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post #1 of 16 (permalink) Old 05-06-2012, 10:31 PM Thread Starter
 
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Transmission question

Has anyone swapped out the TH400 for something with more gears? I just had the rear rebuilt. I had them add an Eaton posi and 3.55 gears. I love the low end but on the freeway the engine is really racing and everyone is passing me. I feel like I need another gear.

Can I swap out my TH400 for something with more gears so I can keep the low end and have a freeway gear? If yes, is it an easy swap out or do I have to change a lot of other components?

Thanks.
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post #2 of 16 (permalink) Old 05-06-2012, 10:47 PM
 
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The 200r4 is a good OD tranny if you don't have a ton of HP. It has a deeper 1st gear, and a nice OD gear.....Eric



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post #3 of 16 (permalink) Old 05-07-2012, 12:38 AM Thread Starter
 
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Is that a 3 speed? and Is it a direct swap? When you say a ton of HP... what do you mean? I am rather stock with a hot cam headers etc. probably under 400 somewhere.
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post #4 of 16 (permalink) Old 05-07-2012, 08:02 AM
 
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A 200r4 is a close swap. You will need to move the X-member a little. 4oo HP is fine as long as you have the tranny built for it. It is a 4 speed automatic, the gear ratios start lower (higher number) and end higher (lower number).....the 4th gear is an overdrive gear. This will give you better highway performance....the OD gear is .67 therefore with 3:55 rear gears when in OD, the final drive ratio would be 2.38. Eric



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post #5 of 16 (permalink) Old 05-07-2012, 09:20 AM
 
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the 2004r will work out good for you about 1" shorter than a 400 the mount is like 2"to the rear of the 400 your gear will work out good too i put one in my old pick up last year no problems they are somtimes hard to find good luck
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post #6 of 16 (permalink) Old 05-07-2012, 10:48 AM
 
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On this note I have 2 Questions...

1. I am building a stockish 455 for my project and I am wondering if a 200r4 would handle the torque (probably in the 500+ ft lbs range) as much as the 400ish hp I am building.

2. I have a Hurst his & hers shifter, will it become unusable with a 4 speed transmission? Will I need to get a 4 speed shifter out of something late model that will fit in my console?

As always thanks all.
Scott

2005 GTO Daily Driver
1969 Custom-S Project car

1971 GTO 455 in process of rebuild TH400 NEED A NEW REAREND!!!
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post #7 of 16 (permalink) Old 05-07-2012, 11:47 AM
 
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i am not sure on how much tourque they will handle the grand national guys keep them in their cars you could check out bowtie overdrives they are helpfull and good for advice
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post #8 of 16 (permalink) Old 05-07-2012, 12:23 PM
 
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Quote:
Originally Posted by blackplate65 View Post
i am not sure on how much tourque they will handle the grand national guys keep them in their cars you could check out bowtie overdrives they are helpfull and good for advice
I have been planning to leave the TH400 in it up till recently, but my wife LOVES this car (hey I am not complaining) and is wanting to take it to the smokey mountains and on other "trips" and this is after cruising all of Route 66 as her "break in run" when we complete the restoration.

With THAT kind of driving, I'd like to have an OD.

That said, I do not want to loose my His & Hers, I love it.

I currently have the opportunity to get good core transmissions here local, a 200r4 or a 700r4. (CHEAP)

Would either work better than the other? No matter what I was in for a TH400 rebuild so I am having whatever I get gone through. So that's no problem either way.

2005 GTO Daily Driver
1969 Custom-S Project car

1971 GTO 455 in process of rebuild TH400 NEED A NEW REAREND!!!
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post #9 of 16 (permalink) Old 05-07-2012, 01:28 PM
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Uhm...why the stiff gears? I would get rid of the 3.55's and install a 3.08 or 2.93 and enjoy the car. 3.55's are terrible for a street driven car, IMO.
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post #10 of 16 (permalink) Old 05-07-2012, 09:37 PM
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Check into a Gear Vendors overdrive unit. They bolt on in place of the stock tail shaft and will handle as much torque as you can throw at them. You'll need a shorter drive shaft, and probably will have to "massage" the tunnel for a little clearance. As a bonus you can use them to turn the TH400 into a 6-speed by engaging the overdrive between each gear.

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