Rear end upgrade??

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I crawled under the car and its 10 bolt, and the number on the bottom was 2852905. I also gave my grandpa a call and he said the rear end is definitely original and if it's back there it was put there by the factory. So how easily can I install some lower gears in it? I'd probably want 3.55's
 
PoisonDart74 said:
http://youtu.be/JxrzG7ezp3o
Click to expand...

Thanks for that video, very informative. Sometimes I forget how old our Mopars really are.

And doogievlg, I don't know for sure but from driving the car it definitely feels like it's got a high gears like a 2.76. I don't have a lot of room to look under the car where it's at right now to try to find the tag. Since it's a slant 3 speed I doubt I've got 3.55's or even 3.23's
 
Doesn't hurt to change the rear end fluid anyway, so pop the rear cover off. The gear ratio will be stamped into the ring gear. Also by opening it up you can tell it is has a limited slip unit (suregrip) in it. If the ring gear is a 2.71(or higher) you lucked out. All you need to do is go junkyard, find a 96 or older jeep GC and you can take the sure grip unit and better gears outta it and bolt it into your 8.25 rear. But wait it gets better, if the jeep GC has rear disc brakes you can remove them and bolt them directly to your 8.25 rear.
 
No tach unfortunately, but I have good news. I WAS able to find the tag, It was hidden under the paint so I never noticed it before. I guess I really lucked out, I've got 3.21 gears in an 8 1/4 that came with a slant six. So when I get the 318 in, how much improvement would I feel in the butt dyno with a sure grip and 3.55 or 3.90 gears? or would 3.90's be too much? I've never had the car on the highway but I'd like to take trips with my grandpa in it so I need it to cruise good at 70 mph.
 
What are the chances that I could already have a sure grip in the car? I doubt I've got one but after everything else I've found out about it, I wouldn't be surprised.
 
OMG you did, leave the gears alone, 3.21 are a PERFECT balance between mean, and lean. Play with that calculator I sent earlier, and you'll see what I'm talking about.


Go do a burnout and see if it leaves 2 tracks or:

[ame]http://youtu.be/TI8ewn6HOjg[/ame]
 
PoisonDart74 said:
OMG you did, leave the gears alone, 3.21 are a PERFECT balance between mean, and lean. Play with that calculator I sent earlier, and you'll see what I'm talking about.


Go do a burnout and see if it leaves 2 tracks or:

http://youtu.be/TI8ewn6HOjg
Click to expand...

I can't go roast the hides off until I get the motor in the car, which is about 3 or 4 weeks away hopefully. Will it do good burnouts with 3.21's? It's a 9.2:1 318, High energy 268 Comp Cam, Hooker competition headers, 600 cfm edelbrock carb on a performer intake, and I've got QTP electric cutouts for it too. If the 3.21's will work well with that combo and it'll push me back in the seat a little I'll just try to find a sure grip if I don't have one and I'll leave the rest alone. :burnout:
 
BlueDream said:
No tach unfortunately, but I have good news. I WAS able to find the tag, It was hidden under the paint so I never noticed it before. I guess I really lucked out, I've got 3.21 gears in an 8 1/4 that came with a slant six. So when I get the 318 in, how much improvement would I feel in the butt dyno with a sure grip and 3.55 or 3.90 gears? or would 3.90's be too much? I've never had the car on the highway but I'd like to take trips with my grandpa in it so I need it to cruise good at 70 mph.
Click to expand...

You also have quite a bit of play in final drive ratio based on what wheels and tires you select. Bigger diameter tires = lower RPM and more MPG. Smaller diameter tires = higher RPM and more fun.

But if you want to cruise comfortably at 70 mph, be careful what you choose. I would go find a tire size calculator on the web and figure out what size tires you need to get your desired RPM at 70mph.

If that engine is screaming at 70mph you'll hate it, both in the driver's seat and at the pump.
 
PoisonDart74 said:
Guy with a similar combo just did a cruise, another thread praising how it throws him in the seat:

http://www.forabodiesonly.com/mopar/showthread.php?t=275445

http://www.forabodiesonly.com/mopar/showpost.php?p=1970421053&postcount=48


318's can rock just fine. With mild cam's you CAN have too much gear, 3.23 is good for a 268. When it comes to power, it's a balancing act, combination, not just one thing. Having the suspension setup is just, if not more important.
Click to expand...

I played around with that calculator some and I liked what I saw, I think the 3 speed with 3.21's will be fun and 2,880 rpm at 70 sounds pretty good to me. Will a sure grip be a direct bolt in with these gears? Or are certain sure grips made for certain gears?
 
As you play with that calculator, keep in mind your tire size with the weight of the car on them is the size you should enter into the calculator; the measurement from the center of the hub, to the ground with full load.


2.71 down and 2.71 up are different. SG is a bolt in deal, I would, like in the video, check run-out before and after installation and follow the video procedure for practice, check ring tooth pattern and all that; what's nice though, is you shouldn't have to take the pinion out, or dick with pre-load. Check the internal clutch pack for wear, switch the carrier and go.

It's an easy afternoon job.
 
PoisonDart74 said:
OMG you did, leave the gears alone, 3.21 are a PERFECT balance between mean, and lean...
Click to expand...

I have to agree. If it does not have a sure grip, It is easy because you do not have to set pinion depth. Change carriers then set bearing preload and gear backlash.
 
I called all the local salvage yards and they're wanting about $350 for a whole rear end and won't part it out. So much for trying to support local businesses, I'm going to just buy a sure grip off the internet. I'm just glad that I've got a good setup that I can drive with until I decide to pull the trigger on the sure grip. Never thought it'd be what it is, just thought it'd be like a lot of other slants. Thanks for all your help FABO!!
 
Keep your eye's open here in the for sale section. Wasn't long ago I saw a 8-1/4 sure grip for sale pretty cheap.

Sounds like you lucked out with the 3.21 gears. They should do you just fine IMO. 3.91's would be quicker but they'd also be screaming on the highway. It's a balancing act
 
BlueDream said:
I called all the local salvage yards and they're wanting about $350 for a whole rear end and won't part it out. So much for trying to support local businesses, I'm going to just buy a sure grip off the internet. I'm just glad that I've got a good setup that I can drive with until I decide to pull the trigger on the sure grip. Never thought it'd be what it is, just thought it'd be like a lot of other slants. Thanks for all your help FABO!!
Click to expand...

So you're gonna buy a suregrip before you know if you have one or not? Or did I miss that somewhere?

Jack the back of the car up and spin one tire and see which direction the other side spins. Same direction = suregrip. Opposite = open.
 
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