71 MONTE 4 YA Posted November 23, 2010 Share Posted November 23, 2010 Will a BOP 12 bolt posi with 3:42 gears work in my 71 monte? Is it worth $300. The person selling it says it has been modified to work in a G-body but can be put back into a 68-72 A-body. I haven't talked to the person this is all from his ad. What possible modifications could he be talking about? Thanks family...... Rodney Quote Link to comment Share on other sites More sharing options...
Slaman Posted November 23, 2010 Share Posted November 23, 2010 Not sure what mods he may have done. But the 12 bolt in my monte is out of an a 70-72 Olds Cutlass... It fit fine except I had to have my drive shaft shortened... I think it's a heavy duty model... Quote Link to comment Share on other sites More sharing options...
71 MONTE 4 YA Posted November 23, 2010 Author Share Posted November 23, 2010 Are the 3:42 gears ok for a daily driver? Quote Link to comment Share on other sites More sharing options...
Slaman Posted November 23, 2010 Share Posted November 23, 2010 I probably would not go any steeper than a 3:42 or 3:55 without an overdrive tranny. So it should work pretty good for a daily driver. Quote Link to comment Share on other sites More sharing options...
71 MONTE 4 YA Posted November 23, 2010 Author Share Posted November 23, 2010 The person wants $500 obo. I offered $300 and he is considering it but waiting to see if he get's a better offer. Is it worth $300? Quote Link to comment Share on other sites More sharing options...
71 MONTE 4 YA Posted November 23, 2010 Author Share Posted November 23, 2010 Not sure what mods he may have done.... He said that I would have to put the spring perches back on the front of the housing. That is the only mod that has been done. Quote Link to comment Share on other sites More sharing options...
jim's 70 Posted November 23, 2010 Share Posted November 23, 2010 Ummm...moving spring perches is kind of involved...I don't know what kind of experience you have...so fogive me if I am out of line...but cutting exsiting perches off and making sure the correct ones are welded on in the right spot seems pretty involved to me. I have not been out pricing rears, but I personally would look more for a direct fit. As for the 3:42's I run them with a 27"tall tire and turn just about 3000rpm at 70 Quote Link to comment Share on other sites More sharing options...
71 MONTE 4 YA Posted February 10, 2011 Author Share Posted February 10, 2011 Well I bought the BOP rear end. It has 12 bolts on the cover and 10 bolts on the ring gear. Is this bad? It has 42 teeth on the ring gear and it is posi. I do not plan on racing or building my engine into a powerful beast. Do you all think this will be ok for my use? Here are a few pictures:    Here is the mod the guy did to make the rear fit into the G-body Regal he had it in. He moved the perches to the top of the axle tubes   Are these the bolt in axles?    If all goes well, there wont be any more one wheel peel    Quote Link to comment Share on other sites More sharing options...
Ian Posted February 10, 2011 Share Posted February 10, 2011 The axles are not bolt in, those are the bolts that hold the backing plates on. The spring perches look like they are in the correct place for a Monte or any A/G body. What does it measure backing plate to backing plate? It should measure the same as your current one does. Quote Link to comment Share on other sites More sharing options...
71 MONTE 4 YA Posted February 10, 2011 Author Share Posted February 10, 2011 The axles are not bolt in, those are the bolts that hold the backing plates on. The spring perches look like they are in the correct place for a Monte or any A/G body. What does it measure backing plate to backing plate? It should measure the same as your current one does. I thought the perches sat a little bit forward of the axle housing on the Monte. I also thought the 12 bolt BOP rear Which is really a 10 bolt because it has 10 bolts on the ring gear had the bolt in axles. Someone correct me if I am wrong. I have really been searching all over the web trying to find more info on this. Quote Link to comment Share on other sites More sharing options...
Ian Posted February 10, 2011 Share Posted February 10, 2011 Ahh you are right.. Here is the stock 12 bolt out of mine when I was doing upgrades... Â Quote Link to comment Share on other sites More sharing options...
71 MONTE 4 YA Posted February 10, 2011 Author Share Posted February 10, 2011 Ahh you are right.. Here is the stock 12 bolt out of mine when I was doing upgrades... I should be able to put those back in the correct place? Right? Quote Link to comment Share on other sites More sharing options...
