New guy here, with a trans question

[bob gervais]

Hello to all, great forums you have here!

I've recently purchased a 1983 GMC 1/2 ton 4WD pickup with the 6.2 diesel to swap into my 1987 Suburban 1/2 ton 4WD. It's currently running a tired 350/broken 700R4 combo.

When looking at the 83 donor truck, the glovebox placard stated that it had an overdrive trans, however the shift indicator only showed "PRND21". Upon further inspection under the truck, the trans pan indicates that it's a TH350 trans (square pan with a corner cut off).

I was under the assumption that the 6.2 came with either the 700R4, or TH400.

I'm assuming that the 350 was swapped in place of the 700, and whomever did the swap did a complete job, swapping in the proper gear indicator as well? Or was the 350 trans installed from the factory in some models?

Thanks in advance for any help, and thanks again for a great site!

[4x4Dreamer]

to the best of my knowledge, the 350 was never behind the 6.2. The military 6.2's had a 400, and the civvie ones a 700.
I would guess that someone did a thorough job...I just can't figure out why.

[bob gervais]

Thanks for the reply!

I assumed that someone had swapped in this TH350. I remember back in the mid to late 80's, most people hated the 700, and upon its failure, would swap in anything BUT another 700. I guess that was this truck's story....

[4x4Dreamer]

I'd think a 400 would be a much better choice than a 350...but I guess as long as he never went over 50...

[bob gervais]

According to the gentleman I bought it from, who was about 80, he used it primarily for pulling his travel trailer to a campground and back home twice a year, and plowing his driveway. He bought the truck in '84, and said that he never had any trans work done to it. So, the trans must have been swapped within the first year, or he's not being honest with me.

I'm not sure what gearing it has in it, the placard states "GQ1", which could mean anything. My Burb has 3.73's presently, but if the pickup's axles are geared taller, I'm planning on swapping those over as well.

The pickup has 106k on it, fires right up cold or hot, and runs fantastically. I drove it, and got up to about 60 MPH, and it didn't seem to be all that high in the RPM range (to a gasser guy anyway).

I'm thinking it may have 3.08 gearing, which may not work out all that badly with the TH350 in my Burb, with 33" tires.

I mainly do city driving, not much highway, so for now this combo will work.

In the fall, I'll most likely rebuild the 700 that's presently in the Burb and install it behind the diesel, or maybe go for a NV4500 swap if money allows. I'd really like to have the manual!

[4x4Dreamer]

all I can say is, if you're building a 700, don't cheap out on it. Spend some cash on the Torque converter, get the upgraded servos and a cooler.

[bob gervais]

I agree about the rebuild. The cost of that is one of the factors that makes me lean toward the 4500 swap. Of course, in the interest of time, the 700 will be easier, but in the long run the 4500 may be the better option.

The Burb presently has a huge cooler that I installed last year, and I plan on running that with the diesel/350 combo, hoping that it will make it last until I get a chance to make up my mind about what trans I'm going to install permanently.(Or at least semi-permanently, seems like projects are never really done!)