best rear diff

[lynx5653]

what rear diff is best in a 58 to get proper track width and gearing ? posi would be nice.

[mr48chev]

No perfect answer on that one.

Everyone has their own ideas on the subject.

Some will say a custom 9 inch rear from one of the purveyors of custom nine inch rears is the only way to go even though they are beyond many folks budget while others think that the second Generation Camaro rears are the hot lick and now others are wrapped around the 8.8 Ford Explorer rears.

I'd prime factors outside of budget considerations are how hard you plan to drive the rig an how much horse power you plan to run.

[Indian113]

I'll get the Popcorn!

[Coach529]

DEFINATELY need more info.

HP and Budget?

[Foot Stomper]

I'm grabbing a beer!

This little tool is going to be very useful in calculating gear ratio's.
http://www.advanced-ev.com/Calculato...ze/?ratio=3.08

[1project2many]

Ooh! Ooh! I get questions like this from time to time.

what rear diff is best in a 58 to get proper track width and gearing ?

The best rear axle is one which, through a combination of wheel flange-to-flange distance, plus wheel and tire offset and width, fits within the exterior dimensions of the body in a way that meets all applicable state and federal safety regulations. The best rear axle will properly attach to all provided suspension points (OEM or modified) and will have replaceable ring and pinion sets in a variety of ratios to allow the end user to select a final gear ratio which provides optimum performance based on the engine and transmission configuration and the desired use of the vehicle and will remain in service without overhaul for many years. The best rear axle will also have rear brakes, either disc or drum type, which will assist the front brakes in stopping the vehicle safely as well as a parking brake to prevent unintended vehicle movement while parked.

posi would be nice.

I agree. Posi would be nice.

Now if only we had some details we could narrow down the field some!

[OrrieG]

1project, were you ever in politics???? You forgot that it will be painted or plated to match the design and color theme of the vehicle.

[oilslicktg]

Here you go, it'll answer all of your questions, V8 or 6 cyl, Hourse power, Transmission automatic - 350, 400r or 4 or 5 or 6 speed manual. Daily driver, or driving Miss Daisy. Good gas mileage or don't care. Rear end mounted as original or 4 bar, etc. Now measure the ordinal rear end face plate to face plate with a tape measure, take tape measure to a pull or pick your own part junk yard and start measuring, bring tools just incase, use Chevy, unless you find a ford 8" or 9" buy it. IF you find a chevy pop off the gear cover, gear ratio are stamped on ring gear. Good luck, I hope these answers helped. Got to go get that beer and popcorn now. Also I used a 76 Camaro in my 52, as it was given to me. gear stamped 2.56, fit truck just right with 4 bar and air bags, yelp, had to build all of the brackets for the read end, didn't want leaf springs. good luck.

[1project2many]

1project, were you ever in politics????

He** no! From time to time I've got to write reports for state and federally funded vehicles. I've had to learn how to state the obvious.

You forgot that it will be painted or plated to match the design and color theme of the vehicle.

We're currently seeking additional funding...

[lynx5653]

sorry i asked!!!!!!!!!!!!!!!! thought maybe there was one that most people used. am going for stock height, possible scotts ifs. egine is an lq9 with a 4l60,or 4l80 trans, will be daily driver/work truck. stock frame if i can find one up here in maine. i have a rear out of a 4x4 79 blazer would it work or is track width to wide. i do not have original rear to get measurement from and blazer rear is in storage. what else do i need for info.

[Indian113]

Don't feel bad about asking a question. The problem is the fact that you'll get so many opinions about what is right and what is wrong. I usually just search the forum if I have a question or I read the build threads on the type of truck I'm working on. Every question I have ever had has already been done on this forum.

Hopefully you won't get discouraged and can pick the right one for your needs.

[OrrieG]

guys were feeling a little frisky. Look at these threads

http://67-72chevytrucks.com/vboard/s...d.php?t=684564
http://67-72chevytrucks.com/vboard/s...d.php?t=643087

here is a chart that lists common rear end widths, note 55-59 is 62". this is axle face to axle face. http://www.carnut.com/specs/rear.html

Note the camaro/firebirds are popular choices, later z28 and trans am's come with posi and disc brakes.

[1project2many]

sorry i asked!!!!!!!!!!!!!!!! thought maybe there was one that most people used. am going for stock height, possible scotts ifs. egine is an lq9 with a 4l60,or 4l80 trans, will be daily driver/work truck. stock frame if i can find one up here in maine. i have a rear out of a 4x4 79 blazer would it work or is track width to wide. i do not have original rear to get measurement from and blazer rear is in storage. what else do i need for info.

Well, since I'm one of the guilty ones I'll apologize right away. But there really are many different paths you can follow. And every time you think you've seen them all, someone comes up with something different.

A stock LQ9 plus OD trans would really like to be matched up to anything from 3.08 to 3.73 gears. You can pick a ratio that's higher or lower but those ratios work well with truck sized tires and they'll let you play in town and cruise on the highway. Your truck is lighter than the trucks that were home to the 6.0 so you'll have plenty of power when you need it. Unless you plan to work the truck fairly hard or do a bunch of towing, you'll probably be OK using a GM 8.5 axle like found in 73-81 Camaros and Firebirds and in some Novas as well. It was a common swap years ago and it goes with the Camaro front end. Personally I'd avoid the 7.5" or 7.625" differentials used in some of the Novas and the 82+ Camaros and Monte Carlos. The 6.0 makes enough torque to kill one. If you're going to tow heavy loads or work the truck hard I'd look at a Dana 44 axle, possibly from an International Scout or older full size Jeep truck / Wagoneer. The differential in the 8.5 GM is strong enough but the axle bearings in the Dana are larger and do a better job of supporting weight over time. Axles from GM trucks from 73+ are a bit wide to fit inside the fenders. The rear axle spring perches will need to be moved also. They can be made to work but I wouldn't choose one unless I had to.

