shouldn't" show any slippage. He can run the numbers to see where the engine RPM's run and relation to MPH and engine power (RWHP). I mean if he is not dropping off too terribly then going with a shorter ratio trans may not be that terrible.

Science is often tested in a vaccume and often doesnt take in real world factors but in this case he doesnt have either to go by.

If it is that bad joe, get that trans fixed, sell it, and go back to a stocker and race your brother. Since you both are terribly close with you having a slight edge then you should smash him if going by your example.

Again, this my opinion. A little time spent running numbers never hurts. But shouldnt be the only input you use.

*Edit*

Fbody.org is down so I cant use their calculator for an easy example but here is a PDF of a t-56

https://ls1tech.com/forums/attachmen...d-rpm-gear.pdf

when the site is back up, people can run the other trans ratios and then knowing the RPM spots on the up shifts can then figure our power difference. There are tons of dyno graphs to figure that out.

BlackScreaminMachine

iTrader: (17)

I also do want to stress is Joe is giving great information, and I beleive there will be an answer found. I im working on possibly making an Excel file to explain the diff since it is a VERY good question.

PewterScreaminMach

iTrader: (7)

I know what you're saying about running the calculators, etc, I've done it myself. But what I am getting at is that I was in the same exact situation as the OP in terms of how and where I like to drive my car and do the majority of my driving and I can say from personal experience that I would swap back if money allowed. I'm not going to get enough from this rebuilt trans to be able to buy a new stocker built to handle the kind of power this transmission is, which is the primary reason I bought a new trans in the first place.

I guess what it comes down to is the fact that not only MIGHT the dead spots cost you when racing on the street from a roll, but they also make it very awkward to choose gears and speeds to do so on, which is a big thing if the majority of your driving and racing is done on the street from a roll. The gears are very short, which gives you traction issues in first and often second if you can't do a burnout or are running sticky tires, plus you get those nasty dead spots. The gearing may be great at the track, again assuming you can hook, but it is definitely not roll-racing friendly if that's your thing.

And regarding the bolded statement you made, he DOES have real world experience to go by, MY real world experience. That's why he made a post on a forum - to get opinions of people who actually know and have that real world experience with the parts he's asking about. I gave him my first hand, real world experience as it relates to his situation, which just happens to be my situation, as well (which makes it that much more applicable). If he wasn't looking for advice and real world experience, he could have just gone straight to the calculator and made a decision based on "science in a vaccuum".

OP, take my advice as you will. It's coming from someone who had a stock-geared trans with 3.42s, 3.73s, and 4.10s for over a year, and then swapped to an MN12 for the past year and a half. I have tons of track passes on all setups and hundreds of street races from both rolls and digs, the majority of which are from various rolls. I get to the track a few times a year, mostly rentals so I get 15+ passes each time, but I do the majority of my driving on the street (I put about 12,000 miles a year on my car and it's NOT my daily driver). I've also run street tires, Nittos, and MT ET Streets. I currently run DOT ET Streets on the track (and a couple times on the street) and Nittos most of the time on the street. The Nittos are useless in first and quite often second on the street with my 400-even rwhp and crappy torque. They hook in second if you do a big burnout or get lucky with weather and the surface.

Bottom line: I would switch back my trans gearing if I could do so without taking a hit financially because of the fact that I do the majority of my driving/racing on the street and often from a roll. That's all I'm trying to say here.

BlackScreaminMachine

iTrader: (17)

This is ultimately my point.

If we datalog the car and show the time in seconds of where the car is under a load which for most races should be no more then 10 seconds.

The to do it with another car with the stock t-56, to really show how long this "dead" spot is. If using absolute numbers if the t 56 is quicker then One thousandth of a second then its techinically faster but would it ultimately impact an entire race? I do not think it would.

Thats the point I argue and there are TOO many varibles to account for and no body has enough money and free time to go "Mythbusters" on this.

If roll races were measured by lasers then you could tell if there was a true difference.

PewterScreaminMach

iTrader: (7)

BTW, you know this trans is up for sale anytime someone offers me the right price, since I know you're considering getting one... All I have to be able to do is buy a new equally built trans with the stock gearing.

BlackScreaminMachine

iTrader: (17)

I know, beleive me. I got a 2nd job 2-3 hours a night under table.

Not sure if I will just throw 4.30's in the rear and a spool, or a GTO trans that is more $$$.

I'll let yea know when I get there. I got plenty of bills to pay.

Great debate btw.

PewterScreaminMach

iTrader: (7)

I think the steeper rear gears may be the way to go. Basically, it eliminates the whole "dead spot" issue that you see with this trans but gets you up and off the line very quickly, which I assume is the reason you want the trans in the first place. It's hard to describe the awkwardness of this trans on the street but it just makes roll-racing quite frustrating because you always seem to be in a bad spot unless you can pick the mph beforehand. And I always seem to run into the dead spot mph when I'm racing something that I REALLY can't afford to have that be an issue for.

