Recommend a place to buy a rearend

[pvienneau]

Looking to change out my original 6 lug 4:11 on a 1949 with a new read end. Does any of the manf. make a rearend to fit?

[_Ogre]

no, but...

go here http://www.chevytrucks.org/tech/ifs&rearend.htm scroll way down
pick a rearend that fits your truck and get one from a junkyard

you'll need to cut all the old mounts off and weld on new spring pads from a trailer supply
i used a 3rd gen trans am rearend that was originally coil spring mounted
in the pic i am setting the pinion angle, nothing welded yet

[mr48chev]

95% of us on here are going to do pretty close to what Ogre suggested. Study the list of donor rear axle. Pick one with the right wheel mount surface to wheel mount surface that we want plus the right gear raton and decide if we want drum or disk and start hunting the wrecking yards or searching Craigslist or other sources.

Currie, Dutchmans and or Moser will all build you a rear axle based on a 9 inch Ford rear end to your specs.. Those usually start around 1000 and go up from there.

If you get a donor rear axle and have stock rear springs Classic parts has a pair of axle seats as they call them for 19.95 that have the offset holes already drilled and are the correct width for the spring. http://www.classicparts.com/1947-54-.../#.WNRo-qK1vIU That saves a lot of guess work getting the axle located right in the wheel well.

[pvienneau]

Will a limited-slip differential 3.08:1 12 BOLT GM 1/2 TON TRUCK, FOUR SPRING STYLE, 3.08:1 POSI that CAME OUT OF mid to late '70's GM PICKUP 1/2 ton TRUCK fit?

https://maine.craigslist.org/pts/6056594902.html

[hogfarm]

I agree with Mr48chevy
I found an old 9" ford and had Dutchmans shorten housing, make new axles 3:90 posi
told bill was $1600.00
and they were very fast

[_Ogre]

Originally Posted by pvienneau

Will a limited-slip differential 3.08:1 12 BOLT GM 1/2 TON TRUCK, FOUR SPRING STYLE, 3.08:1 POSI that CAME OUT OF mid to late '70's GM PICKUP 1/2 ton TRUCK fit?

https://maine.craigslist.org/pts/6056594902.html

it is wider than what's under your truck and the spring pads would need to be moved
i'm sure you could pay a shop to do what you're asking but then the cost goes way up
i paid $175 for the rearend under my truck, it's not a truck rearend but i don't plan to load it with gravel either

[franken]

I think I'd first check if new parts are available for the existing diff, as well as measuring spring perch width, WMS, etc.

[mr48chev]

I'm pretty sure he is also doing a trans Change so that is out.

Pvienneau I forget what engine and transmission you plan to run in the truck. That might help with a suggestion on what rear to put in it.

Also what lug bolt pattern do you plan for front and rear? Life gets easier if you find a rear end with a bolt pattern that matches the front bolt pattern and pick one with a gear ratio that works with your engine and rear tire size to give you respectable highway speed and a reasonable shot at some gas mileage. That is unless you are planning a drag truck or autocross truck or have other plans rather than getting out on the open road and making some miles with a big smile on your face.

The better and more complete the info you provide is the better we can help come up with a viable option.

On six lug rears GMC had leaf springs on most trucks though the sixties and I think the change from a reasonably not so wide rear to the wider rear was between 68 and 69. The Chevs in those years had coil springs and a big old ugly bracket on the rear axle.

Those mid 70's rears along with being quite wide also have a five on five bolt pattern.

[pvienneau]

My goal is to put something in the rear of the wifes truck that would allow hiway driving. It has the original 4:11. She wants to take it to more shows further away. Sucks on the hiway these days. Has the original 3 on the tree and 6 lugs. Want to keep both.

[pvienneau]

Rear end measurements are very close if not right on for the welded spring perches on the 308 posi. Plate to plate is within 1.5 inches. The posi is set up with 6 lug chevy axles. The truck has the original tranny with 3 on the tree with tall thin tires on 16 inch rims. If I use this rearend will it work with the tranny and tires? Do you need more info? Thanks

[mr48chev]

If you change to an open drive rear axle you also have to change to an open drive transmission. Not all that difficult but you end up having to buy a transmission and driveshaft along with the rear axle. You could do that with a later three speed that works with a column shift and a mid 70's Saginaw full syncro 3 speed would be real nice (that is what is in my 48) as they shift real smooth and she can even put it in low while it is still slowly rolling up to a light.

On the six lug some of the newer Chevy Colorados have six on 5.5 lug bolt pattern You have to find the right option which is Z85 to get the closest width though. Here is a link to a gear ratio discussion by the Chevy Colorado brigade on the codes. 3.42 might be a bit high for that truck but it sure would give her a nice highway speed. http://coloradofans.com/forums/70-te...ification.html

Changing the gears in your rear axle would work too but I hear Patricks is back ordered on them and Classic parts wants around 100 bucks more for the ring and pinion.

Any way you do it you can expect to spend around 1000 before you are done unless you get a real deal on a Colorado rear axle and open drive 3 speed or get a rear axle from someone that already has had the 3.55 gears installed and just swap axle and torque tube.

