[nh68gto]

Trans is need now for car to be able to move under its own power, and be the unit that lives there. Lot of the final specs of tires, rear and such are all subjects to change in the future. May seem backwards to some that get down to every detail.

[70 bird]

The strongest option would be a 4l80E if you want something cheaper research and pick your poison. I went with manual transmissions on a turbo fox body and wound up putting in a turbo 400. I was tired of spending more time on my back R&R of the pos than driving the car. fwiw it was a liberty tremec.

[Sirrotica]

Originally Posted by 70 bird

The strongest option would be a 4l80E if you want something cheaper research and pick your poison. I went with manual transmissions on a turbo fox body and wound up putting in a turbo 400. I was tired of spending more time on my back R&R of the pos than driving the car. fwiw it was a liberty tremec.

The exact reason I switched years ago to automatic transmissions in favor of sticks. Until 1973 everything I owned was a manual transmission car or truck.

Even on the dirt track cars I switched to T400s. Tired of laying under my daily driver GTOs fixing the clutch, transmission or shifter, plus the whole drivetrain lived longer as far as u joints and rear axles failing.

If you want to get really tired of moving the shifter, try driving an 18 wheeler for a couple years, you'll really appreciate when you get in your daily driver and only have to select drive. When I bought my 2005 GTO I was driving an 18 for a living, the last thing I wanted when I got off work was to have to manually shift gears. Even my trucks are automatics, except the 1988 IH wrecker is a 5 speed.

I know the manly thing is to have a stick shift amongst many members here, but I've rowed enough gears through the years to have had my testosterone supply good for 100 years...................

[Formulajones]

Originally Posted by nh68gto

Trans is need now for car to be able to move under its own power, and be the unit that lives there. Lot of the final specs of tires, rear and such are all subjects to change in the future. May seem backwards to some that get down to every detail.

If you know you want the overdrive, it makes tire and rear gear choices a little easier later since you'll have some wiggle room.

Without the overdrive, you get backed into a corner and you're stuck doing what a lot of people here try to get away with and that's running a tall tire, and trying to keep the rear gear numerically low, like 3.08's or 2.73's trying to make the car more drivable longer distances. It works okay, but it's still more rpm cruising than an overdrive, even when the overdrive is used with more rear gear.

Toss an overdrive in there and choices are a little more relaxed. You can go with a 26 or 27 or even a 28 inch tire, what ever you like best, and rear gear choice is more forgiving. Your GTO, like most Pontiac muscle, probably came with 3.23's or 3.55's and that can most likely just be left alone with the overdrive trans in place.

You'll have to ask yourself how much you really want to enjoy the car. If you're like some here that are lucky to see 2000 miles a year, I'd say the overdrive is probably an expense you don't really need. I'd side with a good 400 turbo and call it done if the car is originally an auto.
If you're like me, and see 10,000+ a year, the overdrive is absolutely the way to go.

[RocktimusPryme]

If you need a transmission now I would just find a running 350 or 400 (whatever came in the car to make it easier). Can be had for a few hundred dollars and can be sold for the same thing later.

That’s more or less what I did with the idea of building an OD later. 6 years later the used TH400 and 3.08 rear are still in there and doing fine

[Dragncar]

Lots of people luv 455/strokers with 3.08s and a T400. T400s are simple,cheap and the average guy can build them (Sessions/Cliff book) And in near stock form can handle 700HP.
The older I get the more I realize most of the time simple is better.

[Schurkey]

The 200-4R needs expensive aftermarket help for it to survive; and even then the gearsets are really not sized appropriately for high-torque applications. About the same for the 700-R4.

The 400 (limited mileage usage) will be the least-expensive, easiest option. A 4L80E would be suitable for higher-mileage/highway use. Either trans is far more suitable for use with a larger-cube/torque-based engine than the lesser overdrives. Neither requires anything special for aftermarket parts beyond a "shift kit"; and a "governor kit" for the 400, or an adapter plate and perhaps a controller for the 4L80E, and to assure that the thing is in good condition.

Given typical limited use of a "Hobby Car", what you give up in terms of fuel economy and engine wear with a non-overdrive trans hardly matters when deciding between a 400 and the 4L80E. The '80E will cost more initially.

[Stuart]

Keep it civil, folks. Every discussion with 200-R4 in it doesn't have to turn into a pissing match.

[pastry_chef]

Last edited by Stuart; Today at 05:30 PM.

Owner of this need to review the state of things..

My statements were VERY civil. thank you.

Even Schurkey's comment was edited...???

[pastry_chef]

I believe this was founded by Chris Casperson,,

Has anyone communicated with him?

[GTOEARL]

I haven’t read all the responses here but here’s a thought. I have a 66 Gto With a turbo 400 Trany. Was contemplating putting in the 200 or 700 overdrive transmission. I lived in San Jose California at the time and it was gonna cost me at least four grand to have it done. I talked to many transmission experts and they told me I was crazy to get rid of the bullet proof 400 transmission. I did some research with gear vendors overdrive. They make a unit that is used behind the turbo 400 to give an overdrive and split all the gears if you want to shift manually. I installed it in my garage on jackstands. Yes I had to massage the tunnel a bit to get the unit to fit.
It wasn’t that bad and I did opt to have a new driveshaft made just in case I wanted to take the unit out and return it to stock. My motivation was as some of you guys have said, about having that extra gear for highway driving. I am very happy with what I have. I can turn the unit on or off from a switch under the dash or the extra floor dimmer switch that I use if I shift manually. It was fun at the beginning but I generally just keep it in the auto mode where it goes into overdrive at about 45 miles an hour. What’s cool about it is in overdrive at 70 miles an hour with 323 rear end gears I’m doing about 2200 RPM. As opposed to the 3000 RPMs at 69 miles an hour before. Anyway just a thought in your search to find the right fit for your car.

[z man]

Have the original 400/400 auto in my 68 GTO Running 3.08 gears and 2800 rpm at 70 mph Never really checked rpm at 80 or 90 mph but not close to redline. About 1500 miles per year

[nh68gto]

Holy moly that OD unit for the th400 is over $3k!
Yikes.


I’m still not certain on what to do.
I got a smaller diameter (Chevy) B&M converter on marketplace place. I’m not sure if trans is bad or it doesn’t like the converter.