10 bolt upgrades ("big" 8.5", 30 spline, w/big axle shafts and big wheel bearings)

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Horntoad

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I know a lot of people think (some quite vehemently, including @Schurkey :)) the 10 bolt is crap. But I also know many who think it, at least the big 8.5" 10 bolt with 30 splines and big 1.32" shafts (which are not necked down at the splines like the 1.28", correct?) and big bearings, is a good stock axle with limitations.

As I understand it, the weaknesses to address might be stronger axle shafts (not prob necessary with an open diff), carrier bearing cap support bolts via an aftermarket diff cover (and which also strengthens the housing), and the G80 (which I don't have - to the best of my knowledge is sort of a locker/limited slip hybrid; and even with the G80 I hear mixed reviews and that often instances of them blowing up are due to abuse).

I know many will say swap in a 14-bolt, but that axle is twice as heavy or more. I don't know that I need it; mine is not a full-time 4WD rig, and I'm not doing any rock crawling.

So I'm thinking a(n Eaton/Detroit) True-Trac limited-slip and 1541 axles with new wheel studs (maybe Richmond/Excel or USA Standard Gear, as they've got them on RockAuto), not sure which bearing cap support diff cover yet. Timken bearings and races (are they the only way to go or is that some hype?; carrier bearings would need to fit the True-Trac carrier; see also), and seals (brand recommendations?).

Anything I'm missing? Suggestions, insight, and constructive comments welcome, as are parts suppliers and cost saving tips.

This is a 1995 Tahoe 4WD 2DR 5.7L w/3.42 gears. Thanks for reading! (and I've already got 11" duo-servo rear drums I need to install; which is partly why I'm thinking if I've got to pull the axle shafts to install those, what else should I do while I'm at it)
 
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Erik the Awful

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If you're sticking with a 10-bolt and want it to survive, the weight of your wheels and tires is important. The overall weight of your rig is also important. Most important is your driving style.

Use a solid pinion spacer instead of a crush sleeve. Replace the factory bearing cap bolts with ARPs. Consider c-clip eliminators.
 

RichLo

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If your putting that much work into it, weld the axle tubes to the diff housing also...

 

Schurkey

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I know a lot of people think (some quite vehemently, including @Schurkey :)) the 10 bolt is crap.
[Ted Cassidy Voice] You rang? [/Ted Cassidy Voice]

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The 10-bolt is not crap...when used as intended by the folks who designed it. It's a significant upgrade from the previous 8.2" axle. The 8.5" was used on small-block powered compact and intermediate cars with substantial success. I've got one under a '77 Nova that I intend to keep. Note that I also intend to put an aftermarket differential case in the thing to lose the one-wheel peel.

The problem with the 8.5" 10-bolt is GM thinking it's suitable for a full-size truck. They never put it in a full-size CAR until "full size" cars were downsized to "intermediate" size and weight.

IF (big IF) you use your Tahoe like a car--lightly loaded, rarely stressed--the 8.5 may last the life of the vehicle. If you use your Tahoe like a truck, the differential is at risk of blowing up. GM did upgrade the axle shafts/bearings but so far as I know, they weren't the real weakness.

But I also know many who think it, at least the big 8.5" 10 bolt with 30 splines and big 1.32" shafts (which are not necked down at the splines like the 1.28", correct?) and big bearings, is a good stock axle with limitations.

As I understand it, the weaknesses to address might be stronger axle shafts (not prob necessary with an open diff), carrier bearing cap support bolts via an aftermarket diff cover (and which also strengthens the housing), and the G80 (which I don't have - to the best of my knowledge is sort of a locker/limited slip hybrid; and even with the G80 I hear mixed reviews and that often instances of them blowing up are due to abuse).

I know many will say swap in a 14-bolt, but that axle is twice as heavy or more. I don't know that I need it; mine is not a full-time 4WD rig, and I'm not doing any rock crawling.

So I'm thinking a(n Eaton/Detroit) True-Trac limited-slip and 1541 axles with new wheel studs (maybe Richmond/Excel or USA Standard Gear, as they've got them on RockAuto), not sure which bearing cap support diff cover yet. Timken bearings and races (are they the only way to go or is that some hype?; carrier bearings would need to fit the True-Trac carrier; see also), and seals (brand recommendations?).

Anything I'm missing? Suggestions, insight, and constructive comments welcome, as are parts suppliers and cost saving tips.

This is a 1995 Tahoe 4WD 2DR 5.7L w/3.42 gears. Thanks for reading! (and I've already got 11" duo-servo rear drums I need to install; which is partly why I'm thinking if I've got to pull the axle shafts to install those, what else should I do while I'm at it)
Kennythewelder rebuilt his 8.5" and seems entirely satisfied with it. Given that 3.42-geared 9.5" axles are somewhat rare, maybe rebuilding your 8.5 is worthwhile in your case, especially considering that you already own the 11.x brakes waiting to be installed, and the aftermarket differential is likely stronger than the OEM diff.

When it was me, I went with the 9.5" axle. Took two years and a trip to The Big City (~800 mile round-trip) to get the only 3.42/G80 K2500 unit I could find. The 8.5" axle I took out, went into my friend's '89 K1500 when his 8.5" differential exploded. My 8.5" was a sloppy, worn-out mess then, but it's still soldiering on in his truck. Fortunately, he probably hasn't put 500 miles on that truck in the last three years.

