need axle advice

[flomulgator]

So I searched and I searched and now I'm just gonna ask.

My ride is a 1991 V1500 Sub with a corporate 10 bolt, 8.5" axle. The rig is a 6.5TD (actually a 6.5 repower of a 6.2 setup with a Banks turbo, but I digress)

I need to swap out the F&R ring an pinion, because the truck shifts all wonky. I've got a 3.42 gear ratio and 33" tires, and the resulting RPMs are too low. This is causing issues with turbo engagement, which in turn is causing problems with excess heat generation. Also, the transmission has shifting conniptions because the gears are spaced too long. I found that 3.90 gears will get me exactly back to the stock design range for RPMs, but again, I digress.

So I'm about to order my R&P when I start thinking about axles. I've got the 10 bolt on larger tires and a new shiny snail adding 100 torques. May get a tiny lift if I replace the gawdawful springs. May also tow a small weight on rare occasions (<4000#). Is the 10 bolt up to the task long term? If not what should I get? Most importantly, I could not find reliable information on what bolts on to the truck, what requires another part or two, and what requires major modification. Here are some options:

Corporate 12 Bolt
Dana 60
Corporate 14 Bolt
Stuff off old '70s trucks

I've found some good deals on used stuff locally, where I could get either 3 of those with things like disc brakes or a posi/locker already installed, usually in either 3.73 or 4.11 gear ratios. Lot of added bonuses there. I really want a traction device in the rear because I do a lot of highway driving in mixed snow, where 4WD is not practical poor road conditions develop faster than I can reach to the floor.
Side question: Anyone have any experience with an auto locker in the snow?

I only want to purchase something like this though if it's going to be relatively simple. If the 10 bolt is strong enough to last me, I'd prefer to not even bother. Last question: Is it possible to find out the spline count on a 10-bolt without pulling it apart? Cuzidonwana

[More Power]

Aside from changing the R&P ratio, I'd leave the front axle alone. For the rear, the GM 9-1/2" 14-bolt semi floater would be a good choice, and it would allow maintaining the 6-bolt lug axles.

The rear 10.5" GM 8-lug axle wouldn't make sense unless you were planning to use the burb to rock-crawl.

You can read more about the 9-1/2" and an Eaton posi at the following link:
http://www.thedieselpage.com/reviews/randys.htm

Now... The Banks turbocharger is non-wastegated and slow to spool, meaning the real power is in the 2500-3000 rpm range. For those who run at 1800-2000 rpm range looking for mpgs, there are better turbo choices.

Jim

[flomulgator]

Aside from changing the R&P ratio, I'd leave the front axle alone. For the rear, the GM 9-1/2" 14-bolt semi floater would be a good choice, and it would allow maintaining the 6-bolt lug axles.

The rear 10.5" GM 8-lug axle wouldn't make sense unless you were planning to use the burb to rock-crawl.

You can read more about the 9-1/2" and an Eaton posi at the following link:
http://www.thedieselpage.com/reviews/randys.htm

Now... The Banks turbocharger is non-wastegated and slow to spool, meaning the real power is in the 2500-3000 rpm range. For those who run at 1800-2000 rpm range looking for mpgs, there are better turbo choices.

Jim

Yeah, I wasn't planning on messing with the front. I just don't go into 4WD that often, and when I do I'm not railing on it and I'm certainly not towing at speed. Just a gear swap up there.

Thanks for the article. Really I should drive up to Everett and check that place out. Thanks for the suggestion of a 9.5" 14 bolt. Is it a direct swap or what does a swap entail? I'm gathering from your suggestion that the 10 bolt won't cut it for long term durability with a turbo?