Sorry for giving you a hard time. I'm blaming it on El Nino. If we had any snow I'd be too tired to make jokes.

[mr48chev]

OK, lets start narrowing it down.

It appears that you want to run 6 lug wheels and have a stock width rear axle.

That eliminates several popular choices.

Width eliminates the easy to get in about any gear ratio with Posi 73/87 1/2 ton 4x4 or Blazer 4x4 rear axles.

The newer Chevy Colorados have 6 bolt rear axles but I am not sure on the bolt pattern. A 4x4 rear off one of those should be the right width.
A search shows that their rear has a 6 on 5-1/2 bolt pattern.

I think there are some "company is based in Japan" trucks that have the proper 6 bolt bolt pattern but some of them may be too narrow.

Having a 9 inch Ford rear built to your specs with a 6 lug bolt pattern can be done but you are looking at serious bux to do that.

I just found this while poking around to see if the Chevy Colorado rear had the same bolt pattern http://www.crawlpedia.com/bolt_patterns.htm

axle hub but we run into the wheel won't fit the hub thing on a lot of rigs. I had a set of snow tire rims on the wife's mini van that were so tight on the hub that I had to use a sledge hammer to get them off.

[lynx5653]

found a 91 trans am posi with 2:73s is the ratio a good one not up on my gear ratios

[mr48chev]

A late 70's Trans Am rear out of a rig with over drive often had 3.73 gears but unless you have OD that is a bit low for road use.

[1project2many]

I think there are some "company is based in Japan" trucks that have the proper 6 bolt bolt pattern but some of them may be too narrow.

The 4WD axles with the right bolt pattern from the trucks with IFS (85 and newer) are close enough to the right width. Most of those axles are non-posi and gear ratios are commonly 3.90, 4.10, and 4.56. In order to switch my 94 "made in Japan" truck to 3.73 gears I had to find a rear differential from a previous generation solid axle truck, roughly '79 vintage. In order to go any lower numerically would likely require some searching for a differential from a passenger car from the '70s or would require locating an aftermarket R&P which can be tough to find.

Camaros and Firebirds could be had with 3.08, 3.23, 3.42, and 3.73 gears. Posi's were always an option and many cars were equipped with posi even though they didn't have a performance package. Posi's from any of those old cars are likely in need of a reconditioning after this many years. One consideration is that a posi for a 2.56 or numerically lower gear ratio will not attach to stock 2.73 and numerically higher gears without aftermarket parts to help. Those posi's are often available cheap but I'd go with the 2.73 and up unit.

[oilslicktg]

Sorry Guy, had no idea that you were building a 4x4 until I saw your build thread and let me say what you have done to that truck is Bad A$$, sorry for being a Prick head to you. Keep up the good work.

[OrrieG]

I did not realize it was 4wd either. What are you using for front axle ratio and transfer case? You will need to have the ratios match. I used 74 K10 (Dana 44 I think)with 3.73 ration on stock 59 springs on mine. Both are open and I have never had any problems off road in snow or mud. A little wider than 59 axles but with the stock steel 16 wheels and skinny tire they are still tucked under the fenders (see avatar). Any wider rim or tire and they stick up kickup up rocks and mud on the body. They are front disc, rear drum.

[Foot Stomper]

Originally Posted by lynx5653

have a rear out of a 4x4 79 blazer would it work or is track width to wide. i do not have original rear to get measurement from and blazer rear is in storage. what else do i need for info.

Just chiming in but why wouldn't the Blazer diffy work?

[1project2many]

I wouldn't say it won't work. It's wider and the spring perches are in the wrong locations.

[oilslicktg]

Originally Posted by lynx5653

found a 91 trans am posi with 2:73s is the ratio a good one not up on my gear ratios

Lynx5653, I built a 34 ford coupe some years back, used a maverick rear 8" , I found it in the junk yard, it was just the right width, got home found the gear ration at 2.79 so I used it, I used a 4 speed to comp for the gear, runs like a bat out of hell on the freeway's but more like Fred Flintstone when I leave from a red light. What I'm saying is don't use that 2.73 gear, with an OD, but then gears can be changed and as someone stated, in a 4x4 the front & rear gears must match in ratios. Good luck.

[lynx5653]

i am scrapping the 4x4 to much work involved and truck is way to high for my taste or my wifes for that matter. I have 2 options do a frame swap or buy an original frame and change front suspension and rear end. I already have a 76 frame 2wd rolling chassis just not sure what previous owner did to frame when he put my 58 body on it. all i know is it wasnt done right as he had to cut out part of rear cab to sit on frame. in other words i am starting from scatch and just trying to get all info i can so i dont go wasting any more time and money on this build, I would hate to say what I have in that 4x4 setup right know and dont want to get in that deep again.

Thanks to all for the info

[1project2many]

I have 2 options do a frame swap or buy an original frame and change front suspension and rear end.

I may be able to locate a 55-57 style frame in reasonable condition if you decide to go that route. It's not exactly correct for a '58 but the major portions will work.

[lynx5653]

Originally Posted by 1project2many

I may be able to locate a 55-57 style frame in reasonable condition if you decide to go that route. It's not exactly correct for a '58 but the major portions will work.

will keep that in mind and thank you .I found a 59 chassis but he wants way to much for it imo. it does have a running 235 and trans but I have no need for them.