KevsfastZ

iTrader: (8)

I am new to the A3 scene and have a couple of questions.
I have read through all of the FAQ’s and sticky and are quite confused.
Current mods:
Performance:
-Lid
-Ported throttle body
-QTP Longtubes
-Tru Dual exhaust running out the back
-Custom Diablo tune
-150 shot of nitrous

Suspension (100% UMI):
-Boxed LCA’s
-Relocated LCA’s
-Double adjustable Torque arm (with frame mount instead of tranny)
-Ford 9in w/ 4.11’s
-Sub frame connecters
-Comp 50/50’s in the rear
-QA1 12 way adjustable up front with 300lb springs
-Welds wrapped with 325 (28in tire)
- 3.5in aluminum DS

Car ran a best of 11.9’s @ 117 on motor full weight, have not ran it on spray yet since it was just installed.
As for near future plans for the car I plan on keeping it a nitrous car, eventually do heads, cam, etc. The car is not daily driven, but will be raced a lot on the street, therefore drivability is not an issue, along as it can hook on the street and the track.
As for my following tranny questions, looking to see what you guys would do if you were in my shoes:

- What RPM stall ( want to stick with YANK)
- Would you use a trans brake?
- Case lengths (completely lost in this part, is there a setup where I can retrain factory mounting for the crossmember?)

Anything else I did not mention you guy would do?

Thanks in advance,

Kev D

SUCK MY SS

iTrader: (14)

no front suspension?

4k stall would work well with your setup...
transbrake will be nice for the track, but kinda pointless for the street unless you can make that sucker hook...
i was able to use my factory M6 trans crossmember with my TH400 swap...all i had to do was slot the hole for the trans mount bolta bit and it lines up perfect....

DanZ28

iTrader: (5)

Ditto that!!

They make two different tailshaft lengths, the short one needs a longer DS.

KevsfastZ

iTrader: (8)

Sorry for the delay, I just came back from vacation.

The car does have front suspension, QA1 12 way adj with 300lb springs.

As for the M6 crossmember, I am using a UMI CM with torque arm mounting point, I would imagine I could do the same thing.

As I said before, it will be a track car, but will also be used for "legal" street racing often.

Kev D

KevsfastZ

iTrader: (8)

Is there any advantage between the different tailshaft lengths?

Kev D

7420NW7TH

iTrader: (8)

If you plan to bracket race foot brake classes don't allow the transbrake.

b00sted

iTrader: (7)

I'd get the brake just for the track. Wire it so the kit comes on as soon as you let off the button...It'll be sick with those 4.11 gears.

3800-4000 stall...Again, on spray it'll be sick. Make sure you tell Yank everything you can about the setup so they can build the converter right and keep it efficient.

You'll need more gear on spray with that 4.11 I think.

ChevyGoldfinger

You mean shallower gears as in 3.70 or 3.50? Depending on tire diameter, that might be true. Check it on a gear/rpm/speed calculator.
As for wiring the kit to come on as soon as he lets off the transbrake, I don't think that's a good idea because he might not be over 3000 RPMs sometime when he lets off and it is armed. Stick with the WOT switch and set things up not to come on below 3000 RPM minumum. Safer IMHO.

KevsfastZ

iTrader: (8)

I am on a 28in tire and I am not sure how the gearing is in the tranny, if it will not work, what would you guys put in?

Kev D

DanZ28

iTrader: (5)

Short one is stronger and more common. You should get a new HD DS anyway. Also, if you want the speedo, you can get a tailshaft to work off the stock PCM wiring, just need to change a few perameters in it.

ChevyGoldfinger

You're not going to be concerned with the gear ratios in the tranny except for 3rd gear. You will be in 3rd at the big end and it will be (1 to 1).
On a 28" tire, 4:11s should be okay unless you're trapping over 140 mph.
I think 142 MPH puts you at 7000 RPM with 4:11 gears on a 28" tire.

I have my calculations for my 28" tire and 3.70 gears, at 140 mph trap speed I will only be at 6216 RPM. You will have to have some idea what you will be trapping and run the numbers through a calculator.
Like this one:
http://murray.faithweb.com/formulas.htm#find_rpm

Jordan S.

iTrader: (17)

does the OP have a lock up converter? If he doesn't his numbers will be different.

ChevyGoldfinger

Not sure what you mean by OP. (not a text messager here)
Let me guess. . . other person?
As for lock up converters in the TH400 trans, I have never heard of one that locks up. Mine does not.
Educate us on why the numbers will be different at 1 to 1 in high gear. I am pretty sure you refer to the vert continuing to spin up in 3rd gear because of the unlocked vert. How would you calculate the RPM at a given trap speed accurately then?

DanZ28

iTrader: (5)

OP = Original Poster.

ChevyGoldfinger

Thanks Dan. The men with almost 3000 posts to the rescue!

DanZ28

iTrader: (5)

Only took 7 years!

ChevyGoldfinger

Yeah, you were around not long after they started this thing up.
I was around just lurking since June 2002, but didn't register until Jan. 2003, so I'm coming up on 6 years myself.
Just kind of a lurker, not much of a poster.

Jordan S.

iTrader: (17)

Yes they make them. I thought I had read somewhere you had one. I guess I must have been thinking of the wrong person.

Well I'd calculate the RPM at a certain speed using 1:1 as my ratio from the formula or a calculator. Then I'd go out in the car and go WOT, when it hits that speed record the RPM. Subtract the two and there's the converter slippage. I'd do it across the board using a variety of speeds to make sure my number was accurate across the RPM range as well and to note any changes in slippage at different ends of the band. Last time I did it the difference was neglible from those points.

pddye

iTrader: (14)

At the track last time with my 3000 stall speed converter I was about right at 125 mph at 6800 rpm on a 28" tire and 3.73 gears. I was going off the stock tach so it might not be the most accurate tho.

DanZ28

iTrader: (5)

Sounds like a fair amount of slip if that RPM is correct. Using mine as a reference, I had a 4800 stall, 4.10 gears, 28" tires and trapped 126 at 6400 RPM. I would data log a run and see what the RPM is so you get a more accurate read, don't trust that stock tach to much. You should be closer to 145+ mph at 6800 RPM with your gears and tires.