Thread: 700r4 Conversion

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First, I have a 1976 GMC C1500 2wd. My transmission is on its last legs right now. I have 3.07 gears, 29.6 inch diameter tires in my truck and am turning 3000 rpm at 65 mph instead of 2300. With the gears and tires I have I should be going 86 mph at that rpm. With gas prices the way they are, I don't like the idea of burning 86 mph worth of gas and only going 65. I think the problem is with the torque converter, though, because I am not cooking the fluid and have been running like this for many miles. Anyways, I am looking into the feasability of transplanting a 700r4. There are several questions I need to know. Will the th350 shift linkage work with the 700r4? Will the gear indicator and 4 speed detents fit in my sotck non-tilt steering column? I assume it will fit on my stock crossmember. The tail shaft yoke is different and I will need a custom driveshaft made? Can I get a drive shaft and differental yoke from another short wheel base truck that came with a 700r4 and transplant it into my own so I wont need a custom driveshaft? How much more difficult are 700r4's to rebuild than a TH350? I want to be able to do all of my own work. What kind of modifications am I going to have to make to get it to stand up to 420ft lbs of torque in a 6050 lb GVWR vehicle? I really like the idea of being able to put 3.73 gears in and turning only 1900 rpm at 65 mph. I can get a rebuildable transmission cheap. Rebuild kits don't cost too much more than similar ones for TH350s. The torque converter, drive shaft, and new ring and pinion are the parts that are going to determine whether or not I can afford this. 1500 rpm is a little low of a cruising speed for a carbureted genI small block so I will need to change the gears.

Is your 350 a long tail or short tail? The yoke should be the same. You are gonna have to find a way wire up your lock up for the lock up converter or if you have the 700 rebuilt, there are ways to convert the lock up to hydraulic from electrical. Your shifter will work but you will not have manual low. A good shift kit should be enough. The 350 and 700 are very similar internally.