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Newbie's questions on gearing

My track experience is limited to outings with a modded 3-series with an automatic. I had a chance to take the Boss out yesterday before Steeda began their work today. To my untrained hand, the gearing feels close. I assume that benefits the car on the track allowing the driver to stay on top of the power band.

As mods increase HP to 500+, is their any benefit from looser spacing? Below are the speeds @7500 rpm for the stock trans/wheels vs the T-56 transmission at various axle ratios with 20" wheels. If I were to swap out to a T-56 transmission, would the bolded ratio ruin the car for track work?

Gear Stock |T-56 (Drag Ratio) |T-56 (Close Ratio)
@rpm 7500 |7500 7500 7500 |7500 7500 7500
@axle 3.73 |3.73 4.1 4.56 |3.73 4.1 4.56
1 44 |58 53 47 |60 55 49
2 66 |82 74 67 |90 82 73
3 95 |118 107 96 |123 112 100
4 122 |172 156 140 |160 145 131
5 161 |232 211 190 |216 196 176
6 247 |343 312 281 |319 290 261
 
Not sure about the road race issues but from a drag race and street point of view, the stock gearing is near perfect for the car.
If you change the transmission you will need to go to 4.56's to be close to what it has for gearing stock. The 4.56's will generate a lot more heat in the rear diff.
I understand the road race guys run a diff cooler on a lot of thier cars already. The 4.56's may generate too much heat for that application.

On the up side, you gain a much better transmission. The MT-82 is not what I would have chosen if I was designing the Boss.
 
My S has a T-6060 (not close ratio)with 3.73 gears, which I believe is the same as a T-56. No need to change your gears for road racing, but from what I’ve heard, the close ratio trans is the way to go.
 
IIRC the top two gears are overdrive in the T56, so are probably not going to give you good acceleration. Changing the gearing in the diff compensates some. But on the plus side, you will be shifting less. Like the old 4 spd Porsches, it is fun to be able to wind the motor out linger in each gear, but in the end it is not the fastest way around the track.

2nd is too low imo on the stock trans, I would raise it to like 72 (rough guess) because unless you shift at redline (which can be an issue with our clutch), then you drop out of the meat of the power band. Also, having them a little closer would help with corners where 3rd is a little too soft and 2nd means you are bouncing on the rev limiter unless you shift while still keeled over. That depends on your particular track and driving style, but for me it is bad on mountain roads and on both tracks I have run it at. For a track specific car, I'd shift 3rd and the rest down, but since mine is mostly street that would probably not be the way to do it. It is loud enough on the highway lol
 
Thanks. I'm basically debating two options as I want the drivetrain to be bullet proof so I can BEAT on it :)

The first option is to swap out to the t-56 with a new clutch, clutch line, drive shaft, gears, truetrac diff. This requires I make some kind of gearing change/compromise.

The second option is a bit cheaper to leave the MT-82 and upgrade the clutch line, a McLeod or RAM dual clutch & flywheel, DSS carbon fiber DS, and the truetrac diff. The second option leaves the MT-82 as the weak link but retains the factory gearing. I guess if the transmission breaks, I could have it re-built stronger.
 
How about beating on it until it breaks? Most of the issues you read about are clutch related and there haven't been many trans problems reported from owners who track their cars.
 
smittytx said:
I like the bullet proof option. What is it that makes you think you need different gears, especially if you are adding power?

Nothing really other than not having experience. I've driven motorcycles for years but it will take time at the track to develop feel for the Boss. Nothing wrong I guess with sticking with the 3.73 if I switch to the T-56 and modifying later if I need to.

To NFSBOSS's point, I've spent the last 6 years building and perfecting the plane I fly. So I've developed the habit of over-researching and ensuring everything I do is to perfection. I guess I could change this habit for car modding since the results of breaking things in action are much less disastrous :)
 
milestogo said:
Nothing wrong I guess with sticking with the 3.73 if I switch to the T-56 and modifying later if I need to.

This would be my advice. Without knowing exactly how and where you'll be using it, it's difficult to give a recommendation on the rear axle ratio.

I'm also a little curious as to why you're thinking of changing to a Truetrac. On a related note, have you seen the Wavetrac?

"Milestogo" - Robert Frost?
 
I don't think the trans is a problem...the shifter is horrible!

I'll have my MGW in for next weekend and report back.

I love the close ratios of the mt82....Maybe a little less rear gear to run more mph in 5th without the rpm.
 
VTBoss302 said:
This would be my advice. Without knowing exactly how and where you'll be using it, it's difficult to give a recommendation on the rear axle ratio.

I'm also a little curious as to why you're thinking of changing to a Truetrac. On a related note, have you seen the Wavetrac?

"Milestogo" - Robert Frost?

Yes, Robert Frost. The truetrac is because I like to drag and the stock Torsen would be shredded according to the dragsters. The Wavetrac is supposed to be very good but it's less proven at the strip. I haven't tracked but I have been to the strip many times in my old car albeit not on drag radials. No drag radials as I don't have a need to break 11.49 and all the NHRA/IRHA rules that go with it.
 
milestogo said:
Yes, Robert Frost. The truetrac is because I like to drag and the stock Torsen would be shredded according to the dragsters. The Wavetrac is supposed to be very good but it's less proven at the strip. I haven't tracked but I have been to the strip many times in my old car albeit not on drag radials. No drag radials as I don't have a need to break 11.49 and all the NHRA/IRHA rules that go with it.

Cool.

Anyhow, if you intend to take it to the strip and do decide to upgrade to a T-56, then, yeah, you will probably want at least 4:10's in the rear.

As you are probably aware, Truetracs may suffer from the same "weakness" as most other helical gear limited slips. I believe it is a torque biasing diff like the Torsen and I don't think it will hook up at the strip as well as other limited slip designs. Might be something to consider.
 
If he switches to the T56, 4.56's will give a close approximation to what he has stock and that gearing works well for the street or the strip in stock form.
 
Can you not get the T-56 in custom gear ratios? I would stick with the stock trans. An aftermarket clutch line, clutch, shifter, and solid motor mounts and it'll shift like butter.
 

Sesshomurai

Zquez said:
I have a stainless clutch line for the same reason I have stainless brake lines: low expansion.

+1. I had clutch line expansion with the stock plastic line that would cause my clutch pedal to sink and stick under super hard driving. Replace it with stainless steel fixes this particular condition.
 
darreng505 said:
+1. I had clutch line expansion with the stock plastic line that would cause my clutch pedal to sink and stick under super hard driving. Replace it with stainless steel fixes this particular condition.
It didn't fix it on mine. A couple of us have had the clutch stick to the floor with the SS clutch line. The FRPP version is for use with headers and there is no claim of any other benefit other than keeping the stock plastic line from melting.
 

Sesshomurai

NFSBOSS said:
It didn't fix it on mine. A couple of us have had the clutch stick to the floor with the SS clutch line. The FRPP version is for use with headers and there is no claim of any other benefit other than keeping the stock plastic line from melting.

Did you figure out what the cause was?

A SS clutch line will fix the particular problem of the plastic line expanding, but there could be other problems lurking there.
 

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