G80 & GT4 for 2004 AWD Astro Conversion

IF YOU HAVE QUESTIONS ON THE REAR DRIVE SHAFT OR AXLE, IT GOES HERE.

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Re: G80 & GT4 for 2004 AWD Astro Conversion

Post by Captn. Crunch » Sat Apr 13, 2019 2:00 pm

Good point Ron. What was the style of these worn out units? Clutched LSD? G-80? The wear factor is what led me to install Torsens in both my diffs. The front unit comes with a lifetime transferable warranty so I would feel pretty confident with a used Torsen. Ever a refurbished unit will put you at the mercy of the quality of parts used in the re-build
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
np236 transfer case
Torsen equipped cast iron front diff
Torsen equipped rear w/3.73's
2" body lift
S-10 rear leafs
2003 GMC Safari AWD SLT
Stock for now

forrestmccarthy
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Re: G80 & GT4 for 2004 AWD Astro Conversion

Post by forrestmccarthy » Thu Apr 25, 2019 2:10 am

Captn. Crunch,

I may have found a unicorn. It's a 2004 Chevy Blazer (89k) with "high wider performance package (opt ZR2), transfer case opt NP1 (3 switch dash control), AT (3.73 ratio, opt GT4)." Looks like I can grab the transfer case from it as well. I still need to do the magnet test. Interestingly, the Blazer front assembly is less expensive and closer than any I could find on an Astro.

A couple questions:

1) Can I use my existing front axles? This would be good as I recently replaced one of the hubs when the ABS quit working.

2) What did you use for a torsion differential in the front of your van? Not sure I'm ready to go this route. Yet, I'm intrigued and considering it. If I have found a unicorn, I can always add a front torsion later on.

FYI: I'm still working on sourcing parts for the rear. Can't find a rear assembly (GT4 & G80) with low mileage anywhere near me. A rebuild might be my best option. If so, I'm considering the Detroit Truetrac, as recommended. It is starting to feel like a winter project as the summer season is upon me and I want to be out adventuring not turning wrenches. Just the same, it would be good to get all the parts lined up.

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Re: G80 & GT4 for 2004 AWD Astro Conversion

Post by timelessbeing » Thu Apr 25, 2019 2:44 am

forrestmccarthy wrote: 1) Can I use my existing front axles?
You mean if you just swap the rear end? You just need to ensure that the front and rear gear ratios match.
Or you mean put the Blazer front diff into your Astro front axle? You would need to match the spline count of the side gears to your hub.
forrestmccarthy wrote:I can always add a front torsion later on.
Personally I think it's overkill.

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Re: G80 & GT4 for 2004 AWD Astro Conversion

Post by forrestmccarthy » Thu Apr 25, 2019 4:27 am

Yes, put the Blazer front differential in my Astro front axle. At the same time, through a swap or rebuild, I would change my rear gearing to 3.73 as well.
"For the front go to car-parts.com and search for front axle assy. for chevy S-10 Zr2. They all came with 3.73’s. Find one with manual transmission and three button tc and it’s probably a cast iron diff vs. our aluminum. That’s what I did." - Captn. Crunch

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Re: G80 & GT4 for 2004 AWD Astro Conversion

Post by timelessbeing » Thu Apr 25, 2019 5:44 am

It may be possible. You'll have to research it thoroughly first.

What is the output of your front axle? Flange or spline? How many spline? Does it match the Blazer differential?
Setting up gears is no small task. It is a lot of painstaking work (or expensive) with uncommon tools. You're always better off using an assembled axle. You might be able to get away with reusing your axle if you just swap the CV shafts.
I think one of the reasons people swapped the front axle is they could use the disconnect feature and save a bit on fuel consumption.

For a start, have a look at ihatemybike's Astro page. You'll find some useful stuff there.
http://sites.google.com/site/astrosafariworld

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Re: G80 & GT4 for 2004 AWD Astro Conversion

Post by Captn. Crunch » Thu Apr 25, 2019 2:34 pm

forrestmccarthy wrote:Captn. Crunch,

I may have found a unicorn. It's a 2004 Chevy Blazer (89k) with "high wider performance package (opt ZR2), transfer case opt NP1 (3 switch dash control), AT (3.73 ratio, opt GT4)." Looks like I can grab the transfer case from it as well. I still need to do the magnet test. Interestingly, the Blazer front assembly is less expensive and closer than any I could find on an Astro.

