I found a site online that supplies 9-bolt parts and the site says i will have to change my carrier to a 3 series if im going to change my ratio from 2.77 to 3.45. is this true?

 

One BIG YES... 2-series (2:77) now will Not work wirh 3-series (3:45) gear.

 

Yep change carrier and speedo gears in trans to make it all work correctly

 

Thanks you both for the input.

 

Now I don't want to open a HUGE can of worms here, but I have a set on 3.70's working noisily with a 2 series carrier and a special shim behind the ring gear. Is this BAD? Perfect pettern, .014 backlash. I have yet to abuse the car with the new gears and we set them up last monday. I have yet to get solid input on the carrier setup

 

Didn't know you could even get ring gear spacers for the 9-bolt; but if so, that opens up an alternative. Some people don't like those, as they put more stress on the ring gear bolts; but others don't have a problem with them.

In the past, as far as has been known around here, the only way available to get from a 2 series 9-bolt to a 3 series, was a 3 series carrier.

Are you sure you have a 9-bolt?

 

They do not make "thick" gearsets for theses like they do for the Dana's in the Vettes so you can use 3 series gears
on a 2 series carrier?

 

Yeah I'm sure. I put them in last weekend.

 

Some carriers have only a small distance around them where the ring gear normally rides. If this is used by the spacer and the ring gear ends up un-indexed at it's centre, it has potential to be a problem.

 

Unless Im remember my decimal places wrong, .014 backlash seems like quite a lot. 10 bolts seem to like backlash in the .008-.012 range I think. I found a 9-bolt manual that claimed 9-bolts liked .004-.008 ish range or so? I know it was considerably tighter which put me off a bit, wasn't really sure which number to aim for. When mine was put together the backlash was right at .007 or .008 and the pattern looked perfect so I decided that was where it was going to be.

It's noisy at 50+ mph, enough that its noticable, but not enough that I cant listen to teh radio and drown it out. It doesnt do it at normal around town and country road speeds, so I dont really mind much. As good as the pattern looked and given all the measurements worked out, Im thinking that's just as good as this one is going to get.

 

.014" is a bit on the "alot" side but not out of the realm... remember, this is measured cold, but things "grow" when they get hot, so a certain amount of that will go away in actual use. It's better to have "a little" too much, than even "a tiny bit" too little, as too little will make the gears attempt to occupy the same space, and that's never a good thing with moving metal parts.

I've never seen or heard of either a ring gear spacer or the "special" extra-thick gears for a 9-bolt. This is th eonly person I'm aware of who has ever used one of these. I'm suspicious here.

That said, if it works, it works. Since 3.70 is 10 and 37 teeth, only 10 on the pinion, that ratio is GOING TO have a tendency toward being noisy; no way around that.

 

I guess that could work. When i did 2.77 to 3.27 i got a used 3 series carrier. I didnt compare the ring gears tho to see if a spacer could work but i guess the theory is sound.

Hey there may even be a market for these spacers lol. My old 2 series was solid. Worked great. The used 3 series had worn cones and i lost most of the posi action after 2 yrs

I did 2.73 to 3.73 in my 10 bolt by buying extra thick ring gear for 2 series Carrier