I am learning the hard way that Banks could really use a wastegate. Right now my problem is that boost is non-existent unless I'm flooring it, but with the fuel rate turned way up and the RPMs down, my AFR is ugly and my EGTs climb dangerously high. I backed off the fuel a 1/10th of a turn and put in a high-flow T-stat, but the gearing is the real culprit. Just installed a Tiny-Tach (great, BTW) and found my RPMs to be 1600 @ 65mph...way too low for even normal operation. My target is 1800 @ 65mph in OD and 3.90 hits the mark perfectly (which means OE did too). According to your article in 6.2 Vol. II that's the sweet spot for economy and torque, and Banks says that about there is where EGTs should be ~400 deg w/ 2lbs. boost (I'm currently 0.5 # @ 65 mph). From there a downshift will really light up the turbo too.

Gah, too much coffee, too verbose, back on topic. 3.90 is a custom size so if I buy a used axle it will have to be 3.73 (a bit low) or 4.10 (a bit high). With the way my setup works, I'm favoring a bit high. Lots of Dana 60s come that way, and many are available. It appears 14 bolts often come with 3.73. But again, I don't know what kind of work goes into these axle swaps.

[More Power]

Yeah, I wasn't planning on messing with the front. I just don't go into 4WD that often, and when I do I'm not railing on it and I'm certainly not towing at speed. Just a gear swap up there.

Thanks for the article. Really I should drive up to Everett and check that place out. Thanks for the suggestion of a 9.5" 14 bolt. Is it a direct swap or what does a swap entail? I'm gathering from your suggestion that the 10 bolt won't cut it for long term durability with a turbo?

I am learning the hard way that Banks could really use a wastegate. Right now my problem is that boost is non-existent unless I'm flooring it, but with the fuel rate turned way up and the RPMs down, my AFR is ugly and my EGTs climb dangerously high. I backed off the fuel a 1/10th of a turn and put in a high-flow T-stat, but the gearing is the real culprit. Just installed a Tiny-Tach (great, BTW) and found my RPMs to be 1600 @ 65mph...way too low for even normal operation. My target is 1800 @ 65mph in OD and 3.90 hits the mark perfectly (which means OE did too). According to your article in 6.2 Vol. II that's the sweet spot for economy and torque, and Banks says that about there is where EGTs should be ~400 deg w/ 2lbs. boost (I'm currently 0.5 # @ 65 mph). From there a downshift will really light up the turbo too.

Gah, too much coffee, too verbose, back on topic. 3.90 is a custom size so if I buy a used axle it will have to be 3.73 (a bit low) or 4.10 (a bit high). With the way my setup works, I'm favoring a bit high. Lots of Dana 60s come that way, and many are available. It appears 14 bolts often come with 3.73. But again, I don't know what kind of work goes into these axle swaps.

According to Jim Allen's recent book entitled "Differentials", the GM 9.5 appeared in the 1981 in C/K 20/30 pickups, Suburbans and vans - meaning they'll require 8-hole wheels. According to Randy's, 3.23, 3.42, 3.73, 4.10 and 4.56 are the available ratios. These 80's axles would be a bolt-on for your half ton, but the 8-lug thing might be a problem.

Beginning in 1988, GM installed the 9.5 in their 1/2-ton trucks, but the hub to hub width changed, as did the spring perch locations. So... A custom axle might be within the realm of possibility, using a 1981+ 9.5 with custom 6-lug axles.

Now... the GM 10-bolt is stronger than you might think. I put more than 400-hp to one in my Duramax powered 1989 Chevy before swapping in a custom 9.5. I didn't break it even though it was equipped with a posi. Where the 10-bolt falls down is grueling mile after mile under a hard load - like heavy towing. That's partly why current diesel pickups are using an 11.5" AAM rear diff.

I actually spoke to Gale Banks about the slow spooling Sidewinder used in their 6.2 kit. His reply was (and it does make sense) that "power is there when you need it". I suppose this means that a downshift and more fuel will spool the turbo and make the right amount of boost. Unfortunately, tooling around at low rpm and low throttle means there's no or very little boost, and that boost won't rise much till you get a downshift with more pedal.