A couple questions:

1) Can I use my existing front axles? This would be good as I recently replaced one of the hubs when the ABS quit working.

2) What did you use for a torsion differential in the front of your van? Not sure I'm ready to go this route. Yet, I'm intrigued and considering it. If I have found a unicorn, I can always add a front torsion later on.

FYI: I'm still working on sourcing parts for the rear. Can't find a rear assembly (GT4 & G80) with low mileage anywhere near me. A rebuild might be my best option. If so, I'm considering the Detroit Truetrac, as recommended. It is starting to feel like a winter project as the summer season is upon me and I want to be out adventuring not turning wrenches. Just the same, it would be good to get all the parts lined up.
The front diff will not be cast iron as the doner vehicle was an automatic transmission. I wouldn’t worry a whole lot about that though, the aluminum will hold up fine for 99% of the world. I got one because it was there and so why not.
Front torsen- https://www.ebay.com/itm/MFactory-GMC-S ... 1844126253
Yes you can use the astro front axles. Simply pull out the Blazer units and stuff yours in. You will need to swap over the front prop shaft flange as well. They are not the same.
Find the rear end you want and call them. Ask how much to ship. They ship stuff like that using motor freight all the time
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
np236 transfer case
Torsen equipped cast iron front diff
Torsen equipped rear w/3.73's
2" body lift
S-10 rear leafs
2003 GMC Safari AWD SLT
Stock for now

forrestmccarthy
I am merely driving my van
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How many wheels are on an Astro van? (4): 4

Re: G80 & GT4 for 2004 AWD Astro Conversion

Post by forrestmccarthy » Fri May 24, 2019 5:08 pm

Thanks for all the advice and information. We just returned from Utah were we traveled 300 continues miles of back roads circumnavigating the San Rafeal Swell. This included navigating the Behind the Reef Jeep Trail and fording Muddy Creek. The Astro made a fantastic rolling desert base camp. The trip inspired me to commit to a 4X4 conversion…more on this on my next post.
Attachments
SwellAstro3.jpg
After Fording Muddy Creek
Swell_Astro2.jpg
Camping Behind the Swell
Swell_Astro.jpg
Exploring the San Rafael Swell.

forrestmccarthy
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Re: G80 & GT4 for 2004 AWD Astro Conversion

Post by forrestmccarthy » Fri May 24, 2019 5:52 pm

I’m currently busy with some home improvement projects that I hope will earn me enough kitchen credit for the 4x4 conversion and suspension upgrade this summer. I’ve continued to research my options and sources for parts. Trying to keep the conversion within a reasonable budget, I’ve compiled the following list.

Front Carrier Assembly Replacement
3.73 ratio (opt GT4)

Donor: 2002 Chevy Blazer S10/S15
Front Axle, w/o ZR2; 3.73 ratio (opt GT4)
$200 Marler Auto Supply, Idaho Falls

“Yes you can use the astro front axles. Simply pull out the Blazer units and stuff yours in. You will need to swap over the front prop shaft flange as well. They are not the same. ” – Capt’n Crunch

Transfer Case Assembly Replacement
NP233C: Electric shift 27 Spline input and the 32 Spline rear output rear slip yoke.

Donor: 2004 Chevy Blazer S10/S15
3 switch dash control (opt NP1)
$100 Marler Auto Supply, Idaho Falls

4WD Conversion

$274 Journeys Off Road 4x4 Conversion Kit
https://www.journeysoffroad.com/as4-4conversion.html

Installing the Journeys Off Road 4x4 Conversion Kit
https://www.journeysoffroad.com/swaping ... rcase.html

4WD Indicator Light
$9 Alpinetech PLB12MS 12mm 1/2" 12V LED Metal Signal Indicator Pilot Dash Light (4WD) https://www.amazon.com/dp/B07H8R9GC9/?c ... _lig_dp_it

Rear Differential Rebuild
3.73 (GT4), 10-bolt cover, 28 spline axle 7.6inch ring gear

$565 GM Chevy 7.5" / 7.625" Chevy 10-Bolt Rearend Posi - 28 Spline, Gear, Bearing Kit Package - 3.73 Ratio https://www.amazon.com/dp/B00NT8EQJG/?c ... _lig_dp_it