[whitedog76]

The 55 and later 3 speed transmissions had different shift arms than the earlier ones. You may be able to modify, not for sure. If you are wanting to keep the 3 speed, look for a 3600 (3/4 ton) being parted out. The 54/55 trucks had an open driveline. The earlier trucks were open from the carrier bearing on to the rear diff.

The rearend you were asking about will probably work. As long as it's not more than about 65" wide. You'll have to keep your skinny wheels and tires though.

The Chevy Colorados are a good place to look, Toyota and Nissan also had 6x5.5 rearends too. The 55 to 59 trucks used to be a popular place to look too, but they are getting a little hard to find.

[mr48chev]

Swapping in a 3/4 ton rear or even center section won't do him any good as the gear ratio in those is usually lower than what his wife has now. He needs somewhere close to a 3.5 gear ratio to make her happy. Plus I have never read where someone pulled the center section out of a 3/4 ton and put it in a 1/2 ton housing and made it work or if it will even work. My guess is that it won't work and is bad advise. 3/4 ton axles are held in by the bolts on the axle flange to the hub while 1/2 ton axles are held in by C clips.

Yes the shift arms will be a challenge but not one that can't be met. As in anything else you do on these trucks when you change something you have to do some adjusting on things to get them to work the way you want them to.

[whitedog76]

I guess I wasn't real clear. I was referring to the 3 speed trans used in 3/4 ton trucks. My 54 had a 3ot. I bought a trans from a 59, only to find out they were different.

[mr48chev]

Ok, that would work. If he didn't end up rebuilding the trans. Most 3/4 tons around here have 4 speeds though.

[pvienneau]

OK, I finally ripped out the original rear end and tried the gear swap with no luck. I want to now change out the rear end and drive shaft. Get rid of the closed drive shaft for an open one. I have a 235 with a 4 speed including the granny gear. What ration for driving it on hi-way? I will look around but maybe order one online.

[Second Series]

I have the 235 with SM420 4 speed. I put a 3.73 rear from an '88 suburban, it does well. I tried a 3.55, but didn't like it. I had to start in 1st every time, so no coasting to a stop and then shifting to go. The 3.73 I start in 2nd unless I'm on an incline.

[mr48chev]

The engine will probably be happiest with a 3.3 to a 3.55 ratio. That would still be comfortable for it in stoplight to stoplight traffic and give reasonable highway speed at a comfortable rpm.

This is something that may be simpler for many of us to do than tell you how to do it and what parts to use.

You still have to consider the same things I mentioned in post 8 and 11 last year.

lug bolt pattern= is it imperative that you stay with the same 6 bolt lug pattern?

That limits the supply of viable rear axles that are the proper width. Proper width meaning right at 62 inches for stock wheels with stock back spacing.

This chart is saying that 70/76 Chevy 4x4 rear axle should work if you can find a 3.55 rear end. If you aren't going to run reverse or wide wheels you can probably get away with a slightly wider rear axle. An early 70's 4x4 6 lug rear axle with 3.55 gears should run about 200 or less in most places. http://www.quickperformance.com/Susp...nts_ep_44.html

[pvienneau]

Based on this info I would order a 1970 Chevy 4x4 3:55 rear end from one the manufacturers/re builders or find one in a scrap yard?

[pvienneau]

How about this one -> http://www.carmonkeys.com/1988-CHEVR...-Ratio-Opt-GU6

[pvienneau]

I Found a 1995 Tahoe rear end 3.42 6 lug. Just awaiting the flange to flange measurement. Has anyone used the 95 Tahoe for a AD truck? GU6

[Second Series]

In reply to your message, I was running the original '47 rear end with a '59 235 and SM420 on the highway, flat between Austin and Waco. It would max out at about 60mph with it floored and no regard to rpm. I tried a 3.55 and with the SM420 the 1st gear is not syncro, so no rolling stops. I had to come to a complete stop before proceeding or lug the engine in 2nd. I thought lugging the engine was worse than reving it up. The 3.55 was free and it had a bent axle so I was out the cost of the rear u-joint. I found a 3.73 and am able to go about 80mph, but again, I floor it. I think a faster rear end would work with a transmission with all syncro and/or an engine with more HP, V8. It's a balance between keeping up with stop and go city driving, and highway driving which can be stop and go as well...

[_Ogre]

I had to come to a complete stop before proceeding

or learn to drive a stick

you can drive a stick without using the clutch at all: start, upshift and downshift
i was on a rafting trip in west virginia with staff from tennessee on their anual outing
we had an old school bus for hauling gear, that had the throwout bearing locked up and went thru the fingers
owner/driver was bummed that he had to wait a week and spend max$$ to get it fixed
in 20 minutes i taught him to drive without a clutch thru winding mountain roads
he was so happy he refunded my money and i heard he arrived home without an issue

[pvienneau]

Found a 5 lug 72 Chevelle rearend today. Guy said it's a 3.50 ratio but the 72 Chevelle never came with a 3.50 ratio rear end. Seems I will have to sacrifice somewhere maybe go to 5 lug for more options.

[pvienneau]

Found a 1996 Tahoe rear end, 3.42, 6 lug bolt pattern 51/2 inch. Measures about 60". Has anyone used this rear end in their AD? Thanks