NEED ADVICE/ Recommendations on...Rear END ?

[summerj]

Hello All- Just purchased a '65 fleetside last weekend. I dont know much about the what appears to be the stock rear end in it. (The pumpkin is round like some of the other Eatons I have seen on here.

I have the opportunity to purchase a 1989 Chevy Iroc Posi rear end. ($100) Assuming its the same width, would this be an upgrade. I realize I may have to move the spring pearches but thats not a big deal to me. AM I Under ESTIMATING THis JOB? Yesterday I notice a small puddle of thick gear oil on the drive way from the current rear end.

Is this Eaton Rear End Worth Keeping? Or will the IROC Posi Be an upgrade?I will also be adding disk brakes to the front so I could find some 5 bolt rotors to match the IROC Posi Rear.

truck has a mid 70's 350 with power glide. I am looking to swap it for a 30 spline 700R4.

I am setting this truck up as a daily driver. It needs to have good brake on it as I will also be pulling a trailer.

[summerj]

Also ....Forgot to ask What gear ratio in rear end would be best for 700R4 Daily driver?
What is everyone running?

[Indian113]

I'm not a expert but I wouldn't go any higher than 3:42,I have 3:73's in my 64 and it is great with the Od trans. A lot can change with the height of your tire also

[Scot_Douglas]

FWIW, the IROC posi will be a 10 bolt with an eaton gov-lock. While I've put many miles on on one, it wasn't in a hotrod; most people online have nicknamed them the "gov-bomb".

[Greshampiglet]

I'm not sure on the fit of the IROC rear end I put a 3.54 posi in my 64 GMC (it already had leaf-springs) I have the 700R4 and a 350 crate motor with an intake and 4bbl carb I'm getting 18 to 20 mpg on the freeway, as long as I keep my foot out of the pedal

[Captainfab]

I wouldn't bother with that '89 IROC rear end. They are a weak rear end, plus they have the 5 x 4.75 wheel bolt pattern. Trucks have the 5x5 wheel bolt pattern. If you do have the Eaton HO52 under your truck, should we assume your truck is a C20? If you are wanting to convert your truck to a C10, then I would suggest looking for a '64-'87 C10 rear end. As for gears behind a 700R4, I wouldn't go any taller than 3.73's since you want to pull a trailer. Of course this all depends on how tall of a tire you plan on running. That affects your overall gear ratio.

[samuellg1977]

Originally Posted by Greshampiglet

I'm not sure on the fit of the IROC rear end I put a 3.54 posi in my 64 GMC (it already had leaf-springs) I have the 700R4 and a 350 crate motor with an intake and 4bbl carb I'm getting 18 to 20 mpg on the freeway, as long as I keep my foot out of the pedal

Greshampiglet, I have exact same set-up... And mine is also in the low 20's freeway just above idling at 75-85MPH. When the secondaries open up, she'll suck dents in the gas tank, though!!

Sam

[BR3W CITY]

In with captain on this one. The 3rd gen camaro guys try to get out of that 10 bolt rear end when they start making decent power, it really wouldn't be an upgrade. The truck 12 bolt rear is available, strong and has enough aftermarket support should you want to change gear sets. The car 12 bolt is supposedly a little stronger, but since those are much harder to find these days, its probably not worth what you'd pay.
Since you mentioned going disk in the front, just get the truck 12 bolt rear...this way your rear will be 5x5, and your front will become 5x5 (assuming you just throw the newer style gear up front)

[summerj]

OK Thanks guys for the input. I will pass on the Iroc rear..
Are the gears, seals, wheel cylinders brake shoes etc. hard to come by for this stock 65 1/2 ton rear end that I have? Maybe I will just add the brackets to it and get the monte carlo or Caprice rear disks that many on here have.

I need good stopping power since I will be hauling a 2500LB catering trailer. (It too has electric brakes) . I Need it to be good daily driver.

[Captainfab]

The truck 12 bolts were used from '63-'82 in the C10's and '63-'80 in the K10's. Parts for these are readily available at either your local auto parts store, or from some of the differential parts suppliers.

For increased braking you can certainly convert to rear discs (I have the brackets to do so) in addition to front discs, or you can upgrade to the wider 2-1//2" shoes and drums which started in about '76-'77. You will need to change the backing plates to do so.

Originally Posted by summerj

OK Thanks guys for the input. I will pass on the Iroc rear..
Are the gears, seals, wheel cylinders brake shoes etc. hard to come by for this stock 65 1/2 ton rear end that I have? Maybe I will just add the brackets to it and get the monte carlo or Caprice rear disks that many on here have.

I need good stopping power since I will be hauling a 2500LB catering trailer. (It too has electric brakes) . I Need it to be good daily driver.

[BR3W CITY]

i didn't see anything about which gears are in your current rear. If its a low set of gears, it wouldn't even be worth upgrading the brakes to find out it doesn't have enough dig to get the trailer moving.
I'll be converting my rear to disc as well, which is REALLY nice when it comes to slowing down a truck AND trailer.