luke_501 Posted August 7, 2012 Share Posted August 7, 2012 hey guys, i recently found out everything in my rear end is junk. ok, not junk but many teeth are missing on ring and pinion. So im using this as my excuse to upgrade to a posi with 3:73 gears. My question is... when buying these is there anything specific i need to know? i have a 12 bolt currently and everything im finding that fits the car is for a 10 bolt. All of the 12 bolt posi kits im finding are listed for trucks. Is this because i have a trucks rear end? or im just not finding the right kit? Is there a big difference between a 10 and 12 bolt kit? btw.. when i say kit.. i mean its a kit that comes with gm eaton posi, gears, and bearings. I am a rookie when it comes to this stuff so any help would be awesome! thanks in advance!! Quote Link to comment Share on other sites More sharing options...
dbreese Posted August 7, 2012 Share Posted August 7, 2012 http://www.moserengineering.com/ http://www.strangeengineering.net/ http://www.tomsdifferentials.com/ Any of these companies can hook you up with what you need. Give'em a call. Hope this helps. David Quote Link to comment Share on other sites More sharing options...
allchevy Posted August 7, 2012 Share Posted August 7, 2012 What tranny do you have? i've got the same ratio, 65 mph and i'm running over 3k on the tach. there have been other posts on this that you can plug all your info in and get so good #'s for different variations. Quote Link to comment Share on other sites More sharing options...
Leghome Posted August 7, 2012 Share Posted August 7, 2012 My 72 has 3:73 gears and 350 SB and a 700R4 tranny. At 70MPH the tach reads 2700rpm Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted August 7, 2012 Share Posted August 7, 2012 I run approx 3400rpm @ 70 w/3.73's and a turbo 400 w/a 28" tire Quote Link to comment Share on other sites More sharing options...
gprimm Posted August 7, 2012 Share Posted August 7, 2012 I have had several friends put 3.73's in their cars and they have taken them out because of the RPM's at speed. 3.42's, 3.31's or even a 3.08 (with a big block), made them happy. One put a 3.08 (big block car) and added a 700R4 and is getting 20mpg. 3.73 sounds sexy, but if you drive on the highway alot with a 3-speed automatic, it isn't all it's cracked u to be. Quote Link to comment Share on other sites More sharing options...
Austin Posted August 7, 2012 Share Posted August 7, 2012 i'd look into moser, I used all moser rear end stuff in my camaro rear end and it was an easy install and went together great and easy and has held together great, but i did switch out the 4.88's for a 4.11 gear which moser had and shipped very quickly Quote Link to comment Share on other sites More sharing options...
FASTSS454 Posted August 7, 2012 Share Posted August 7, 2012 I have had several friends put 3.73's in their cars and they have taken them out because of the RPM's at speed. 3.42's, 3.31's or even a 3.08 (with a big block), made them happy. One put a 3.08 (big block car) and added a 700R4 and is getting 20mpg. 3.73 sounds sexy, but if you drive on the highway alot with a 3-speed automatic, it isn't all it's cracked u to be. Originally Posted By: Sam (Bones) I run approx 3400rpm @ 70 w/3.73's and a turbo 400 w/a 28" tire Ditto, I like the take off but hate the high revs at a sustained long run. You didn't mention if you have a 3 or 4 speed trans so that will play into the recommendations you get. Quote Link to comment Share on other sites More sharing options...
luke_501 Posted August 7, 2012 Author Share Posted August 7, 2012 My transmission is a TH350. Im planning on sticking with it unless i find out it's no good also. But from what i have seen it's in decent shape. The problem is... I have NEVER takin this car on the road other than on and off trailers. I want to be able to cruise at 65/70 mph without stopping at every gas station. Im running a 350 S/B. Should i stick with 3:73's or look into something else? Quote Link to comment Share on other sites More sharing options...
FASTSS454 Posted August 7, 2012 Share Posted August 7, 2012 Well from my experiance as a old fart, back in the day 3.73's were fine with a non overdrive trans but now a days after years of driving with a overdriven trans it sounds like it is screaming all the time. My advice is if you plan on driving this car on the freeway a lot then drop down to 3.42 or the 3.08 gear set or plan on doing either a gear vendors overdrive or 4 speed trans swap or live with it at 3400 RPM. Quote Link to comment Share on other sites More sharing options...
cbolt Posted August 7, 2012 Share Posted August 7, 2012 I was getting about 15mpg with a TH350 and 2:73 gears at about 75 mph. The car would go just under 200 miles on a tank of fuel. You will probably do much worse with the 3:73's. I guess the decision to either stick with the current setup or do some mods would depend on what type of driving you are planning. If you are primarily planning to do road trips, you will benefit from changing gears. If you are going to primarily attend local cruise-ins and the like, you may want to leave it alone. My suggestion is to take it on the road and see how it does, figure out what you want it to do, and go from there. Quote Link to comment Share on other sites More sharing options...
luke_501 Posted August 8, 2012 Author Share Posted August 8, 2012 Thanks guys!!! Sounds like I have some thinking to do! I don't know how much free way driving il be doing but i am going to drive this car!!! So it needs to be able to handle it. Thanks for all the info. Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted August 8, 2012 Share Posted August 8, 2012 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.