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my68temp

changing trans in 1968 Tempest

Question

does anyone have any experience with putting a 700R4 into a 1968 or 1969 Pontiac Tempest. I have a Stout 355 Chevy engine i would like to put in my car and I have a 700R4 trans to go behind it. the big question i have is would I have to get a different length drive shaft? If anyone has any info it would be a great help Thanks.

OK and before anyone RAGS on me, i have a numbers matching car and i need to rebuild the Pontiac 350 and ST300 trans that are in it right now but thought it would be fun to put the Chevy in it until i can get the original engine and trans rebuilt.

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To my knowledge the 700r4 is longer than that of the th350 that would have come in the car itself. Also is the 700r4 a lockup converter? If so then painless wiring makes a kit so the torque converter will lock at cruising speeds. The cross member will have to mover back about 2-4 inches for the trans which should line up with existing holes in the frame for the manual trans for that car year. Finally you TV cable will have to be set up. There are instructions on how to do it on the internet but I always get it close then take it immediately to a transmission shop to get it right.

Good luck with the swap. If you need to donate the Chevy motor to a good home afterwords I know a good home for it.

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To my knowledge the 700r4 is longer than that of the th350 that would have come in the car itself. Also is the 700r4 a lockup converter? If so then painless wiring makes a kit so the torque converter will lock at cruising speeds. The cross member will have to mover back about 2-4 inches for the trans which should line up with existing holes in the frame for the manual trans for that car year. Finally you TV cable will have to be set up. There are instructions on how to do it on the internet but I always get it close then take it immediately to a transmission shop to get it right.

Good luck with the swap. If you need to donate the Chevy motor to a good home afterwords I know a good home for it.

Thanks for the info the trans that is in there now is the SUPER TURBINE 300 2 SPEED. I will take the measurements of it to see if it is shorter like the TH350. The 700R4 came out of a 1982 GMC suburban with the tow package and it DID have the lock up torque converter I still have it so I will use it and check into the wiring from painless thanks

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Hey, I have no helpful info when it comes to the Tempest... BUT Welcome and do you have any pictures of her? :(

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Looks great! I would love to have a good project car like that. Have fun with it and I hope you keep us updated with the progress.

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Great looking Tempest!

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Thanks for the info the trans that is in there now is the SUPER TURBINE 300 2 SPEED. I will take the measurements of it to see if it is shorter like the TH350. The 700R4 came out of a 1982 GMC suburban with the tow package and it DID have the lock up torque converter I still have it so I will use it and check into the wiring from painless thanks

I just got back from taking measurements and the 700R4 is aprox 2 inches longer than the Super Turbine 300 2 speed that is in there now

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That is a very nice looking Tempest. The only other thing I forgot was did you save your yoke from the blazer. You will either have to get your driveshaft shortened or get a different one. Since this is just a temp swap I would try and find one from a Chevelle that you can cut down and make fit the car. Also Spicer make U-joints to convert from a yoke of a different trans to a driveshaft. (ie 1430 cups and 1410 cups) they maybe hard to find but they are out there. Summit racing is the one that I have sourced from in the past.

Good luck.

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That is a very nice looking Tempest. The only other thing I forgot was did you save your yoke from the blazer. You will either have to get your driveshaft shortened or get a different one. Since this is just a temp swap I would try and find one from a Chevelle that you can cut down and make fit the car. Also Spicer make U-joints to convert from a yoke of a different trans to a driveshaft. (ie 1430 cups and 1410 cups) they maybe hard to find but they are out there. Summit racing is the one that I have sourced from in the past.

Good luck.

Yes I did save the Yoke. I guess it is a good thing too (less parts to find). Thanks again for the info. this is helping allot with things I wouldn't have thought of.

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I would also suggest that you find the shop that is going to make your driveshaft and get their measurement requirements or order form. I had a custom driveshaft made when I went from a TH350 to a TH400 on my '72 Lemans convertible and from the stock 10-bolt rear end to the Mosier 12-bolt I have now. It cost me about $300 for a new driveshaft but they do all the proper cutting and balancing before I got it.

They also told me that a steel driveshaft for the street was cheaper than aluminuim. Since I was not planning on taking the car to the dragstrip and pounding on it, I didn't need the weight savings either. Aluminuim cost between $100-200 more depending on the application and speeds being reached.

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What rear gear is in the car currently? I just ask because of the 700r4 having a deeper first than that of the 300. I hear the 3.31 gear in the 10 bolt with posi makes a nice rear end for those cars.

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Hey, I have no helpful info when it comes to the Tempest... BUT Welcome and do you have any pictures of her? :)

:lol2: :lol2: but :agreed: and :blink:

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What rear gear is in the car currently? I just ask because of the 700r4 having a deeper first than that of the 300. I hear the 3.31 gear in the 10 bolt with posi makes a nice rear end for those cars.

I am running a 3.55 in my 12-bolt. I am still kicking myself for not looking for a 200-R4 instead of the TH400. I would have liked to have the overdrive gear for all the highway driving I do with it. I choose the 3.55 as a middle of the road gearing between street and performance.

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upgrading to an overdrive... visit Bowtie Overdrives. Their online tutorials pretty much cover everything from wiring the lockup, to moving the cross member.

Depending on the power of your engine, the 200-4r may be a better choice. It's much lighter than the 700-r4, but can still be built plenty strong and it's the same length as the th350.

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