Brian Browning

Hi folks,
Look like I'm up against either rebuilding or replacing my trans next week. Its a 400 turbo. Do you guys think there is any detriment to the value of my car if I don't keep the original transmission? It's a low option 71. You don't really hear people say "wow is that the original transmission?" I don't have a $ difference yet as I'm supposed to talk to the shop owner Monday morning. What do ya'll think?

Thanks as always,
Brian

7T1vette

If the car isn't all-original and in tip-top condition, don't worry about it. You can just swap THM-400 trans units. Or, if you want to upgrade to an overdrive unit, swap the 400 for a 200-4R. It will swap out easily, with no changes required for the driveshaft or crossmember. The oil pan brackets need to be modified or changed to correct ones for that model; and you will need to add a TV cable and have it adjusted properly. But, those are things your mechanic (or you) can do.

If you don't do a lot of highway driving, just swap for another THM-400.

Paul L

Just R&R with an exchange TH400 unit. Much fewer $$s.

gcusmano74

Oh boy, think about an overdrive trans!
Pick up an extra 3 or 4 mpg on the highway, probably.
It's a crime that GM didn't install OD transmissions back in the day. So many baby boomers began buying Japanese and European cars, and never did come back to American cars. .
GM once had 50% of the US market. Now they own something like 15 or 17%. A shame.

7T1vette

Yes. But, now, the market is about 3-4 times as big as it was in the 1960's. So, GM still is making the same amount of cars as then. Unfortunately, the quality is no better.....

FireballXL5

I heard from my trans guy that the 200r4 trans were designed for 6 cylinder cars and ultimately wouldn't handle the power of my 383 stroker... So I went with the 700r4... And don't regret it at all! Was a little pricey though at just under $4k for everything built to the hilt and installed...

MakoJoe

They now make kits for a 700R4 Replacement for the console that will show the Overdrive gear on the console.

While this is not the only company doing it and there are others you can use this as a start if you choose to go that direction.

http://www.proformancepowertrain.com...ette_68-82.htm

doorgunner

You can buy a paperback transmission rebuild book for about $30 with colored pics showing each step of the rebuild. Take your time and rebuild it better than new for 1/3 the price of a remanufactured transmission.

FireballXL5

Nice find on the overdrive gear selector change! Might look into that... I'm just utilizing the 3 places on mine, and cannot manually downshift into first for now... But, don't really need it... Just floor it... It'll find first when it needs to...

Brian Browning

Thanks folks,
It is original, but not rare. While I appreciate the opinions on overdrive (opinions are what I asked for after all), that wasn't the question. I am going back with a turbo 400. I'm just trying to figure out if it will hurt the value if it's not original. This may be a stupid question, but is a trans date coded?
Thanks again,
Brian

'75

Your original trans will have part of your vin number stamped onto the case.

FireballXL5

When you said you wanted to rebuild or REPLACE your trans... I didn't realize you intended to 'stay' with the th400... My bad... Hard to convey context and intention through a typed message...

I'm fairly new to the corvette scene overall... So I dunno what 'classifies ' as keeping the car 'original'. Is it just a matter of what 'looks' right on the outside and you can change internals? Or are true purists are 'Pure' in every sense of the word?

Best of luck to ya...

Easy Mike

Yep. I bought the books, bought the rebuild kit, bought one thin wall socket, wigged up a homemade cradle to hold it, and rebuilt my original TH400. It's still under there and still running fine.