Upgrading the 12-bolt Truck rearend - help?

[Truckstr]

I'm in the process of upgrading my rearend (hold the jokes please ) and would like a little input (okay, I said hold the jokes! ).

Seriously. First the background: I have the stock '67 12 bolt non-posi truck rearend equipped with 4.10 gears. I already have the 5-lug axles from Early Classics and am eagerly awaiting the arrival of the caliper brackets from glock35ipsc to mount Impala SS rear discs and Camaro calipers. My intention is to race this truck every once in a while, and MAYBE put some nitrous to it. Not a lot, no more than a 125-150 shot. More than anything, it will be street truck that I take down to the local SCCA-affiliated SOLO events, but no real competition there. I just want to see what I've set-up will do.

I have a Gear Vendors under/overdrive to install behind the tranny. The yoke for it uses the 1350-series U-joint. So, I know I'll need a new drive shaft. So, starting at the front of the rearend (rear yoke), I'll need a good strong rear yoke - preferably also using the 1350-series U-joint. But which one?

I want to install a "posi" differential. I've had my eye on the Eaton 19556-010 for 4-series. I like the fact that they're rebuildable (where Auburn's cone-drive, for instance, isn't). But I've also taken a hard look at the Detroit Locker.

So, which one? The notoriously noisy, yet virtually indestructible (and a bit more expensive) Detroit Locker or the tamer and more street oriented, but still tough Eaton unit?

Now, how about gears? I prefer 3.73s over the 4.10s that I currently have. The difference (by my calculations) on the drag strip won't be very much. Day-to-day driving, however, would be much better with the 3.73s (lower revs on the interstate by over 500 RPMs). But what brand? Richmond Gear, Yukon, what?

I'm looking for input from some of you guys that have actually used some of the parts I've mentioned, but I'll take directions to somebody that can help.

Thanks in advance,
Jeff
aka TruckSTR

[AirMale]

I have a 540cu backed by a TH400 W/gearvendors to a 12bolt with 1350 yokes. I use the EATON posi with a 4.11 gear. It is the perfect set up! Call any decent rear end shop for an Eaton and the correct yoke for that 12 bolt and you'll be set. Good luck!

[Ackattack]

I have an eaton posi in my 72 GMC....has worked great on the street and at the strip. I also upgraded to a 1350 series yoke on the rearend. I think it was a dana piece I got of ebay..but can't be for sure.

I'm also into 4 wheeling and several people I know have Detroit Lockers in their Jeeps (Mine has a ARB selectable locker btw). For jeeps the Detroit works OK on the street as the Large tires, low power have minimal effect.

For a street vehicle, especially if you're going to autocross there is no way I would want a locker. I think you'll be tearing up tires and causeing a lot of extra stress on the axles during street driving.

My vote is eaton limited slip!

[Truckstr]

Originally Posted by AirMale

I have a 540cu backed by a TH400 W/gearvendors to a 12bolt with 1350 yokes. I use the EATON posi with a 4.11 gear. It is the perfect set up! Call any decent rear end shop for an Eaton and the correct yoke for that 12 bolt and you'll be set. Good luck!

Thanks for the info. I found the Eaton unit at rearendparts.com for just under $350. Sounds good to me.

What brand of ring and pinion are you using?

Cool set-up! How do you like your GV? I can't wait to get my truck back on the road all set up with the GV.

[Truckstr]

Originally Posted by Ackattack

I have an eaton posi in my 72 GMC....has worked great on the street and at the strip. I also upgraded to a 1350 series yoke on the rearend. I think it was a dana piece I got of ebay..but can't be for sure.

I'm also into 4 wheeling and several people I know have Detroit Lockers in their Jeeps (Mine has a ARB selectable locker btw). For jeeps the Detroit works OK on the street as the Large tires, low power have minimal effect.

For a street vehicle, especially if you're going to autocross there is no way I would want a locker. I think you'll be tearing up tires and causeing a lot of extra stress on the axles during street driving.

My vote is eaton limited slip!

Looks like another vote for the Eaton unit. That's the way I've been leaning. I just felt that I could use another opinion or three.

I've heard similar comments to yours about the Detroit Locker. Tires are going to be expensive enough as it is. Don't want to go too far. As far as the axles, the new ones are thicker than a set of the 12-bolt Chevelle axles I have sitting in the corner. BUT, they still have C-clips. I don't plan on doing the C-clip eliminators, so they will still be a weak link. Maybe in the future.

