Hi Guys,

I am the Chinese from Taiwan, I keep noted about " rear 3.73 " , what is that ?
how about my 87 V6 ? rear - how many??


Thank you

Joe

 

The 3.73 rear is geared higher for quicker acceleration. However, the vehicles top speed would be reduced because the engine now runs at a higher RPM than before.

Your 87 has either a 3.23 rear or a 3.42 rear

 

howdy, well 3.73 is the ratio of the gears in the axle which is a performance ratio, 3.73 was the best performance ratio available in third gen cars, 3.42 seems to be more common, but neither are hard to find or are uncommon.

 

Maybe in the US -- but I think any thirdgen part is rare in Taiwan!

 

The 3.73 rear axle is also very hard to find in the US! 3.73's only came behind trans am's or camaro z28's with manual transmissions and engine code "G", between '82-'85. On the T/A or Z28, this was on a posi rear with disc brakes. You could also find the 3.73 gear on the 1984 Camaro H.O, with an open differential, and drum brakes- I'm not sure of the engine or tranny combination. One more car with the 3.73 was the 2.5l 4-cylinder Camaro/Firebird, if the 4 cylinder had a manual transmisison, it would have a 3.73/open/drum rear, too.

Problem with 82-83 rear axles is that they don't share the same brake line threads as 84-2002. 1984 was the first year that GM used metric threads and flares (called "ISO flares" for International Standards Organization) on brake lines. For 1982-1983, GM was using standard (SAE) flares & threads.

So if you buy an 82-83 rear axle, you'll need to do one of three things:

1. Convert the 82-83 brakes to metric threads. This is easy for drum brakes, hard for disc brakes. On drum brakes, you just need to change the wheel cylinder ($20). If you're on a budget, and you're putting a drum rear on, you could take all your hydraulic hardware off of your old drum axle, and put it onto the "new" 3.73 drum axle. But- for a disc brakes, you need to buy 84-88 rear calipers.

2. Make special brake lines for the axle. You would need to make two hard lines, one for each wheel. One side would have the ISO metric flare to fit your 84-2002 car. The other side would have the SAE (standard threads) flare to fit the 82-83 brakes.

3. Try to find some kind of adapter that converts a metric flare line into a standard (SAE) flare line. These are hard to find.

ISO flare tools are expensive, about $80. A double flare tool is pretty darn cheap. You can buy pre-flared metric lines at local parts stores. Be aware that these are usually sold under the "brake lines for foreign/import cars" heading; the brake line people haven't realized that GM's used metric lines since '84. But the best way is to buy pre-flared metric lines, cut one end off, rent (or buy for $30) a standard double-flare tool and some standard thread "tube nuts", slide the tube nut over the tubing, and put a double flare on the other end of the pipe. This method (which is #2 above) is actually a preferred repair method for garages. Usually a note is made somewhere on the axle about the special brake lines. One point to note, though, since it is a hydraulic system, both sides of the axle should have the same diameter of brake line, and the inside diameter of the brake line shouldn't vary too far from the original inside diameter.

Of course, none of you wanted to know that much, eh?

And what nobody mentioned yet, joekickass, is that you can buy 3.73 gears and have them installed. (They're hard to install, many settings need to be checked. It requires about $300 worth of tools.) This way you don't need to buy a rear axle from a junkyard. You can do a <a href="search.php?s="><img src="images/top_search.gif" alt="Search" border="0"></a> on the "Suspension" forum for "3.73 swap" and you'll find more information. I swapped a 3.73/posi/disc from a 1984 trans am into my '86 Firebird, and my messages should still be up in that forum (from a search).