Gale suggested I try their turbo produced for their 7.3L IDI kit. I would add the Holset HX35W (like that used on the 1994-97 Dodge Cummins) to that recommendation. The Holset is a wastegated turbo that should fit the Banks manifold without a lot of fuss. The factory 6.5 turbo would also be sized about perfectly for the 6.2, but the exhaust outlet won't fit the installation with any grace.

Jim

[flomulgator]

Thank You!
I can't stress enough how valuable information like this is. Possessing only hand tools and limited funds (and knowledge), I don't want to get into custom axle or mount work. But I also wanted to avoid building up an axle with a posi and new parts only to have to throw all that time & $$ away when the axle broke or proved inadequate.

We basically got the turbo for the big grades we encounter out west, especially when we are tooling around the Rockies at altitude. The Banks does a good job of this. Also to be able to pull off passes on 2-lanes around the 5-under drivers that plague Washington's highways. Even fully lit, the turbo only produces < 400 lb/ft so I think even if I was towing something moderate on a grade it wouldn't compare to a Duramax @ 700lb/ft or as you said, heavy towing. Any guidelines on how much weight does start causing problems?

I'll give the bolt-on 80's 14 bolt (w/ wheel swap) some consideration but will likely stay with the 10 bolt. Again, thanks!

turbo geeking tangent:
I think the Banks was styled that way because it gave the biggest possible numbers that look good for marketing. I've got a turbocharged sporty gas car as my DD, so I'm a bit familiar with turbo selection. In the sport world people choose huge turbos that only kick on right near redline (due to very high flow/spooling requirements) but then produce stupendous power. Taken to the extreme, this produces cars known as "dyno queens" cars with turbos so powerful that they are undriveable. They produce 1000hp or whatever on the dyno but going from 150 to 800 hp in the space of 200rpm @ WOT produces uncontrollable wheelspin....so they aren't actually drivable!
Anyways this relates to Banks in that I think they wanted to post some good numbers in a difficult application. So they chose a larger than necessary turbo with a high flow requirement. As you pointed out, a lack of wastegating compounds the issue. There are 3 ways to improve the situation:
1. Smaller turbo. Most non-sporty turbo cars go this route because it is a very driveable setup. Minimal turbo lag, just feels like more cylinders. Some diesels have too (I believe early 12v Cummins and TDI VW's). However, don't post big numbers and run out of breath before the engine does.

2. Sequential turbos (as opposed to twin). One small and one large, best of both worlds. E.G. RX-7, 300zx, etc...

3. Variable Vane Geometry Turbos. Using technology invented by Honeywell for the high-bypass turbofan in aviation, they can change the effective size of the exhaust housing. Pretty cool, very expensive, and currently used by all diesel engines for all makes sold in the US, IIRC.

Anyways, I'm still trying to learn more about wastegating as it applies to flow rates but it clearly has an effect. I read an article that used the banks kit but substituted the Ford IDI Banks turbo like you mentioned for the same reasons. Unfortunately they didn't get into drivability or do much post-analysis after the install. After a long line of other chassis upgrades though I would consider a turbo swap.

/turbo rant

[87max]

From my experience a 14 bolt 10.5 full floater is the only way to go. the semi floaters were known for occasional problems. Go with 4.10's the difference is so minimal it's not worth even doing the math. The beauty of the 14 bolt is they are available in a variety of apps, vans, 2wd, 4wd, 3/4 1ton etc.. check your spring perch location (width) for alignment & find the 14 bolt for you. Detroit lockers are the bomb in that axle you can do it yourself, the carrier gets reused unlike other axles you only replace the spiders and (cross) that's why they are several hundred less for the 14 bolt full floater. Enough savings to buy the axle. I used to run a 14 bolt in the back and a 10 bolt up front. I had 6 lug up front and 8 in the back it's not a crime to do that! I would put about 800 pds in the back and plowed in 2wd most of the time.