[cajundragger]

Im going with an eaton but I need gears tooo

[jasonb72]

Originally Posted by Truckstr

Looks like another vote for the Eaton unit. That's the way I've been leaning. I just felt that I could use another opinion or three.

I've heard similar comments to yours about the Detroit Locker. Tires are going to be expensive enough as it is. Don't want to go too far. As far as the axles, the new ones are thicker than a set of the 12-bolt Chevelle axles I have sitting in the corner. BUT, they still have C-clips. I don't plan on doing the C-clip eliminators, so they will still be a weak link. Maybe in the future.

I took my truck 12 bolt to peyton performance and he quickly talked me out of rebuilding/upgrading the 12, he said they were weaker than the car 12 bolt, and not many vendors sold upgraded parts for it. Besides it was just gonna cost me an extra $400 dollar to have a completely bad ass 9" posi built.

[Truckstr]

Originally Posted by jasonb72

I took my truck 12 bolt to peyton performance and he quickly talked me out of rebuilding/upgrading the 12, he said they were weaker than the car 12 bolt, and not many vendors sold upgraded parts for it. Besides it was just gonna cost me an extra $400 dollar to have a completely bad ass 9" posi built.

Yeah, I'm aware that the 12-bolt truck rearend is weaker than the 12-bolt car. I believe it's the diameter of the pinion gear shaft - can't remember for sure.

I've thought about a 9" Ford rearend. I need something that's bolt-in, reasonably priced, has the right gears (3.73), "posi" and 5 on 5" bolt pattern. If I could get all of that in a 9" Ford rearend for $400 (or even a bit more), then I'd probably do it.

Is that what you have? I did a quick once over of the Peyton Performance website and didn't see what I was looking for.

If I do it, then I'll have some 12-bolt EC 5 on 5" truck axles and a set of glock35ipsc's Camaro caliper brackets for sale. Oh, well.

[jasonb72]

Originally Posted by Truckstr

Yeah, I'm aware that the 12-bolt truck rearend is weaker than the 12-bolt car. I believe it's the diameter of the pinion gear shaft - can't remember for sure.

I've thought about a 9" Ford rearend. I need something that's bolt-in, reasonably priced, has the right gears (3.73), "posi" and 5 on 5" bolt pattern. If I could get all of that in a 9" Ford rearend for $400 (or even a bit more), then I'd probably do it.

Is that what you have? I did a quick once over of the Peyton Performance website and didn't see what I was looking for.

If I do it, then I'll have some 12-bolt EC 5 on 5" truck axles and a set of glock35ipsc's Camaro caliper brackets for sale. Oh, well.

Peyton quoted me 1600 to rebuild my 12 bolt with race axles 5x5 and a detroit locker, all good parts, it't gonna run me 2k to get the HD 9" case, 35 spline race axles, trutrac locker, and a good center. I just could not take the risk of putting 1.6k in the 12 bolt if it was not going to hold up to the power I am going to put on it. I am sure it would be cheaper if you didn't need the race type parts. Give him a call tell him Jason Brooks sent you, he might cut you a deal.

[1968SWBBigBlock]

2K for the 9" - make sure it includes all of your brake hardware - if not tack on another 5-7 hundred. Make sure they include the pan hard bar mount - in my searchs for a 9" that was a common item that was overlooked and added another couple hundred. The 9" is the more bullet proof way to go but I could not justfy the difference in my pricing.
I have about 1200 in my 12bolt with an Eaton posi, richmond 4:10 gears, moser axles, studs & pinion. That included set up labor, SST brake lines, chrome rearend cover etc.

[jasonb72]

Originally Posted by 1968SWBBigBlock

2K for the 9" - make sure it includes all of your brake hardware - if not tack on another 5-7 hundred. Make sure they include the pan hard bar mount - in my searchs for a 9" that was a common item that was overlooked and added another couple hundred. The 9" is the more bullet proof way to go but I could not justfy the difference in my pricing.
I have about 1200 in my 12bolt with an Eaton posi, richmond 4:10 gears, moser axles, studs & pinion. That included set up labor, SST brake lines, chrome rearend cover etc.

I already have ECE's 4 wheel disc kit, so I am good on the brakes, Stan had some brackets made for me that would work with the ends we are going with on the 9", I am also using ECE's super track bar, so I do not need the mount anymore. You are right Peyton had a nice set of Baer's for the back for about 4-500, but I did not want to have to buy new fronts two, so I will stick with what I got.