2002 Astro front limited/gearing options

THIS FORUM IS FOR ANY QUESTIONS ON THE 7.25" IFS FRONT DIFF, CV HALF SHAFTS AND FRONT DRIVE SHAFT.
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ElementalHg
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2002 Astro front limited/gearing options

Post by ElementalHg »

Hey fellas. I'm an Audi guy and have quickly discovered I don't know .... about this Astro I purchased for a camping rig. With my Colorado altitude and 30" tires, the Astro truly is a sad sight going up Vail pass and I have not even hung my DRZ off the back yet. I wish I had another 25hp haha.

I have been looking into gear sets for the front and rear. The rear seems readily available with a few options for limited slip, Torsen and 4.10 gears. The front I have questions about. Seems it is a smaller setup than the rear and I am very unsure of options for limited slip and gears? Any knowledge in the area is greatly appreciated.

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Re: 2002 limited/gearing let's explore 4 sp Atlas t case ..

Post by Astrophysics »

Hi,
Yes, it would be nice to have more power on the hills. But, a lifted and loaded van should be driving carefully.
My 2003 AWD has 2 " lift and BFG KO tires which are heavy even in the LT225/70-16 size. About 28"diameter.
I have heavy bumper and grille guard. My 3.42 gearing makes it slow to accelerate.
I am swapping the OEM np136 single speed t case for a manual shift 2 speed np231C.
The 4Lo is 2.72:1.

You got me thing about investigating a 3 or 4 speed transfer case from Advance Adapters such as the Atlas. The Atlas is about $2,000 but axle ratio changes are not cheap either.
I wonder if a t case could perform the function better than axle ratio changes. The Atlas t case can be shifted to 2 wheel drive low range as wheel as 4 Lo. The Atlas has a twin lever shifter to allow separate control

Proposed 4 speed Atlas T case selections:
A. 1:1 ratio aka 2wheel high
B. 1.10 :1. . 2 wheel drive highway hill climbing mode equivalent to axle change from 3.42 to 3.73 aka 10% change

C. 1.2 :1. 2 wheel drive highway hill climbing 20% change equivalent to 3.42 to 4.10 axle ratio change
D. 2.72:1 ratio 4 wheel low. 2.72 : 1 ratio is the standard np231C transfer case ratio.


The whole concept here is to use 2nd and 3rd settings the 4 speed Atlas t case to provide slight ratio changes (aka 10% and 20% to simulate axle ratio changes but vehicle can be in 2 wheel drive and driving fast. The 4th position of the Atlas would be for slow travel in dirt either 2 who drive or 4 who drive.

The Atlas t case is gear driven instead of chain so it is quiet and synchronized

AP
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T case available in 4 speeds Atlas from Advance Adapters in Paso Robles , CA
T case available in 4 speeds Atlas from Advance Adapters in Paso Robles , CA

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Re: 2002 Astro front limited/gearing options

Post by Captn. Crunch »

Welcome to the astro/Safari universe. I’d try dropping back to stock sized tires. The 3.42’s wheren’t horrible till you hit 30” on the tire chart. I love my 3.73’s and 29”.
If you want to re-gear you have several options. The front differential is the 7.2” clamshell style. It is the same as the S-10 4x4 trucks. There’s gear sets available as high as 4.56. Have fun shopping and let us know what you’re thinking
Captn. Crunch
"I don't beat my rig-I use it to it's maximum potential"
1994 Safari conversion (sold) and miss'n it!
1999 Safari SLE AWD junked
2003 GMC Safari AWD SLT
cast iron Torsen equipped front diff
S-10 leafs-G80 rear w/3.73’s
2” body lift w/Falken Wildpeak AT’s

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Re: 2002 Astro front limited/gearing options

Post by WE7X »

You should be able to find a matching front diff ratio to the rear you choose, but the 4.10's are a bit scarce. You will probably have to start looking a S-10 pickups. The RPO code for the 4.10 ratio is GT5.
If you find G80 and GT5 RPO codes, you will have a 4.10 and Posi rear end also. Get the matching front diff and you should be set, if that is the ratio you desire. The RPO code for the 3.73 ratio is GT4.
Happy hunting!

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Re: 2002 Astro front limited/gearing options

Post by Herbie »

While 4.10s are thin on the ground in junkyards, etc., they're readily available and plentiful in terms of gear-sets.

I've got an old quote for a 2-axle re-gear (plus a lunchbox locker) for my 2003 that I should finally be able to afford with this year's tax refund. I called my gear guy to double-check on availability and he told me just to let him know when to pull the trigger - all parts (ring/pinion sets, lockers, etc.) available in less than 24 hours.
"My minivan is cooler than your bro-truck"
2003 Astro AWD Astrolander/ZMB - GTRV Top Transplant, 4" OLV Lift, NP233 T-case, evolving interior
1995 Safari GTRV Organ donor - gutted and gone.
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Re: 2002 Astro front limited/gearing options

Post by Captn. Crunch »

3.73’s you can get from the junk yard. The astro rear is a stand alone unit. Nothing else will swap in due to width and the diff offset. Any chevy Zr2 S-10 4x4 will have 3.73’s. Any Zr2 with RPO code np1 and a manual trans. will have a cast iron front diff with 3.73’s.
4.10 and 4.56 front and rear ratios are available for around $200.00 a set. Installation by a reputable axle guy highly recommended
Way cheaper if you bring him a front diff to build on the bench then you swap it in. Labor charge for r&r’ing a front diff is a lot.
Captn. Crunch
"I don't beat my rig-I use it to it's maximum potential"
1994 Safari conversion (sold) and miss'n it!
1999 Safari SLE AWD junked
2003 GMC Safari AWD SLT
cast iron Torsen equipped front diff
S-10 leafs-G80 rear w/3.73’s
2” body lift w/Falken Wildpeak AT’s

Topic author
ElementalHg
I am merely driving my van
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Re: 2002 Astro front limited/gearing options

Post by ElementalHg »

Thanks for all your helpful input guys. I understand much better about the differences between the front and the rear. I did look up my tires and the Goodyear Dura tracs@ 235/75-15 are a 29" tires. They still look tiny on the van. So I'll just live with them regardless.

I spent some of the weekend looking for parts. I'm only looking at brand new parts if I can. I am probably looking in mostly the wrong places but it seems front limited slip differentials new are just not available and rear stuff seems not too much of a problem. So I will probably just do the rear limited slip and front and rear 4.10's.

If anyone has a line on limited slip front diff stuff or just had good customer service ordering gears/diff stuff let me know what company is serving people the best. I definately will have a drive line professional do this. Seems like going cheap on something like this is a poor choice.

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Re: 2002 Astro front limited/gearing options

Post by Captn. Crunch »

Here is the link to one of three traction devices for the 7.2” front diff.
http://store.teammfactory.com/syclone-helical-lsd/

http://www.engineered.net
Here is the second

Here is the third
https://www.summitracing.com/parts/pwt-1935-lr

Here is the rear Torsen link
https://torsen.com/product/f-car-gm-7-6-3-series/
Captn. Crunch
"I don't beat my rig-I use it to it's maximum potential"
1994 Safari conversion (sold) and miss'n it!
1999 Safari SLE AWD junked
2003 GMC Safari AWD SLT
cast iron Torsen equipped front diff
S-10 leafs-G80 rear w/3.73’s
2” body lift w/Falken Wildpeak AT’s
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