Diff question

[rich_mc]

Car is a 76 Scamp with 225. I've finished the front suspension and brake upgrade and am moving on to the rear.

Plan is to pull the 7.25 out and replace with 8.75. I looked for an 8.25 for a while bit never found one. The reason for the upgrade is:
1. To be able to put disc brakes on rear
2. Big bolt pattern
3. Longer rear to avoid the need for as much wheel spacer with modern wheels
I know the 225 doesn't NEED the 8.75, but it's what I could find.

I got a nice housing and axles from a relatively local Mopar scrapper but he didn't have any 3rd members. It's out of a B-body so a few inches longer which I needed for wheel spacing.

The scrapper guy called me a couple weeks later as he'd come across a 3rd member which was reported as a 742 case, open diff, with 2.76 gears. It turned freely in one direction, but the other direction there were some sticky spots that took a good bit more effort to turn by hand than the free spinning direction. It was only $50, so figured it was a good starting point.

Upon looking closer, I did see the ring gear has some chipped/broken teeth, so I decided to tear it apart, replace gears, and rebuild before putting in the car. It came apart much easier than expected, for once.

My questions are:
1. Is this actually an open diff? It doesn't really look like the open diff pics I've found online and looks more like the sure-grip ones?
2. Is there a way to test the diff for damage other than simply rebuilding it all and getting it in the car? I'm putting together an order to Dr Diff for the new gears/seals/bearings/etc. I'm torn on whether I should just go ahead and buy one of his sure-trac units and replace this one, or if there is a test to confirm this one is good. Again, the 225 doesn't "need" the sure-trac with its "overwhelming" power (lol), but I don't really find any new/rebuilt options for replacement open diffs anywhere- it seems everyone wants sure grip so that is what is available.

 

[jbc426]

I upgraded my '68 Barracuda's stock rear end with a complete rebuilt A-body 8 3/4 rear end I bought from Dr Diff. It came on a pallet and bolted right in complete with Dr Diff's Econo Rear Disc Brake Kit, sure grip with my choice of gears and aftermarket axles.
\
I also run a pair of passenger side 3200 lbs Super Stock Springs, properly fitted slapper bars, a rear sway bar, Koni shocks, 275/60-15 Nitto Drag Radials on an 8" wide steelie rim.

This car tips the scales at a hefty 3750 lbs with a half tank of fuel, hooks up, rides and handles better than any Mopar I've ever driven in the past 40 years. I too started out with a 225 Slanty, but have since gone the stroker 5.9 Magnum route with just under 500hp.

I'm now about to put in an 850hp Performance Injection stroked 5.9 Magnum with a Stage 2 Paxton style blower, so I hope the rear end can hold up to that little upgrade.

 

[Murray]

Setting up a new ring and pinion requires special tools. I would buy one already done.

 

[rich_mc]

I upgraded my '68 Barracuda's stock rear end with a complete rebuilt A-body 8 3/4 rear end I bought from Dr Diff. It came on a pallet and bolted right in complete with Dr Diff's Econo Rear Disc Brake Kit, sure grip with my choice of gears and aftermarket axles.
\
I also run a pair of passenger side 3200 lbs Super Stock Springs, properly fitted slapper bars, a rear sway bar, Koni shocks, 275/60-15 Nitto Drag Radials on an 8" wide steelie rim.

This car tips the scales at a hefty 3750 lbs with a half tank of fuel, hooks up, rides and handles better than any Mopar I've ever driven in the past 40 years. I too started out with a 225 Slanty, but have since gone the stroker 5.9 Magnum route with just under 500hp.

I'm now about to put in an 850hp Performance Injection stroked 5.9 Magnum with a Stage 2 Paxton style blower, so I hope the rear end can hold up to that little upgrade.

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Very nice! I'd considered just buying a whole unit but last I checked the Dr was slammed and understaffed so mostly selling parts rather than any finished units or 3rd members, hence the decision to gather parts myself and try my best (fingers crossed)... I do imagine that, like yours, mine won't always have a shortage of HP as the project progresses.

