open rear upgrade 71monte

[Guest]

hey guys, I got one for ya. I am new to the science of rear ends. I have a basic knowledge of how they operate but not much else. Without replaceing the whole rear, how can I make it better traction wise? is there a way? I understand the difference basically between open and possi. I wanna go with a better ratio but don't know if Im wasting my time doing so one legged. a friend of mine installed a "power trax" unit in his car, and he is not really pleased with it. he tells me it's noisy around turns.if someone could help i'd appreciate it. (I'm just tryin to get all my eggs into one basket) i'm stickin to my 350 trans.

[Guest]

Hey, About your rear end. I just had my 10 bolt pulled out and re built. A possi, 390 gears new drums, brakes everything done for about 1600.00.

And that was through a friend.

Iam now working on a 70 ss 454 that i came across.

they say the 454 will love those gears.

I would have it rebuilt if u can afford it.

[monzaz]

Well the power traxx is a pretty good unit . You said it makes noise in the corners. Sounds like it is a lock right...Not a power traxx unit. The early style unit. I install alot of them for the weekend warriors around here and they love them. The exhaust is usually loud and does not bother them at all. There is NO ring and pinion ajustment with a LA locker(power trax, lock right ) like with a posi or detroit locker. Gears will improve the launch of any car for sure. Remember the more low end you gain the less top end you will have. evaluate what you what your car to cruise at and do then pick or keeep the same gear. Posi will improve traction of any gear choice you choose. If you need more help or parts email me I am always here.

 

WOW 1600.00 and that was using your housing?...I have to start raising my prices...lol

[Guest]

I have a 72 Monte, I had 2.73 Open Diff, changed to 3.55 Eaton Posi, cost about $1,200 everything installed, Posi Unit, Ring and Pinion gears, new bearings and seals, chrome rearend cover. with a 1:1 final drive ratio on a TH400 or TH350 you'll turn around 3,100 rpm at 60mph, so keeping up with highway traffic isn't fun. Stoplight to stoplight you'll get whiplash on launch and hitting second gear. Auburn makes a cone clutch Posi that is not rebuildable but is quite good, Eaton is the way to go in my opinion, mine is awesome, and posi-traction is a must for a serious muscle car. You could put very tall and Fat tires on the rear, but you'll lose torque and gain traction. Like the other guys say, evaluate what you want, if only traction, just to the posi and keep your gears, if you want better milage without going to a 4 speed overdrive, look into changing gears lower, find your ratio on your axle tube, front on passenger side, I've just been through it all so e-mail me and I'll help all I can.

[kc8oye]

are you running a high stall converter? 3100 rpm @ 60 mph sounds VERY high for a 3.55 rear?

 

my 2.78 with a TH350 turns 2400 rpm @ 75mph with 235/75-15 tires on the back (big tires do bring it down a lot)... on second thought what size are your rear tires? I used to run 2800 with my old 205/70-15's..

[big gear head]

The Eaton posi is the smoothest operating posi for GM rear ends, and it is rebuildable. It might cost a bit more, but it is worth it. The Lock Right by Power Trax is easy to install, but it does make some noise. I have had one in my 4X4 daily driver for about 8 1/2 years and it works great, just noisy and jerky. Many people have had problems with the newer No-Slip by Power Trax. I don't recommend it. To install the Eaton you will have to measure the backlash before you remove the original differential and set it to the same value with the new Eaton. This is done with shims. You will need a dial indicator with a magnetic base to make the measurements. You will also need to know which rear end you have in your car.