Chevy awd van front diff
- Thread starter BigDan
- Start date
Herbie
Rendezvous Conspirator
GM Vans have the GM 7.25" IFS front diff. Smaller than the trucks, and definitely not a Dana part. Yes, AFAIK, the 1500AWD and very rare 2500AWD have the same running gear.
Not a particularly sturdy part, but you have to ask yourself what your use case is. If you're going to take a big tall van and put it in a very technical terrain where you're likely to be lifting a wheel, etc., then it could be a problem. If you're building something for FS roads and the like, though, then you should be fine as long as a little mechanical empathy is used. Swapping out the transfer case for one with a low range makes the biggest difference, since you can really slow down and crawl along in 4Low. (Luckily this is cheap and easy.)
I had essentially the same diff in my overloaded Astro van (along with the tiny 7-5/8" GM rear diff) and did fine with FS roads and the occasional technical terrain - as I said, having a 2-speed transfer case with 4Low is what really made the biggest difference for me. (NP233 in my case, but I now a couple of people here on ExPo did a similar 2-speed swap on their Express/Savanna vans)
If you absolutely HAVE to have the toughest parts that will bolt into the van, there are some Iron-housing front differentials in some of the older Blazer ZR2 models. A couple of the hardcore offroading Astro/Safari guys managed to find these in junkyards and build them up as a replacement for the weaker aluminum-housed OEM units in the vans. A deep dive into the archives at https://chevygmcvans.com/ might yield more info.
Not a particularly sturdy part, but you have to ask yourself what your use case is. If you're going to take a big tall van and put it in a very technical terrain where you're likely to be lifting a wheel, etc., then it could be a problem. If you're building something for FS roads and the like, though, then you should be fine as long as a little mechanical empathy is used. Swapping out the transfer case for one with a low range makes the biggest difference, since you can really slow down and crawl along in 4Low. (Luckily this is cheap and easy.)
I had essentially the same diff in my overloaded Astro van (along with the tiny 7-5/8" GM rear diff) and did fine with FS roads and the occasional technical terrain - as I said, having a 2-speed transfer case with 4Low is what really made the biggest difference for me. (NP233 in my case, but I now a couple of people here on ExPo did a similar 2-speed swap on their Express/Savanna vans)
If you absolutely HAVE to have the toughest parts that will bolt into the van, there are some Iron-housing front differentials in some of the older Blazer ZR2 models. A couple of the hardcore offroading Astro/Safari guys managed to find these in junkyards and build them up as a replacement for the weaker aluminum-housed OEM units in the vans. A deep dive into the archives at https://chevygmcvans.com/ might yield more info.
Herbie
Rendezvous Conspirator
I think 3.42:1 and 3.73:1 are the most common, but I had regeared both ends of my van to 4.11:1 and was very happy.
(I've also seen 3.23s in some yards, and certainly if you're regearing with new parts, then everything from 3.08 to 4.56 can be had)
The biggest bummer is that there aren't a lot of great choices for lockers, etc. in any of the smaller GM applications. (No air or e-lockers for the 7.25 or 7.625 diffs, AFAIK.) The GM G80 can be had in yards, but is a so-so locking solution. There are a couple of Detroit or lunchbox style lockers for the rear, and I think there is ONE torsen style LSD for the front diff, but probably only worth it if you find a cast-iron case to put it in. But again, I was fine for 10 years with open diffs and a 2-speed x-fer case.
BigDan
Observer
Am I ready to regear ? NopeI think 3.42:1 and 3.73:1 are the most common, but I had regeared both ends of my van to 4.11:1 and was very happy.
(I've also seen 3.23s in some yards, and certainly if you're regearing with new parts, then everything from 3.08 to 4.56 can be had)
The biggest bummer is that there aren't a lot of great choices for lockers, etc. in any of the smaller GM applications. (No air or e-lockers for the 7.25 or 7.625 diffs, AFAIK.) The GM G80 can be had in yards, but is a so-so locking solution. There are a couple of Detroit or lunchbox style lockers for the rear, and I think there is ONE torsen style LSD for the front diff, but probably only worth it if you find a cast-iron case to put it in. But again, I was fine for 10 years with open diffs and a 2-speed x-fer case.
I did both jeeps + lockers ,enough money spent
Ill try to find one with 3:73 , maybe a small lft ,and a 2 speed t/c
Thank you so much for the advices
Scotty D
Active member
These vans are really geared for getting good fuel economy in a big van. The transmission is fairly light duty and the rear end on mine is geared way to high
That said I have gone all over Baja for years on roads thats many people with true 4x4 shied away from
I suggest keeping towing to a minimum
That said I have gone all over Baja for years on roads thats many people with true 4x4 shied away from
I suggest keeping towing to a minimum
Herbie
Rendezvous Conspirator
Agreed - gearing change only really necessary if you're adding a lot of tire, etc.
My Astro (again, smaller, but analogous running gear) left the factory with 3.42s and a 215/70-16 (under 28") tire. For the places I wanted to go, I went up to ~30" tire and added a lot of weight with the pop-top and camper build. At that point, the 3.42 gears were showing how tall they were. If I'd had 3.73s, I probably would have been fine. I went 4.11s because I could, and thought more tire might be on the way. By the time I sold the van, I was happy with 4.11s because the shorter gearing made hillclimbs easier and I was never going to run top-speed on the highway due to the poor aerodynamics.
My Astro (again, smaller, but analogous running gear) left the factory with 3.42s and a 215/70-16 (under 28") tire. For the places I wanted to go, I went up to ~30" tire and added a lot of weight with the pop-top and camper build. At that point, the 3.42 gears were showing how tall they were. If I'd had 3.73s, I probably would have been fine. I went 4.11s because I could, and thought more tire might be on the way. By the time I sold the van, I was happy with 4.11s because the shorter gearing made hillclimbs easier and I was never going to run top-speed on the highway due to the poor aerodynamics.