Leaf Spring Replacement
Measures (A/B) = 26 x 28
1982-1994 Chevy / GMC S10, S15 Sonoma Pickup

“S10 leafs from SD Truck Springs bolt right up and will lift the rear about 4-4 1/2". You'll have to cut or grind about a 1/2" off the center bolt that holds the pack together but other than that it's a direct bolt on.” - H2OJoe

$100 Used Leaf Springs (4/1 Leaves)
Donor: 1993 Chevy Blazer S10/S15 (many other options)
Spring Capacity: 3,500 pounds?
Marler Auto Supply, Idaho Falls

$241 New #22-687 SD Leaf Spring (3/1 Leaves)
Spring Capacity: 2,700 pounds
https://www.sdtrucksprings.com/index.ph ... caf0cefd46

$348 New #22-687 HD Leaf Springs (5/1 Leaves)
Spring Capacity: 3,500 pounds
https://www.truckspring.com/products/tr ... 9fb213ae3e

Sway Bars

$215 Front Hellwig Sway Bar (1 1/8" diameter)
https://www.sdtrucksprings.com/index.ph ... ts_id=3660

$232 Rear Hellwig Sway Bar (3/4" diameter)
https://www.sdtrucksprings.com/index.ph ... ts_id=3659

Skid Plate
DHC Off Road Skid Plates
http://astrosafarivans.org/bb2/viewtopic.php?f=14&t=85

$316 Aluminum Sheet 1/4" x 65.0"x 20.0"
https://www.onlinemetals.com

Extra ~2.75 inches to accommodate air dam/skid plate attachment for Jeep Wrangler bumper

Ball Joints

“The Only other thing I would add to your plan, in order to keep it reliable and good steering, is an upper ball joint re-location. That’s where you take the upper ball joints off, and re-locate them to the bottom sides of the upper a-arms instead of the top sides of the upper A-arms.” - ASV Supporter

While I’ve been unable to find a local source for a cast iron front carrier case assembly, I have found most of the required parts at a salvage yard nearby in Idaho Falls. Please keep in mind my home mechanic skills are limited and my local auto shop will be doing most of the heavy lifting. So labor cost is an important consideration. My price estimates do include shipping.

I could use some advice on few items:
• S10 leaf springs: Can I get by with the less expensive used ones from the salvage yard or is it worth investing new leaf springs? I’m trending to HD (1/4 or 1/5). Currently I have a 4” Overland lift kit with shackles and an added leaf in the rear. However, it is starting to sag. When overlanding I have a lot of weight in the rear including 60 gallons (~500 pounds) of extra water and fuel.
• Sway bars: I’m also experiencing significant sway and planning to install a Hellwig sway bar in the rear. I’m wondering if it’s worth investing in a front Hellwig sway bar as well?
• Yukon Dura Grip: Thoughts? I would prefer to install a Detroit Truetrac but I’m having a hard time justifying the cost.
• If I do decide to install a front torsion later on will the front aluminum carrier assembly be adequate?

Our Astros are amazing little vans and I’m truly impressed by the AstroSafariVans community and what is possible. Thanks for the inspiration and advice!

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Re: G80 & GT4 for 2004 AWD Astro Conversion

Post by Captn. Crunch » Tue May 28, 2019 12:28 pm

Glad your van took good care of you on your latest excursion. Thanks for the pics-looks like an awesome time.
As for which springs, that can be tricky. Used can be fine unless the truck belonged to a landscaper who overloaded the truck and ran it on the bump stops on a daily basis. Odds are you will be fine. HD springs will ride harsh with no load. I put the 2700 lb. in mine and it’s firm bordering on harsh when empty. I don’t mind at all. The firmed up rear springs will probably help with your sway issue as well.
Front and rear sways on the road are always a good thing especially when you’re packing heavy. The S-10 off road crowd who run the same IFS front end we do came up with a quick disconnect for the front sway bar to gain more articulation, but I don’t think you need worry unless you really start to push the limits off-roading. You can put the QD thing on a list of things to do when bored if you want.
I put a Detroit Truetrac in my van. I was running the GM. version previous to the swap and there was nothing wrong with it I just wanted new torsens front and rear. I have the used one in the shed if you want it PM me and it’s yours.
The stock front diff will support the Torsen. The turbo charged Syclone and Typhoon trucks all ran the same aluminum diff so ya it’ll hold up alright. The offroad S-10 guys would pop them on occasion but they were usually running 35’s or 37’s with 4.56 gears in the rocks. You will be fine overlanding. Twin Torsens need to be experienced to be believed. It is AWESOME!!
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
np236 transfer case
Torsen equipped cast iron front diff
Torsen equipped rear w/3.73's
2" body lift
S-10 rear leafs
2003 GMC Safari AWD SLT
Stock for now

