Rear-end swap question...

So, I have a '66 Suburban, with the original 17.5 wheels wrapped in 8-17.5 bias-ply retreads. A bitchin' mix to be sure, but not the cool wide-white radials on 15-inch steelies I have in mind, and certainly not that streetable here in Oregon, where it pisses rain nine months a year.

They're about 31" tall, and hold 60 psi. And given the fact my original State of California Service Identification says I have a factory-posi rear end, they're gonna be downright sketchy.

When you throw in my stock 292, SM420, and 4:11s, my rig tops out around 60 mph. It'll go faster, but there's a Chevy decal on the speedo admonishing one to not sustain speeds any greater, for good reason. Obviously, I'll be needing some higher gears if I want to run smaller wheels and tires.

I'm familiar with the various gear calculators on the web. What I need to know about is the process. I'd like to keep my posi, being as I may tow a small fishing boat from time to time, and also, because it's freakin' awesome and original. Can I just swap out a ring and pinion? How difficult is that?

I'm a capable guy, though I've never delved into the third member. Is this something easily fucked up? If so, what are the consequences? Is this maybe something a shop should do? I hate the idea of taking it somewhere, but if it has to happen...

Advise away!

Thanks.

P.S. Anyone looking for some original wheels?

P.P.S Totally off-topic, but does anyone know where a '66 Suburban VIN plate lives?

 

VIN plate, open up the driver side door, look up. Riveted into the doorframe above the door. The ID plate in the driver side kick panel has no meaningful info.
Here's your next problem, look for the 60-66 Chevy truck thread, and look for the Chevy truck forum that has more info than you can begin to find here.
Good luck with a neat truck.

 

Thanks Man! I wondered if I was missing something somewhere...

 

I had a 66 suburban with no posi, and the 3.73 gears in the original 12 bolt truck rear, and "normal" 15" wheels. Also had a big block and TH400 powering it. I found a rearend from a mid 70s van in a junkyard cheap, it had 3.07 gears. I swapped the gears and differential case into my suburban housing (which is much narrower than a van), and had happy highway cruising after that. Unfortunately if you have the steep gears and a posi, you won't be able to reuse the case if you go that low on the gearing. 3.40 and lower numerical ratios use the 3 series case instead of the 4 series that you have now.

 

So, I'll need a new case, and probaby lose my posi?

 

yeah, but you might want to double check exactly what you have first....pulling the cover off the rearend is a good way to start, and taking pics so we can see it helps too. and say it's a 64, they're the same, and on topic here sort of

 

I've never been inside one of those axles, but I just put a 3.42 in my '77 10-bolt a couple months ago for the first time and it was definitely doable. Like you, I cringed at the thought of taking it into a shop. The only tools I had to buy were a pinion depth setting gauge and a tiny torque wrench from Randy's Ring and Pinion. Great place to get parts too. Good luck and enjoy! I'm sure you'll do just fine.

 

By case, I assume you mean axle-housing, or are you referring to the carrier? Again, sorry for my rookie-factor.

How's about I rock something in the 3:40 range? No case change then? Would Istill lose that posi? Probably wouldn't make make much difference with smaller tires... And what's your opinion of 3:07s with a 292?

Not that big of a deal if I lose that posi. I've got a come-along. Happy cruising's what it's all about. Hell it's fun now, though thirsty and slow. Rips off the line though.

Thanks.

Having a hard time finding the forums Patrick2965 is talking about. What a noob I am.

 

The part that the ring gear is bolted to, and which holds the side gears and spider gears in it.

They have different offsets for different gear ratios, 2.73 to 3.40 use one, 3.73 up use a different one.

 

Looks like I'll be shopping for rear end-parts.

Correct me if I'm retarded, but it appears I can find a three-series case, swap it into my housing (with new gears), and it's off to the races. Boy that almost makes it sound easy!

Thanks for your help. This place is a great. Hopefully I can be of assistance at some point.

 

good info here www.stovebolt.com

 

Pull what you have and see what it is first.

I'm not an expert on Chevy rearends but I think you may have a series 4 carrier and will need a series 3 carrier. I also believe that many muscle car guys would love to get their hands on a series 4 case with a posi unit......maybe enough that they'll trade you a series 3 with a posi even up?????

For some reason though I thought they changed in late 1964 to early '65 from the earlier (pre '64) Hodgkiss style rear (similar to a 9" in the fact that the gears pull out from the front after the axles were taken out) to the 65 and up style c-clip 10/12 bolt style. Who knows....trucks may be different than passenger cars and it is 2 in the morning.

 

You're right Curly, Chilton's agrees about the discontinued Hochkiss style. And I'll probably pull some stuff soon, though it's basically my daily driver. My truck is definitely low geared-- 31" tires all around (8-17.5s), and getting near redline at 60.

Anyone got a three series case, and really want a posi?

 

Is the truck a 1/2 ton with a 12 bolt cover and 6 lug wheels? 17.5" tires is throwing me.

 

It is. And the wheels, I'm told, are somewhat rare commercial stuff. Neat, but not what I'm after. I'll see about a photobucket account, and post up some shots later. Off work with AFLAC and a broken-arm for another week ot two.

I have time to wrench, and one arm to do it with!