If you had 3.73 gears, a 9.5 would likely be easier to find, and I wouldn't suggest keeping the 8.5" at all.
 
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Horntoad

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As I thought and read more about the 8.5" 10-bolt, I started to wonder if upsizing to the 11" rear drums was just putting more strain (weight) on the already limited-duty/medium-duty axle. I partly don't want to go the 14 bolt because it's (allegedly) much heavier; at least part of that additional weight is the typically bigger rear drums. Upsizing to larger drums or the 14 bolt means more unsprung weight. Larger drums on the 10 bolt also means more levered weight straining where the axle tubes connect to the housing. I purchased the larger drums versus going with a disc conversion because of the complexity, parking brake considerations, and additional cost (at least for aftermarket) of a disc brake conversion, because I believe that drum brakes aren't as bad/disadvantaged as the echo chamber tends to believe, and because I could use off-the-shelf parts (calipers, drums, master cylinder, etc.) that were engineered by GM to be used together on versions of this truck, which @Schurkey it seems we both appreciate that.

A few questions.

1. How much more do the 11" drums weigh than the 10" drums?
2. Can you covert to 6-lug rear discs using predominately off-the-shelf parts (other than maybe the caliper bracket)?
3. How much weight would appropriately sized rear discs save me over the 11" drums? What size rotors would be equivalent to 11" drums?
4. Having just installed the 1.25" bore non-quick-uptake master cylinder, if I went with rear discs would I need to consider getting a different one that was designed for disc/disc and a different proportioning valve?

5. How much should I even be worrying about the extra weight of the 11" drums on the 10-bolt? I admittedly can sometimes overthink things, but it also a lot of the time tends to lead to me getting it right the first time.

As I was writing the post I continued to research, so I'll attempt an answer for a few of my own questions.

1. Several sites list the 11" 18B275 drum at 25 lbs each and the 10" 18B202 at 19.8 lbs each. So upsizing from 10" to 11" drums adds about 10 lbs. Doesn't seem like much.
2. Apparently yes.
3. Several sites list the 11.6" 18A258SD front rotors at 16 lbs each. That would be a weight savings of 18 lbs over the 11" drums. But several sites have the 18FR746C caliper at 11 lbs. So that is no savings at all (of course I didn't add up the pads, shoes, hardware, but negligible compared the the rest). Would a smaller rear rotor be possible (rarely are front and rear brakes the same size)?

And while *I'm no brake engineer* (I do enjoy trying to calculate stuff somewhat logically), if the front rotors are 11.6" (with a 1.9" pad contact surface; an 11.6" outer rotor diameter and thus a 9.57" inner rotor diameter; using pi*r^2 the difference of the inner and outer areas, the swept area, is about 31.7 sq in,) and assuming a 70/30 braking split would we only need (about 13.6 sq in of swept area for the rear, which if the inner rotor diameter were the same, 9.57", that would mean) a 10.5" rear rotor? I don't know the rear axle flange diameter (it looks from pictures to maybe be around 7.35") but if a smaller inner rotor diameter were possible then that would be a bit lighter disc rotor.

5. So perhaps I don't (nor do you) really need to worry too much about the added weight of the 11" drums. (somewhere I saw someone say the bigger drums were like 100 lbs of the extra weigh of the 14 bolt).

Insight, experiences, and pointing out things I missed are all appreciated.
 
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HotWheelsBurban

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I haven't scaled them, but I can most assuredly vouch that the 8 lug, 13" x 2 1/2" drums are very heavy! Just guessing I'd say 50# each or more, and that is just the bare drum.
These are for the 14 bolt full floating axle in my 3500 CCLB, spare drums I got from another local member last year.
 

Erik the Awful

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I started to wonder if upsizing to the 11" rear drums was just putting more strain (weight) on the already limited-duty/medium-duty axle.
The drums would only put strain on the axle flange where the wheel bolts. Unless you're power stalling it, it's not in conflict with the axle shaft.

If you're using your truck for trucky stuff, you're overthinking it. The stock 10" drums work fine, if a bit weak on braking power. The 11" drums are a great upgrade and you won't notice the difference until you step on the brakes. Discs don't have any more stopping power, but they're easier to maintain.

If you're trying to build a road racing truck, you want the biggest brake kit, front and rear, that you can stuff in there. Budget about $3000-$5000.
 

Horntoad

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If you're sticking with a 10-bolt and want it to survive, the weight of your wheels and tires is important.

The drums would only put strain on the axle flange where the wheel bolts. Unless you're power stalling it, it's not in conflict with the axle shaft.
(Understanding the 10" to 11" drums aren't much of a weight different) why is the weight of the wheels and tires important, but the weight of the drums is not? Because (semi-float) wheels and tires are bolted to the axle shaft (flange) whereas the drums bolted to the axle tube (flange)?
 

shovelbill

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(Understanding the 10" to 11" drums aren't much of a weight different) why is the weight of the wheels and tires important, but the weight of the drums is not? Because (semi-float) wheels and tires are bolted to the axle shaft (flange) whereas the drums bolted to the axle tube (flange)?
Rolling resistance...
 
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