The Stovebolt Site Forums The Shop Area Engine Shop rear end switch out, HELP

I need to get some advice from someone who has actually done one so I don't have too many unforseen problems.

I have a 49 chevy 3/4 ton that I'd like to change the rear end out of. I don't want to hot rod, in fact I would like to keep the truck as original as possible.

With that said, for the life of me, I don't know why the speedometer reads as high as 80 mph, I couldn't hit 80 mph if I fell off a cliff. Any way, it's also too hard and too expensive to replace the brakes and drums, that's if I can find the parts.

So the question is what rear end can I put in my truck that will exchange easily and allow me to brake better and to find readily available parts for when needed, and would allow my truck to break the cob webs off the speedo needle, maybe cruise at 65 or 70 mph.

I would like to go with a six lug 1/2 ton setup if possible because there are so many more parts for 1/2 tons vs. 3/4 tons.

Lastly for the purists, after 56 years of this truck being kept original, should I just keep the truck the way it is. I guess what I mean is, did any of you do a rear end change out on a completely original truck only to regret it afterwards? I'd like to hear some input.

Thanks in advance,
Sam

There's tons of input on rear end swaps. Do a search witnin this forum. Independent 3rd member is a very easy swap on the 3/4 tons if you have an open rear drive shaft, and this keeps your truck virtually original. This can give you a higher top end but will not help braking-in fact you will not brake as well on compression with a taller differential.

there are 4.11 and some rare 3.73 third mebers that you can get for those axles
the brakes are not realy that much harder to get
epxt that you might have to order wheel cylinders from some old parts company (Brothers,
ChevysOfThe40s, Jim Carter,)

Sam - One option you have is to find a 47-54 1/2 ton torque tube (truck)and buy the Patricks 3.55 ring and pinion.

10 or the slightly heavier 12 bolt , Oh mid 70's chevy burbs, blazers and 4x4, all had 6 lug and parts are easy to obtain. they came in 3.08, 3.43 and 3.73:1.0 ratios. spring purches may need to be moved as well as shock attachments on the axle. It's funny now, the manufacturers are placing the shock mounts on the outside of the springs like our trucks AD's but for years they had them way inboard. GO FIGURE.
cheers

I went with an early 80's Blazer rear axle with a 3:08 ratio and positraction. Very easy swap ad retained the 1/2 ton six lug wheels. You will have to cut off the blazer spring mounts and weld on new ones. If the u-bolts are not long enough to use the AD shock mounts, you may have to fab new shock mounts.

Very easy swap, took me 8 hours other than the e-brake cables which probably took another 8 hours. This is discussed in another post.

Remember if you go this way and have a stock torque tube you will also have to change the tranmission to an open driveline type.

The 3:08 ratio is great for cruising, I can now run 65 MPH at 2200 RPM. But you do lose some acceleration and power. If I had to do it again, I would look for something in the 3:40 ratio range.

So that means it never ends! I am now in the process of finishing a GMC 302 to put in the truck.

Thanks for all of your good advice, I'll keep you folks posted on how it all turns out.

this rear end was used all the way into the '70s and jim carters has a 4.10 ring & pinion conversion for it.
robert

Why spend mega-bucks on a new 4.10 ring and pinion, when you can get a good carrier with one from a '67-'72 3/4-ton truck for $60 at the pick-n-pull??? You have to use a '63-'72 carrier for the new ring and pinions, anyway.

GMC Panel has it exactly right. If you swap to any other axle, you will have 6 lugs in the back and 8 in the front. You will have to carry two spares or a cell phone. Switching to a 1/2 ton front axle will cure that and will also get rid of those 8-hole safety rims, but then you still have the expense of the Patricks gears. Find you a good 4.10 rear carrier.
Ralph

O.K., lets open another can of worms. I'm looking for a easy switch out of the rear end to get rid of the lack of supply for 49 3/4 ton brakes and to put on something that parts are plentiful for, and as long as I'm doing this I might as well switch to six lug rims. I want to use the original hub caps which for the 3/4 ton are twice the size of the 1/2 ton hub cap because it has to fit over the protuding rear axel. I don't care for the giant hub cap.

Now after I do this, what about the front rims?
Is there any way to just replace the hub with one that will change out to a six lug pattern or do I have to change out the front axel completely. Anybody know?