Ian Posted February 10, 2011 Share Posted February 10, 2011 You would have to either cut them off your original rear, or a junk yard rear, then weld them on. Quote Link to comment Share on other sites More sharing options...
KWick_70MC Posted February 10, 2011 Share Posted February 10, 2011 Rodney, a good 4X4 shop resets perches all the time. They should be able to measure the angle of your drive shaft and calculate the perch settings on your rear end. They will also tell you if what you have will work, or will they need to use pieces from the old one. Â BTW new perches are fairly cheap too. Â I had perches done on my 74 IH Scout, and they turned out great. Â Kevin Quote Link to comment Share on other sites More sharing options...
Monte7071 Posted February 11, 2011 Share Posted February 11, 2011 Contact Monzaz he is a member on here and can answer your questions here is is site link Quote Link to comment Share on other sites More sharing options...
71 MONTE 4 YA Posted February 11, 2011 Author Share Posted February 11, 2011 Contact Monzaz he is a member on here and can answer your questions here is is site link Thanks for the link. From the link it shows that I have the Olds 8.4 with the bolt in axles. Quote Link to comment Share on other sites More sharing options...
Heff Posted February 12, 2011 Share Posted February 12, 2011 If it has 42 teeth it probably a 3.23 gear ratio. definatly a bolt in style should have 31 spline axles in it. Quote Link to comment Share on other sites More sharing options...
71 MONTE 4 YA Posted February 12, 2011 Author Share Posted February 12, 2011 If it has 42 teeth it probably a 3.23 gear ratio. definatly a bolt in style should have 31 spline axles in it. The guy that I got it from said it had 3.42 gears in it. How can I tell? Quote Link to comment Share on other sites More sharing options...
Monte7071 Posted February 12, 2011 Share Posted February 12, 2011 Count the nuber of teeth on the ring and on the pinion divide the number on the ring by the pinion. Say you have 37 on the ring and 9 on the pinion that would be a 4.11. Quote Link to comment Share on other sites More sharing options...
71 MONTE 4 YA Posted February 12, 2011 Author Share Posted February 12, 2011 Count the nuber of teeth on the ring and on the pinion divide the number on the ring by the pinion. Say you have 37 on the ring and 9 on the pinion that would be a 4.11. I would have to disassemble the carrier to see the pinion teeth right? Quote Link to comment Share on other sites More sharing options...
KWick_70MC Posted February 12, 2011 Share Posted February 12, 2011 Put a wheel lug nut on one of the lugs, and using that as a reference point. Have a friend/wife/GF turn the drive shaft 1 complete revolution. Count how many times the lugnut makes a complete revolution. Example is, 1 turn of drive shaft and 3 and 1/4 in turn equates to 3.25 or probably close to a common ratio of 3.23.  Hope this helps  Kevin Quote Link to comment Share on other sites More sharing options...
71 MONTE 4 YA Posted February 14, 2011 Author Share Posted February 14, 2011 Put a wheel lug nut on one of the lugs, and using that as a reference point. Have a friend/wife/GF turn the drive shaft 1 complete revolution. Count how many times the lugnut makes a complete revolution. Example is, 1 turn of drive shaft and 3 and 1/4 in turn equates to 3.25 or probably close to a common ratio of 3.23. Hope this helps  Kevin  It takes 3.25 turns of the driveshaft for one complete revolution of the lugnut. What do I have? Quote Link to comment Share on other sites More sharing options...
Heff Posted February 14, 2011 Share Posted February 14, 2011 I'd say it's a 3.23 that was one of the standard gear sets they used from the factory for you rear end. Quote Link to comment Share on other sites More sharing options...
monzaz Posted February 28, 2011 Share Posted February 28, 2011 3.23 is a pretty good ratio for all around driving. You can also get 3.42 and 3.90 gear sets from aftermarket Richmond gears. They will both fit the posi carrier you have.  The axle spline count is most likely 28 as the 31 spline axle 12 bolt 'O' type are usually pretty rare. We can check all that when you bring it by. Jim  330 659 7117 Jim J D RAce.com Quote Link to comment Share on other sites More sharing options...
71 MONTE 4 YA Posted February 28, 2011 Author Share Posted February 28, 2011 Thanks Jim. See you soon. Quote Link to comment Share on other sites More sharing options...
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