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T-350 or T-700



My T-350 just died and what is the groups' opinion on upgrading to a T-700? Is it really worth it or not?
trans upgrade


This is just me, but I would go with the 700R4 if it has been beefed up some to handle the 400HP. There is nothing like that over drive:D

It also depends on how you drive or what you do with the vette.

check out www.700r4.com

I believe you can still get a 700r4 for under 900 out right.
hope you get back on the road soon.
I think it would be a great edition to the mods you have already done to the car. The first gear will push you hard in the seat, and the overdrive will save some gas. The prices have come way down and the electronics are very easy to figure out and connect.

Keep us posted.

Thanks for the info. Funny thing is the tranny it self is fine and was living happly behind the new engine. The torque converter is what died. It froze up and the car had enogh power to keep running, but I when from running a 12.9 to running a 16 flat. It looks like most of the torque converter is now in the tranny.

One of the best mods to my 77 was a swap to the 700R4. The only problem was to locate the proper cross piece to support the tail shaft and shorten the driveshaft. It was really worth it to get that low, low gear. For the OD I just use a toggle switch. You would really be amazed at the performance diff.
I hate to be a stick in the mud . . . I REALLY do!!

With 400 HP, I don't trust the longevity of the 700R4. Even with the beefed up sun gears, I am suspicious of it's strength.

I know that I am going to get a lot of hot comments from this statement. However, history is the greatest teacher and history is on my side.

It is not horse power, per se, that destroys a transmission - it is torque, which is the resultant twisting force. I am not comfortable with a 700R4 running anything over around 350 lb/ft.

Just my two cents. And, like I said, I'm going to get crucified for that answer. But, I run a 400 TH which is cabable in STOCK FORM to handle your 400 HP.
You are entitled to your opinion. Especially if it is based on experience. I had an 85 vette with the auto. At one time I was pushing 350-400 hsp out of the car and the transmission gave it up. Had it rebuilt and it worked great for a few years. Went back and installed an older 350 block with a 400 crank etc. etc. and was pushing a ton of torque. The transmission failed again. Sold it to a friend of mine. He blew the trans with that engine. He then proceeded to forget about the ram air mounted in the bumper where the front tag facia went and drove through a small lake at speed during a flash flood. He had just been through it about 10 minutes before in his Fiero (side mount air intake) and was not thinking in the Vette. Needless to say it turned the rods into pretzels. He then rebuilt and beefed up that motor. Not long after he got it on the road the 700R died again.

So, maybe you are right. However, when it did work, it was awesome.
i think the 700r4 is great for crusing the highway but if you just drive around town and race you can't beat the tried and true th350 or th400. either one should handle 400hp without much of a problem. i hear the 4L60E is pretty beefy but i don't know of anyone who has put one in a c3.
69MyWay said:
The first gear will push you hard in the seat, and the overdrive will save some gas.

Like Sammy Hagar sang, "Best of both worlds!" If I ever get a second, non-original, shark I'm going with a 700R4, just my 2 cents.
If you want the most bang for your buck go with the 700R4. I put one in my 79 and love it. Make sure you have someone build one who understands their faults and fixes. I know that the worst years were 82-83 and several of the 84-85 models. I had mine built by a tranny guy who builds these things for drag cars and 4x4's. I've been running it at the track all year and still shifting hard. Plus with these you can save a buck on the torque converter. Yo don't need to spend alot on one as the stock GM units due well. I run a new stock converter for a 85 IROC which is a 2000 stock stall speed and works just as well as the B&M I had in my TH350. 700R4.com has some nice crossmembers units so you dont have to mess with the emergency cable rerouting. Shifter update is allright if you need to manually shift into 1rst or you can just use the 82 shifter and cable mount. B$M have a lock up kit I use that taps into the speedo cable and allows you to tailor the converter lock up point for your taste. Nothinh like a car kicking down when you stomp on it doing 80

79 blueshark,
I hope you don't mind allot question when i start my swap to the 700R4
sounds like you have quite the set up

Well talking with the local Tranny God, he said if it were him and knowing that I like to race the car he suggested keeping the t-350. He said in his experience the T700r4 will not live long behind my engine. He also said that if the car was stock then a t-700r4 would be a great mod to the car. So I'll probably keep the T-350. For a torque converter is TCI or B&M better?
I am the odd duck here on this one usually but,...

I like TCI products.

I run a TCI streetfighter th-350 & TCI breakaway converter behind my 350hp 350. I love the feel of the TCI trans, and the converter is on the money for my stall speed requirements. I would check out TCI's page for the recomended converter speed you need.

I have heard mixed emotions on TCI stuff, but I have never had a problem with their products, and have had a cpl bad run ins with B&M stuff.

Will the car is put away for the winter so I have awhile. Talking to the local drag racers they all have said the same thing either stay with the 350 or go to the 400, but what ever I do; do not put in the 700r4 it will just not live. Thanks for all of the advice.

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