 

Truck and car rears use different parts.

62 was the last of the drop out center in trucks, 63 had the 12 bolt rear. Cars made the change in 65.

 

Yep....not an expert on chevy rearends. Just pulling from the fogginess of have a '65 Biscayne hooked up to a 409. I thought there might be a difference between car/truck.

Now ask me about something medical.....according to the state of Ohio I'm supposed to be a Registered Nurse....personally I like wearing the scrubs because they are comfortable and do not scratch the paint when working on the cars

 

Huh. Chilton's is wrong. Who'd have thought...

 

If you want to swap rearends to get a better gear ratio and stay on six lug, you can do what I did several years ago. I found a salvage yard '70 Chevy 1/2 ton with A/C on the firewall and an automatic shifter on the column. My hunch was right, it had 3.08 gears. No posi. It's still going 200K miles later.
There are two panhard bar variations on those trucks. Some of the earlier trucks had a fabricated bracket on the right side axle tube with a long bar. Most of the later trucks had a stud just above and right of the inspection cover with a shorter bar.

 

How about a trans swap to an O/D trans - 700R4, 200R4 or a Gear Vendors unit? That way you get to keep your rear end. I have a built 200R4 with a lock up converter in a rod with close to 700 hp, 3.89 posi diff and 29" tall rear tires and can cruise down the Fwy at just under 2100 rpm @ 70 mph all day long. Never had a problem with the trans handling the power when I get on it either - just gets a bit sideways.

 

The chances are very good that by now, the Posi unit in your truck is worn out. The one in my '62 Suburban was.

Squirrel is right about the difference in cases for different ratios, the differences in passenger car 12-bolt and truck 12-bolt stuff (the internals don't interchange), and the differences in years (pre-'62, '63-'66).

I'll add a couple things. The drop-out center section was dropped for '63, as Squirrel said, going to the GM 12-bolt. Parts are still readily available for these rear ends.

'60-'62 Chevy trucks came with an optional Dana 44 rear end. It looks VERY similar to the 12-bolt. Count the bolts holding the cover on. Dana is 10 bolts, 12 bolt has...well, 12 bolts.

Does your truck have 6-lug wheels, or 8-lug wheels?

-Brad

 

You have a good opportunity here to swap out for a Ford nine inch unit. Say some 2.90 or 3.10 gears. Also, I would look into a turbo 400 auto. Your 292 six cyl needs all the help she can get. A 283 V-8 would be a better choice. Mikey

 

Good ideas, all. But budget, low-tech and originality are the watch-words for this project.Plus, I love the inliners. Nothing against an eight though. Just sticking to what's under the hood since it's only got 34,000 on it.

Back to the reaer-end: I'm pretty sure the posi is dead, or close to it. And given the fact I''ll occasionally haul a drift boat, I'll just pick up a hand-winch for those times when I've got an icy boat ramp to deal with.

I'm intrigued by the full swap-idea. Will the rear end of a '70-ish half-ton bolt right up? Seems like that'd be the easiest way to go. For that matter, I know where a few '60s and 'seventies C-trucks are... Maybe I can find a direct-bolt in and save myself some headaches.

Plus, I need to some softer springs. According to my paperwork (and my overall ride quality), I've got heavy-duty springs in the rear. Wouldn't mind softening her up a bit while I'm at it. They definitely look thicker that those on similar civilian trucks.

 

Is the truck on coil spring or leaf spring rear? Coil spring was the most common on Chevrolets of that age. Chevy's last year for coil spring rear suspension was '72, they had 5 lug on '71 and '72 from the factory.
On a stepside, the factory coil springs ride pretty decent. I know of guys putting car rear coils under the back of pickups, but it takes the pickup out of the truck.

 

I got a set of Eaton coils for a '62 Pick-up under the back of my '62 Suburban. 2-inch p-up lowering springs dropped the back of the Suburban about 4 inches. Stock pick-up springs dropped it about 2 inches, but the trucks sit so high it's not really noticeable. They ride very, very well, and take about 20 minutes to swap out both sides.

Mine is an old CA Forestry Service vehicle and came with a 3/4-ton radiator, 283 V8, 7-blade fan, granny 4spd and HD rear springs with Dana 44 with 3.55 gears. The rear springs might have been 45 years old, but they only rode soft with 800lbs of Quick-Crete sacks in the back. Otherwise it was a kidney killer until the Eaton springs went in.

-Brad

 

Your rig sounds real close to mine. I have a 3/4 ton radiator, and heavy ass springs too, and mine was a CA Highway Dept truck. It rides really nice on smooth roads, but it's a bit rough on bumps.

I just want to drop it, and swap out the gears so I can run some smaller tires, and cruise on the highway at a reasonable speed, and RPM.

 

Ha, I know this is really old...but I bought this '66 Burb from this guy a year ago. Finally changing out the rear end this week, it sure has been making some noise!

 

Hello everybody, I new to this site. Situation: I have a 1964 gmc short bed truck 1/2 ton. I just swap out the front end with disc brakes 5 bolt. Now i need help with rear end. I have read that 73-88 rear end are 1.5 in wider than the original. Question: will this make my 20 in wheel hit the fenders if I make this swap????

thanks