forrestmccarthy
I am merely driving my van
I am merely driving my van
Posts: 8
Joined: Wed Apr 10, 2019 12:55 am
antispam: No
How many wheels are on an Astro van? (4): 4

Re: G80 & GT4 for 2004 AWD Astro Conversion

Post by forrestmccarthy » Fri May 31, 2019 1:35 pm

Captn', I' interested in the GM Torsen and sent you private message. Thanks!

Sounds like the S10 HD springs (3,500 pounds) would be overkill and the SD (2,700 pound) can handle the heavy load when overlanding but not to stiff when driving the van in the winter without the rack and overland kit.

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Re: G80 & GT4 for 2004 AWD Astro Conversion

Post by Captn. Crunch » Fri May 31, 2019 4:31 pm

Very cool, I’m sure you will love the Torsen and how mild mannered it is. You’ll probably end up cursing me as you start fixating on “ if one is this good-two must be amazing” process. I’ll rummage around and get back to you ASAP.
The nice thing about the S-10 springs is you gain lift due to the additional curve in the springs over the nearly flat stock AS springs. That extra curvature naturally handles a load better even if the ratings are the same. I’ve carried 1,000 lbs. of mulch behind the rear seat and you could barely notice.
Now for the bad news, I’ve seen pics of where you go exploring in your van and now I know where you live. I’m jealous enough to show up at your front door looking to tag along!
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
np236 transfer case
Torsen equipped cast iron front diff
Torsen equipped rear w/3.73's
2" body lift
S-10 rear leafs
2003 GMC Safari AWD SLT
Stock for now

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timelessbeing
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Re: G80 & GT4 for 2004 AWD Astro Conversion

Post by timelessbeing » Fri May 31, 2019 8:39 pm

Trutrac is the name of the differential I think. Made by Eaton. I don't think GM makes torsen style diffs.

I had HD springs on my Astro and I'm really glad I did. They are much needed in my opinion because the handling is much better. Before I had them the van would wallow all over the place. I only wished there was a way to stiffen up the front.

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Re: G80 & GT4 for 2004 AWD Astro Conversion

Post by Captn. Crunch » Fri May 31, 2019 8:54 pm

timelessbeing wrote:
Fri May 31, 2019 8:39 pm
Trutrac is the name of the differential I think. Made by Eaton. I don't think GM makes torsen style diffs.

I had HD springs on my Astro and I'm really glad I did. They are much needed in my opinion because the handling is much better. Before I had them the van would wallow all over the place. I only wished there was a way to stiffen up the front.
GM put zexel torsen units in firebirds. They did make them

https://www.ebay.com/i/362597192670?chn ... 8mEALw_wcB
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
np236 transfer case
Torsen equipped cast iron front diff
Torsen equipped rear w/3.73's
2" body lift
S-10 rear leafs
2003 GMC Safari AWD SLT
Stock for now

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timelessbeing
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Re: G80 & GT4 for 2004 AWD Astro Conversion

Post by timelessbeing » Sat Jun 01, 2019 8:11 am

Interesting. I had no idea GM equipped them.

Not that the Firebird one is useful to use vanners. It's too small.

But are you sure GM made them. I would think they bought them from JTEKT/Zexel corp.

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Re: G80 & GT4 for 2004 AWD Astro Conversion

Post by Captn. Crunch » Sat Jun 01, 2019 1:38 pm

GM put Torsen carriers in the Camaro and Firebird from 1999-2002 IIRC. You are right that GM did not actually build the units. That was done by either JTEKT or Eaton. Both the Camaro and the Firebird sported the 7.625 rear so we do share carriers with them. The offset and width is different so swapping complete rears is not feasible.
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
np236 transfer case
Torsen equipped cast iron front diff
Torsen equipped rear w/3.73's
2" body lift
S-10 rear leafs
2003 GMC Safari AWD SLT
Stock for now

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