Need Alternate Rearend for 2000 Astro

astrovankyle · 01-03-2007, 11:56 AM

My tow package rearend has gone out. I am looking for an alternative to the original. I'm told it came with 3:42 gear, but my mechanic says 3:73. I think he is wrong. I still tow and haul with it. But I need to know if something like an S-10 rear end would work with the 3:42 or alternatively what years vehicles would also work. Just looking for the cheapest workaround. My mechanic will put take it out and put it in for reasonable price. Thanks for any info.

CD Smalley · 01-03-2007, 06:38 PM

Your best bet is to find an Astro/Safari rear end if you are wanting to swap the whole piece. They are offset, meaning one shaft is longer than the other. The S-10s are an equal length shaft. Take a look at your SPID to see what gears were installed from the factory.
GU6 = 3.42
I can't find 3.73s RPO code in my book though.

Blue Bowtie · 01-05-2007, 10:52 PM

GT4 is the RPO code for 3.73 axles on my Astro.

astrovankyle · 01-08-2007, 03:17 PM

Thanks for the info. Yup gt4 is the rear end code. Thanks also for the info on s-10 being centered and the astros being offset. A 2000 astro rearend alt. is good from 1995 to 2002 astros and safari's. I decided to have one sent down from Tenn. to fl.. It had the best part rating and price versus distance. Total with ship was $500, fedex. Carparts.com seems to be the best common source to find anything used for the best price. I wish now that I had gone with the 3:42 gear as it is cheaper, will pull #5000, but the fuel mileage will go down with it. Again thanks for the help.

old_master · 01-08-2007, 08:16 PM

Quote:

Originally Posted by astrovankyle

...I wish now that I had gone with the 3:42 gear as it is cheaper, will pull #5000, but the fuel mileage will go down with it. Again thanks for the help.

3.42:1 will give you better fuel mileage but less power than the 3.73:1 The speedometer driven gear would need to be replaced to correct speedometer error.

astrovankyle · 01-09-2007, 03:32 PM

Thanks Old master for the info. I thought it was the other way around. So the higher gear number is more pulling ability than the lower number. Thanks for the correction. So apparently I did get the full towing package when I bought this, with the 3:73 gear. My mechanic called today and said he had the new one installed and the van was ready to pick up. Been without my pony now for 5 days. Can't get around much without it. Thanks all for the help.

old_master · 01-09-2007, 03:52 PM

An easy way to remember it is: "Higher number = higher engine RPM" Higher engine RPM will produce more low end power, less top end speed, and consume more fuel doing it.

The axle ratio 3.73:1 means that the driveshaft rotates 3.73 times for each single revolution of the axle shaft.

CD Smalley · 01-09-2007, 04:41 PM

No speedo gear to replace on a 2000. A different VSS would do the trick.

At somepoint the Astro/Safari vans used a DRAC module which could be reprogrammed to handle this.

Gotta think about the ABS to. That will be effected by the change in gear ratios as well...

sreve · 01-09-2007, 07:58 PM

dracs went out with obd1, all 4L60e trans ues a 40 tooth tone ring so the vss does not care. flashing the pcm is the only way.

CD Smalley · 01-09-2007, 08:51 PM

Aahh... I knew it was different from swapping a gear.

Looks like I was one technology step behind!

Blue Bowtie · 01-09-2007, 10:22 PM

My AWD with 3.73 gears gets nearly the same mileage, or within 8/10 MPG, as my old 2WD with 3.23 gears (and a shorter body), although the SFI has to be waaaay better than the TBI. I specifically ordered it with 3.73s, a rear locker, and no G.D. roof rack. (Guess what - It came in with a rack anyway! - The geniuses in the production control department in Baltimore must have figured the order was a mistake.)

All else being equal, the lower gearing should provide a little better MPG, but the engine is going to make the same horsepower at any given road speed to punch a hole in the wind, and the later PCMs trim fuel well enough that the extra RPM will be mande with nearly the same total fuel flow.

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