 

[Dana67Dart]

1. Is this actually an open diff? It doesn't really look like the open diff pics I've found online and looks more like the sure-grip ones

That is a clutch type sure-grip. Very rebuildable as long as not damaged internally.

I upgraded my '68 Barracuda's stock rear end with a complete rebuilt A-body 8 3/4 rear end I bought from Dr Diff. It came on a pallet and bolted right in complete with Dr Diff's Econo Rear Disc Brake Kit, sure grip with my choice of gears and aftermarket axles

Setting up a new ring and pinion requires special tools. I would buy one already done

Where is the fun in that. Nothing to learn, no new tools to buy, no pride in your accomplishments, absolutely no braggin' rights

Why doesn't he just go out and buy a resto mod!

 

[jbc426]

Nothing wrong with buying professionally set-up components for a build. Knowing when to use experts or do it yourself is a personal choice based on a lot of variables. In the end, it's the combination that matters.

 

[jbc426]

Very nice! I'd considered just buying a whole unit but last I checked the Dr was slammed and understaffed so mostly selling parts rather than any finished units or 3rd members, hence the decision to gather parts myself and try my best (fingers crossed)... I do imagine that, like yours, mine won't always have a shortage of HP as the project progresses.

The old adage that, "Speed costs money. How fast do you want to go?" is so true. I've found that this hot rodding thing is a progressive disease that gets faster with age. Dang, every vehicle I have is supped up beyond what most normal people can't even fathom.

 

[doug 371]

Nice score for 50 bucks!

 

[rich_mc]

That is a clutch type sure-grip. Very rebuildable as long as not damaged internally.






Where is the fun in that. Nothing to learn, no new tools to buy, no pride in your accomplishments, absolutely no braggin' rights

Why doesn't he just go out and buy a resto mod!

Thanks for the confirmation on it being SG. I thought that was the case but figured someone here would be more sure than I am.


And about the new tools things - you're right... I've found I've gotta buy something new every time I turn around on this project. I did get a press a while back to be able to do the rebuilds on the LCA's, so I've got that now. Of course, it's Harbor Freight which means its got a huge puddle of oil under it where the jack is leaking now, but I guess I'll fix/replace that too... I have watched a few vids and see that a dial indicator may end up being needed, so I'll cross that bridge when I get to it... I'll sometimes buy components for things complete, but for this car so far have been trying to do as much as possible by myself - not because of the cost so much (as the tools required often offset the "savings" from doing it yourself) but because I'm enjoying the process, time spent, learning, and having stuff to do in the evenings/weekends - I'm a single guy and my son's growing up, in high school now and has friends, so I'm no longer at the point that I've gotta be keeping an eye on the kid all the time. I do manage to drag him down to the garage a bit here and there. I think soon he'll want to do more in the garage as my dad plans to give him his '10 Challenger SE once he's able to start driving and he's pretty excited about that. I had an '09 R/T and then an '18 Scat Pack Challengers and the boy loved those, but sold and switched to the Scamp since I now have a company vehicle for daily driving.

 

[rich_mc]

Nice score for 50 bucks!

I'm kinda figuring that out! I thought it was a decent deal when I thought it was open diff, but being SG for $50 is way better!

 

[66fs]

I'm kinda figuring that out! I thought it was a decent deal when I thought it was open diff, but being SG for $50 is way better!

That would be a deal for a 742 case, let alone the good Sure Grip. You will need to have the spring perches move to the A Body distance.

 

[RustyRatRod]

What you scored for 50 bucks is a Dana Powerlock sure grip unit. That's the strongest 8 3/4 carrier Chrysler used.

 

[rich_mc]

That would be a deal for a 742 case, let alone the good Sure Grip. You will need to have the spring perches move to the A Body distance.

Yep - I've got a flux core welder I'll use to tack them in place, but then take the housing to the guy on the other side of town I know who can weld to where things actually stick, unlike mine...

 

[Dana67Dart]

Dont forget to have it straightened after the welding

 

[rich_mc]

What you scored for 50 bucks is a Dana Powerlock sure grip unit. That's the strongest 8 3/4 carrier Chrysler used.

