Hello, I am having trouble deciding what transmission and rear end to put in my '76 Chevy Blazer 2WD to match up with my new 383 that I had dropped in it. The engine doesn't really give hell until about 3500 RPM. The engine was dyno'd at the flywheel 437hp at 5200 RPM and 467 lbs of torque at 4500 rpm. With the TH350 and 3.08 rear end in it now it takes one second too long to get in that powerband. So I'd just like to know what transmissions and rear ends can handle that sort of power and what might be a good match for shifts landing down in the 3500 to 4000 range. I've heard the 2004R is an easy swap with the TH350. But i don't know of it's reliability and power holding capabilities.

Use of the vehicle will be mostly desert running but I would like to have the RPMs at a decent level on the freeway. And of course a lil fun at some stoplights. If it's of any concern the tires are 33's.

Also my other concern is that I'm thinking about dropping an EFI system and a twin screw supercharger on it in a few years. So the tranny would have to be something that can be modded down the road to take an estimated 700-800 hp and 800-900 lbs of torque.

How about a 14-bolts front/rear with 4.10s. Those 33" tires will keep RPMs down. The 200-4r is a great tranny, but in stock form it won't take the power. There are several companies that modify them to take tons of abuse, at a penalty to your wallet. Certain 200-4rs will take some pretty hefty numbers; specifically ones found in the hi-po cars like the GNX, and turbo T/A. Not huge numbers, but 350-400 lb-ft of torque aren't out of the question in a lighter car. I might beef it up in your heavy truck.

The key for you is a low rear ratio to get that peaky engine up to speed faster. You might even consider 4.56 gears. With the 33s and an OD you're looking at 2200 RPMs at 70 mph. Perfect for that high-revving engine. With 4.10s you're looking at 2000 RPM which is a touch on the low side. You'll give up fuel to lugging it below an optimum cruise, and the tranny will always be hunting between 50-75 mph.

Thanks Curtis. Would it be best to look for the 14 bolts as a used rear end or purchase a new one and what vehicles would I be able to find these off of. Would it be cheaper to purchase a used 200-4R and upgrade a few things and just beef it up. Or would I be better off purchasing one from a builder? And do you know of any reputable transmission builders worth buying from? Sorry for all the questions I just really don't know much of drivetrain. Thanks for your help.

Any more thoughts?

The 1973-1987 3/4 ton and 1 ton trucks will have the 14 bolt rearend or a dana 60 depending on the year. Both rearends are strong, with the 14 bolt floating axle unit being the strongest. It is very strong but also quite large and very heavy.

Large as in I will lose ground clearance?

Yes, you'll lose an inch or so of ground clearance right under the differential, but with 33" tires you'll never notice it. I actually have a 10.5" 14-bolt under my 66 Bonneville with 27" tires and it never hits anything. http://www.curtisandkim.com/bonneville.htm for details on that swap. The 9.5" 14-bolt can be found under many 3/4 ton trucks with 6 or 8 lugs without duals. Many of the light-3/4 ton trucks (in years that used them) used the 9.5" 14-bolt which is a partial floater. It is plenty strong for your purposes, as would be an 8.5" 10-bolt or a 12-bolt. The 10.5" 14 bolt (the full-floater) was used in heavy 3/4 and 1-ton applications and comes in dually and non-dually applications. They differ only in the drums and axle shafts between dually and non. Overkill, but one of the reasons I shared this with you is because not only are they gloriously strong, they almost always come with high numeric axle ratios like 3.73, 4.10 or 4.56, and are often CHEAPER than it would cost to have new gears put in your current axles. They are also a bolt-in swap for most applications. Having someone set up ring gears isn't cheap these days. I was going to put different gears in an 8.5" 10 bolt for my friend's truck, but for the $350 per axle to have someone do it, we skipped out and bought the whole 14-bolt setup from an HD truck for $200 each, including driveshaft and a spare set of drums for the rear. Just maybe bears investigation.

Anyway... that's up to you. On the topic of 200-4rs, I know of two reputable shops that can help you. PATC and DRW. Websites:

http://www.drwtransmission.com/thm_200-4r.htm
http://www.transmissioncenter.net/200-4R.htm

BTW: Partial floater means that the axle shaft itself carries some of the load. For instance, a 10-bolt axle shaft rides inside the differential on the inboard end, but physically rides on a bearing near the outer end. The weight of the vehicle is carried on the axle shaft itself. Full-floater means that both the inside and outside of the axle do not carry any weight. In the case of the 10.5" 14 bolt, the inside is carried by the differential, and the drum rides on its own set of bearings on the outside end. The axle shaft itself bolts to the drum, but all of the weight is carried on the drum's bearings, not the skinny axle shafts.

It's got a 12 bolt under there right now. So I'll check around to see if I can get any reasonable prices on gear swaps. If no go, I'll start looking for 14 bolters with some decent gears. Thanks for the sites and for the floater info, I was wondering what that meant.