One great thing I WILL say for this trans on the street is that if you happen to be one of those people who races up into a high MPH like over 120 (which is the top of fourth for me with my 4.10s), the car pulls quite hard in fifth gear. I held off an LS3 Vette and a Porsche 911 Turbo up to 140 after pulling a bit down low and I completely expected both of them to start reeling me back in once I hit fifth. The fact that fifth is so much shorter, though, really puts the car in a much better RPM once you hit that gear.

The other Porsche Turbo I ran, though, the trans cost me the race. We were on the highway and when I pulled up next to him, he just held up his hand and counted to three at around 80mph. I had to go into fourth because third wasn't an option at that speed and I bogged to around 4000 RPM or so (don't remember exactly where it is at that speed). We punched it and he jumped out almost two cars. I stopped his pull as my RPM came up and by the top of fourth I was reeling him in SLOWLY, but I couldn't catch him before he let off. Had I had the stock gearing the trans, third would have been perfect and it would have been much better for me because I wouldn't have lost the hit.

thesource

iTrader: (60)

The lower 1st gear ratio in the GTO unit is helpful on lower powered cars or cars that are heavy . In a higher powered car or a car thats lighter , the 2.66 ratio is much more user friendly and helps with traction issues . As said above , the ratios are closer so there is not as much gap between the gears .

The biggest advantage the GTO unit has over the F body is the syncro design . You could build a unit with those syncros and the 2.66 ratio but its a custom unit and would get pricey .

Daez

Yeah, I'm thinking an original t56 sounds like a better plan for my set up. I appreciate all the advice pewterscreamin. Have you ever tried any gears other than 4.10's with that trans?

PewterScreaminMach

iTrader: (7)

No problem, man. And don't mind BSM and I, we like arguing about this transmission.

No, I haven't had any other rear gears with it, just the 4.10s. That 60 roll you mention will put you a little bit low in third with 4.10s. Not a horrible spot, but 65 is optimal, especially for that big cam you're looking at running and where it makes power. 50-60 is a total dead spot in third for me, and anything between 75-85 or so is the big dead spot in fourth. If your only reason for going with steeper gearing is to get into the powerband quicker and you plan on mostly roll racing, I'd recommend steep rear gears with the stock transmission. If you were a big fan of the track and that's where most of your future goals lay, that might change things.

02NBMWS6

iTrader: (22)

I would love to trade you tranny's! I have a Viper conversion T56

melchoir

iTrader: (4)

Dead spots will be created no matter what gearing or tranny you have. If you're doing most of your races on the street in dead zones, think about changing your rear gearing.

The difference from 3rd to 4th is 0.13 from the M12 to the MN6, really not enough to cry about. Each shift in the M12 brings you to 4500+ depending on shift rpm. While the 3-4 in the MN6 brings you to 4800. Is 300rpm is enough to spend money on? I don't think so.

Daez

I can get either one for the same price pretty much. hmm is it really only like a 300 rpm difference? Cause if it's that small, then the nicer shifting from the m12 would be nice.

PewterScreaminMach

iTrader: (7)

Do you have an MN12 transmission? I don't even know why I asked. Obviously you don't or you would realize that your statement has no real world credibility. You fail to take into account things like just how fast the gears in this trans wind out. Let me ask you a question, what RPM are you at according to the calculator I'm sure you're looking at at 50-55mph in third gear? Because I'll tell you this, my limiter is set at 7000 and you can not shift into 2nd at 50-55mph with this setup. The gear winds out so fast you nail the limiter by the time your foot hits the floor. Your other option? 3rd gear at 3800-4200 RPMs. Even with my smaller cam this really hurts me, nevermind the big-*** MS4 that the OP wants to run, which is all high RPM hp and not exactly known for its low end torque.

Like I said, if this was going in a car that gets a lot of dig runs, especially at the track, it may be totally worth it because the gap in 2-3 and 3-4 doesn't hurt you as much as the benefit of getting off the line and into your RPM quicker. But if your plans are mostly roll racing, this is most likely not the trans for you. You'll probably be better off going with steeper rear gears and leaving the gaps between your tranny gears as evened out as possible so your dead spots aren't nearly so bad for you. Until you own one and have a ton of roll races under your belt, I suppose some of you will just never understand. Run your calculators all you want.

BlackScreaminMachine

iTrader: (17)

Yea, its all good.

melchoir

iTrader: (4)

I do have an MN12 transmission, so no need to get lippy about it. I run 3.23 gears so my dead spots are COMPLETELY different to yours. My 2nd runs out to 70ish in real world as well as the calculator.

4400 35 50 73 104 141 208
4500 36 51 74 106 144 213
4600 37 53 76 109 147 217
4700 37 54 78 111 150 222
4800 38 55 79 113 153 227

I wouldn't start in 3rd for a roll unless it was 60+.

Your car should be good at 30, 40, and 60 rolls.