Excellent!

I just ordered a bunch o' stuff and will plan to assemble it all on the bench before putting in the car to see if the sticky spots in rotation go away once I don't have chipped gears. I'll certainly avoid opening the SG unit unless proven necessary.

Thank you all for the tips - I'm sure I'll be back for more guidance once I get the parts in and get to work on it.

 

[rich_mc]

Dont forget to have it straightened after the welding

Do I get that done at the same place where I can get wires stretched and muffler bearings?

 

[66fs]

Yep - I've got a flux core welder I'll use to tack them in place, but then take the housing to the guy on the other side of town I know who can weld to where things actually stick, unlike mine...

I do the same, even if mine is a mig. I know I am not a welder.

 

[Brooks James]

If it needs spider gears good luck finding new ones for a 742 case sure grip. They are the weak link.
Original style clutches are hard to find. 9 1/4 ' s clutches will work with slight mods. Available from Dr Diff.

 

[Dana67Dart]

Do I get that done at the same place where I can get wires stretched and muffler bearings

Not a joke.

You are welding on a formed tube part and not as thick a wall as a Dana 60 etc.

I have a housing that so eone didn't heed the FSM and they tightened the u bolts too tight and crushed the tube.

I have not measured it but I am sure the housing is not streight

The heat WILL cause the metal to move.

Google it. There are photos showing how far out some housings are.



Projects - Straightening an axle housing - How straight ?

Is this 8 3/4 housing bowed?

First time straightening an 8 3/4 housing!

 

[rich_mc]

Not a joke.

You are welding on a formed tube part and not as thick a wall as a Dana 60 etc.

I have a housing that so eone didn't heed the FSM and they tightened the u bolts too tight and crushed the tube.

I have not measured it but I am sure the housing is not streight

The heat WILL cause the metal to move.

Google it. There are photos showing how far out some housings are.



Projects - Straightening an axle housing - How straight ?

Is this 8 3/4 housing bowed?

First time straightening an 8 3/4 housing!

Well I'll be damned... The guys at my old work always just welded super short sections and let it cool a lot to avoid warpage when it was important that something remain straight, but from what I was reading there it seems there is a good chance it might be crooked already... Thanks for the heads up - I'll have to do some looking/measuring... I'm only a few hours from Moser so maybe it'd make sense for me to run the housing up there so they can put the perches on in a fixture I'm sure they probably have...

 

[Dana67Dart]

I saw one on FABO IIRC where the housing was tweeked from a launch.

You did not need a tape measure to see how far it was out.

 

[Brooks James]

If it needs spider gears good luck finding new ones for a 742 case sure grip. They are the weak link.
Original style clutches are hard to find. 9 1/4 ' s clutches will work with slight mods. Available from Dr Diff. I have a set if you're interested.

 

[66fs]

... I'm only a few hours from Moser so maybe it'd make sense for me to run the housing up there so they can put the perches on in a fixture I'm sure they probably have...

That's what I would do. Then you know it would be good.

 

[jbc426]

Well I'll be damned... The guys at my old work always just welded super short sections and let it cool a lot to avoid warpage when it was important that something remain straight, but from what I was reading there it seems there is a good chance it might be crooked already... Thanks for the heads up - I'll have to do some looking/measuring... I'm only a few hours from Moser so maybe it'd make sense for me to run the housing up there so they can put the perches on in a fixture I'm sure they probably have...

I just had an 8 3/4 shortened at a rear end shop that specializes in rear ends. They used a jig that consists of a long round bar that bolts internally to the carrier and the end flanges to stabilize the housing for welding, which they weld in short sections to limit heat build up.

 

[cudamark]

If the pinion bearings are still good, there's no need for any fancy tools and/or shims to set things up. A simple dial indicator to set the backlash is simple and all you need. If the pinion bearings are bad, yeah, you need to do the full monty. If you don't want or need the sure grip unit, you can probably trade it for a complete open 3rd member with the gears you want from somebody here.