Im wanting to swap out the ring and pinion gear in my bird. I have a basic idea of what im needing to do but i would like some input on this to make sure im getting the right stuff and that i wont be over RPM'ing my engine after i do it.

I used to have a thread about the car but it looks as though it was pruned so i wont go into all the confusing details about what it is/was.

Basically its an 86 6 cyl bird thats been turned into a 8 cyl 350 TPI T/A.

I noticed that my Diff was pretty sloppy and getting worse, but i was planning on rebuilding it anyways so this is kinda the perfect time to do it.

I had a look at what it is and actually found a nice little tag that gave me all the info. On this car its a rare thing to actually find any tag at all that states decent info.

Here is what it says on the tag.

P/N 10040660
RATIO 2.77 SER No. 13526

Now if i did my reserch properly that means its a Borg Warner 86 Kit. With 2.77 gearing.

I want to put in 3.73 gearing into it and have found these....

http://www.justdifferentials.com/ind...oducts_id=2221

And also this.....

http://www.justdifferentials.com/ind...oducts_id=1467

I guess i just need to know if that will work for me or if i will have problems or cause my RPM's to go up to high. I regularly drive at 65mph to and from work.

Thanks in advance

 

You are also going to need a 3 series differetnail. The 2.77 gears use a 2 series differential and the 3.70 uses a 3 series.

 

Not a DIY job for a novice who may have problems finding the correct parts and setting everything up to specs. Just for your info: NOTHING is interchangable with the internals for a 9-bolt & 10-bolt rears.

 

So what would i need to get it to the 3.73 range? I just need to order the parts. I am having a shop put them in, he works with me on labor if i get the parts myself.

 

The parts you need are not readly available at all Auto Parts sites. Examples: BW 9-bolt 3-series carrier with limited slip & 7 3/4 dia 3:73 gear ratio. I would suggest that you do more research on the subject and what other options are open to you.

Again..9-bolt & 10-bolt parts are NOT interchangeable.

 

Well after a BUNCH of digging I finally figured these 9 bolt rear ends out. 7.75" and 9 bolts apparently are hard to come by when your digging for parts. Seems the carrier and cones are the hardest thing to find for them.

Got a series 3 Posi carrier. That alone was an act of god to find. Only 2 places on the web that had them. 9bolt.com, and ONE listed on ebay. Cost me $325 with shipping for the Ebay one but includes spider gears and new cones.

Got the 3.70 R&P gear from justdifferentials.com. Had a set of Nitro gears for $175. They also had the master install kit for about $160 that has all the bearings and small parts in it.

All in all im spending about $650 on it all, not really that bad considering parts availablity for these things. But then again i decided that after all the research i did and what people say about them, that they were worth the investment to fix and keep since they seem to be pretty strong compared to a 10 bolt system and im not the type of driver thats going to need a 12 bolt system.

Thanks for the input

 

Now this is ironic, because i bought a used 9 bolt and did a complete rebuild and gear swap myself. I also installed 3.70 nitro gears from just diff. The only problem with the install kit is mine came with the wrong pinion bearing, but i had to buy axel bearings and seals from NAPA anyway. I also may have the pinion depth off by a couple of thousanads, but had a nice pattern on the ring gear. My point is i have a slight whine at around 55-65mph which can also be common with 3.70 gears. As for the gear ratio, It's better than the 3.27 i have in my original, and only upped my rpm by about 200 more rpm. Your going to also have to change your speedometer gears in the tranny to compensate for the gear change.