Manual transmission and diff set up for drag racing

peer648

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Hi everybody
I intend to go drag racing this summer, as soon as every little problems is solved. Nearest from where I live is an 1/8 mile. I want to go on 1/4 mile but probably gonna be on 1/8 more often. Motor is built and will be around 450-500whp. I have two R154, both with diffenrent problems, and my diff is from a 87 turbo auto. Stock driveshaft.

I want to know what should I do with that to be quicker on 1/8 ? I want to stay manual, I will send one of the transmission for rebuild, with probably a kit from driftmotion Rebuilt/built. Is there something better for drag racing ? For diff I have no idea what to do, and with stock driveshaft will it hold that kind of power on street tire in the begin and semi slicks later ?
 

Nick M

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The 7MGE cars have a 4.30:1 in place of your 87 turbo diff which is 3.91:1. All 7MGE Supras have a 4.30:1.
 

black89t

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to run 1/8 mile you have to run a drag radial or slick. in the 1/8 your 60ft is even more important than in the 1/4 cause you don't have that extra track to reel in cars that trap slow but launch hard. radials tend to be better to start with they are much more stable and only have to buy two compared to a full drag pack with bias ply tires. the bias ply can launch better but good driving and radials launch well too. i run a 255/50/16 mt drag radial and have gotten some good 60fts. and thats leaving with no boost of the line. although i think i want to try the Hoosier radial.

the diff and driveshaft will be fine unless completely worn out. i actually swapped out my 3.73 for the 3.90 cause the car pulls harder in 4th and 5th. doesn't bog as easy in 2nd too.

so basically you need tires and learn to launch the car so you get a good 60ft. a line lock would be a good idea too cause holding the car back doing a brake stand with sticky ass drags tires will get your clutch hot and is harder on things without one. my clutch would slip on the launch sometimes because of how hard i had to hold the brakes on burnouts. ;)
 
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suprahero

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Our cars were never intended for an 1/8 mile race. They're just too heavy in stock form and unless you're building boost off the line with some really sticky tires, you're going to run in the high nines at about 80 something miles an hour. You're making enough power to post some good numbers, but you will definitely need some better tires. I use MT ET streets on my car and drive them everywhere. I don't drive it if it's going to rain though. They're DOT approved, but I wrecked my car two days after I painted it once, and was only going 35mph. I did a complete 360 and wiped out a cavalier while on a straight away and never punched it.
All I had locally was an 1/8 mile also. My car would run between 7.5-7.9 depending on track prep and my launch. I usually trapped around 99 mph with a full interior 91 supra and five speed.
 

peer648

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Thanks for answering guys !

Good to know that I should be good with my diff and driveshaft. For tire I think I'll go mt et streets on 17's. Does 16's be better, would it worth it ?
 
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Janch

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All I had locally was an 1/8 mile also. My car would run between 7.5-7.9 depending on track prep and my launch. I usually trapped around 99 mph with a full interior 91 supra and five speed.
you must have way more power than stock with that trap speed. my best was 75.8mph and 9.5sec. 10psi boost, auto trans, 3psi off line boost (brake boosting) and shitty tires. This year would like to see how much of a difference drag radials make with pretty much same setup.
 

black89t

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Thanks for answering guys !

Good to know that I should be good with my diff and driveshaft. For tire I think I'll go mt et streets on 17's. Does 16's be better, would it worth it ?

if you don't plan on driving far to the track on your radials id get the hoosiers. they're quite a bit lighter than the mt and the sidewalls are softer and flex more like a bias ply tire. the mt has a much thicker sidewall. my buddy in his zl1 was launching like crazy with 17" hoosiers. ideally for a drag only wheel and tire 15 or 16 are going to launch better easier with the extra side wall. not that a lower profile tire can't get a good 60ft its just a little harder and will limit your best 60ft most likely. fd wheels fit our cars perfect and are really light if you can find a pair.
 

Nick M

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you must have way more power than stock with that trap speed. my best was 75.8mph and 9.5sec.
He jacked up the radiator cap and replaced everything underneath it.