I have a small dilema

[swtman]

I have a '67 gmc with a 305 4bbl mated to a turbo 350 and 3.73 rearend. I love the get-up-and-go with the gearing but can't drive highway speed. Here is my dilema, I would like to change the tranny to a 200-4r but not sure about moving the crossmember and especially setting up TV cable and wiring in the lock-up t/c. The other option is to change my rearend gearing to something like 3.08 but I think I have the original driveline which is like about maybe 2" in diameter (pretty small) and 2 piece and I am not sure if it would hold up to the gear change. If I was to go with 3.08 there will be more torque on the driveline then with the 3.73's ,Correct?I would miss the take-off at the lights but really am more concerned with milage and highway cruising. As it is now I can't enjoy going for a cruise on the highway. So I guess what I am asking 1) will the small driveshaft take the gear change-I do have a heavy foot sometimes!! or 2)Is it really a big deal to swap to a 200-4r and get the TV cable setup and t/c wired properly? Thanks in advance for any Info!!

[lowrollin70gmc]

A gear change or tranny change are both doable on your truck. My GMC runs 3.08s from the factory behind my 350/4 barrel/3spd and it does fine on the highway and the driveshaft has no problems holding the power. So 3.08s are possible, I'm not sure on cost, but it shouldn't be too bad.

As far as swapping trannies, I run a 700R4 in my 67 Chevelle and love the OD. The swap wasn't too bad, move the crossmember back, shorten driveshaft (I don't believe it's necessary with a 200-4R), and use a TV/lockup kit from Bowtie Overdrives. The TV cable and wiring is virtually the same for the 700/200. It wasn't necessarily the cheapest route ($200) for linkages, but it was a bolt in affair and works very well.

Ironically, my 67 runs a 700R4 and 3.08s and I love the highway, I do 75 at 2000rpm and 85-90 isn't sweating my 350 at 2400. Also, with the deep first gear of a 700R4 it acts like a T350 and 3.73s. If you really want to keep it fun, this combo is great.

[mr48chev]

Going to an overdrive trans would probably be the better part of both worlds.

Worse case senario would see you taking the truck to someone who could set up the TV cable right the first time after you had the trans in the truck and hooked up.

Moving the crossmember will call for drilling new bolt holes in the frame in the correct postiions if they don't match up. That would be tedious but not all that hard. The driveshaft would most likely call for a trip to the driveshaft or machine shop.

Unless you are in the habit of making 6000rpm slam it in gear starts or loading up 3000lbs of gravel I don't think you would have much worry about breaking the drivshaft.

[Longhorn Man]

the drive shaft is fine. if you want to swap out the rear end for a 3.07 gear, then swap it and don't even think about the shaft. Its the same one that would be in a big blovk truck or in an inline 6 truck, 4.10 gears or 3.07.
a 200 4R would be a drop in physicly, assuming you have the correct short tail shaft TH350 in it now. Move the cross member to the TH400 position (holes already there) and put your current shaft right back in. The TH cable and lock up kits are easy if you use the kits (bowtie overdrives is highly recomended) and do some reading before doing the swap. BTO has LOTS to read.
As for your set up now, unless your engine is on its last leg, there is nothing keeping you from running it 100 MPH down the freeway as it sits. Even at those speeds you wouldnt be stressing the engine/tranny/rear end at all.

[swtman]

I think maybe I will look into the tranny change. I would like the best of both worlds. Thanks guys for all the opinions!

[jim zag]

My truck has a turbo 400, 3.08 gears and 255 70 15 tires and I LOVE it!!!! Just go find a used rear and change it!!!!