TH400 Idea for my GTO... opinions please!
08-15-2007, 08:06 PM
#1
TH400 Idea for my GTO... opinions please! Just tossing this around... let me know your pros/cons.
I've been debating for a while going to an auto in my Goat. There's no way I can afford a built 4L80E, nor do I want to dick around with getting it in and running. It seems that luck with a built 4L65 is hit or miss. I'm making 650rwhp at the moment but I have the ability to go another 200hp higher and I don't really want to worry about a built 4L65 blowing up all the time.
SO this really only leaves me with a TH400. The 400s gears are 2.48, 1.48, 1. If I ran this tranny and changed my rear end to a 3.07 final drive, the car would still be pretty streetable. I'd like to be able to drive the car and not be turning 3000rpm while cruising. I calculated it to about 2600rpm in top gear at 65mph which I feel is a decent cruise speed. Keep in mind due to the IRS in the GTO I only have 3.07, 3.46 and 3.73 to choose from in this range.
I also figured the car would do about 65mph in 1st gear, 109mph in second, and have a top speed of about 160mph figuring 6500rpm, which is what my limiter is set to now.
Any thoughts or concerns on how the car would drive and accelerate with this combo? It seems like the gearing is a bit tall, but I think I might have enough power to overcome it. I'm not sure. It is an STS car so I know the turbo would benefit from the added load.
Only other option is a built 200R4, and those are pricey as well. I can get a TH400 built up for well under a grand.
Thanks
Adam
I've been debating for a while going to an auto in my Goat. There's no way I can afford a built 4L80E, nor do I want to dick around with getting it in and running. It seems that luck with a built 4L65 is hit or miss. I'm making 650rwhp at the moment but I have the ability to go another 200hp higher and I don't really want to worry about a built 4L65 blowing up all the time.
SO this really only leaves me with a TH400. The 400s gears are 2.48, 1.48, 1. If I ran this tranny and changed my rear end to a 3.07 final drive, the car would still be pretty streetable. I'd like to be able to drive the car and not be turning 3000rpm while cruising. I calculated it to about 2600rpm in top gear at 65mph which I feel is a decent cruise speed. Keep in mind due to the IRS in the GTO I only have 3.07, 3.46 and 3.73 to choose from in this range.
I also figured the car would do about 65mph in 1st gear, 109mph in second, and have a top speed of about 160mph figuring 6500rpm, which is what my limiter is set to now.
Any thoughts or concerns on how the car would drive and accelerate with this combo? It seems like the gearing is a bit tall, but I think I might have enough power to overcome it. I'm not sure. It is an STS car so I know the turbo would benefit from the added load.
Only other option is a built 200R4, and those are pricey as well. I can get a TH400 built up for well under a grand.
Thanks
Adam
08-15-2007, 09:14 PM
#2
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You should talk to "TrakDay" on LS1gto.com. We (non-sponser) did the TH400 swap in his GTO a while ago. His was an M6 car with a Procharger (F1) but he has since gone turbo with a solid rear axle. I never drove the car on the highway but arround town it was a blast!
08-15-2007, 09:40 PM
#3
i know the shop that did "TrakDay" black F1 procharged GTO with the TH400 conversion. it looks awesome and stock (with an aftermarket shifter). it was awesome IMO. GMRacer works for that shop. Name is Transmission Physicans in Tampa. sorry i wont post any links as they are not sponsors (yet).
Last edited by gator's 99TA; 08-15-2007 at 10:12 PM.
08-16-2007, 09:29 PM
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Just a thought but you could get a different gear set for the TH400. Instead of the stock 2.48 first and 1.48 second you could get 2.75 first and 1.57 second. That way you would have a little more *** off the line with your 3.08 rear gear and still have decent highway manners. But you are right, a turbo car will like some load.
08-17-2007, 03:41 PM
#7
HydroStream6, I highly reccomend the setup. I've got 2.75 gears, Th400, really tight converter and it's absolutely kicks ***. My main problem is traction in 1st gear though. As soon as it gets past 5psi it tends to light the tires.
It's sluggish off the line without building any boost, but building just 1-2 psi on the foot brake COMPLETELY changes the way the car leaves on the street.
This past wed I went to the track and had a horrible time getting traction due to my power level/wheel tire combo (i'm going to change my wheel/tire combo). With a blazing 1.78 60' and 4psi launch I managed a 10.64 @ 133 mph hazing the tires the first 200'. 97 degrees with a 5500' DA If you are worried about track performance I say don't worry, it's been working great for me. 80 mph = 2900 rpms on 25.6" tall nittos.
It's sluggish off the line without building any boost, but building just 1-2 psi on the foot brake COMPLETELY changes the way the car leaves on the street.
This past wed I went to the track and had a horrible time getting traction due to my power level/wheel tire combo (i'm going to change my wheel/tire combo). With a blazing 1.78 60' and 4psi launch I managed a 10.64 @ 133 mph hazing the tires the first 200'. 97 degrees with a 5500' DA If you are worried about track performance I say don't worry, it's been working great for me. 80 mph = 2900 rpms on 25.6" tall nittos.
