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Member# 3287
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2,625 Posts
I think you're talking about the older model long-tail Saginaw that was the standard Chevy box until about '66 or so. It had the non-synchro first gear. I've seen them hold up fairly well to high yield engines. The problem you are likely to find is that your 6 cylinder trans has a low first gear. Something like 2.9:1. It will wind up really fast in first gear and you don't go anywhere!
 

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Member - AMC/Rambler "guru"
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1,847 Posts
The first thing to go will be the synchro between second and third. If you don't downshift and you're careful with upshifts it will last a while. Even with pretty normal driving the synchro isn't likely to last more than 500-1000 miles. I had a similar size/design Borg-Warner T-96 made for a 135 hp six behind a much bigger 250 hp six. Drove it for 18 months that way, but the synchro went in the first two months of driving. After that it was carefully timing the shifts and/or double clutching, especially for down shifts. That's not much fun! The trans was rebuilt with new gears before it went in. I igured it would last longer that way. After about 15K miles (when I pulled it) the gears looked like they had 50-60K of wear on them.

You can run the little trans behind a V-8, but you better start looking ofr a stronger trans now. Then you'll have to make other driveline mods to fit the bigger transmission. I didn't have much choice at the time except to wait to finish the car, but I'm in the military and got orders to move just a few days after pulling the original engine for a swap! Had six months notice, but no suitable trans turned up in time and I had other things to be concerned with -- getting the engine in the car and having it ready to drive and finding a house to move to in another state a 10 hour drive away!
 

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1,971 Posts
sm318 was non synchro and really shortlength, and 4 bolt side cover and was until 69

was still in 68 in the trucks at least i know was behind the 307 and 6 cyl engines on the column shift

sm326 was the fully synch behind the bigger engines and was 3" longer than the non synchand was 7 bolt side cover

good luck
 
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