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96-99 7.4 performance mods
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That is some great advice and all the mods mentioned i will be doing from the start.

96' L29 454 engine.
ZZ502 cam and upgraded valvetrain
Comp 1.72 roller tip rockers
Hedman 1 3/4 LT's with 3" HF Cats and full 3" dual exhaust with an x-pipe muffler and dual 3" tailpipes.
Under drive crank pulley (43%)
Custom tuned 0411 swap
Volant CAI
07+ EFans
MSD Digital 6A Ignition Box and Coil
Billet aluminum distributor, new stock Iridium plugs and new wires.

These will be done for sure along with an HD2 shift kit in the 80e and a 2500 stall converter.

Have been looking at doing a larger 90mm LS TB swap but still researching it. I have also been thinking about having some plenum spacers made to allow the use of tall VC's but that may run into hood clearance issues, so that is on the back burner for now.

Im hoping that once its all together and tuned and in my Tahoe Limited i can see in the ~400HP/450+TQ at the rear wheels, but that may be alittle ambitious. Once it's running/driving with the BBC, I'm going to be doing a 9.5 14 bolt swap so i don't have to worry about the stock 8.5 blowing up!

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I might get some flame for this, but I'm going to give you some realistic experience-based advice on that rear end before you make that decision.
Tahoe Limiteds all come with 3.42:1 gears and the G80 locking differential. The weak point of that rear end is the G80 differential. Even a 9.5" will be weak if it has a G80. That being said, it's reasonable to suggest replacing the differential in the 9.5 if you get one, but what about the 8.5?

Consider this: the 3.42:1 gearing in your 10-bolt 8.5" is inherently stronger than a 3.73:1 gearset and especially stronger than a 4.10:1 set because it has greater pinion to ring gear contact. The gear ratio also reduces the torque the differential and axle shafts see. An 8.5" with a good limited-slip aftermarket differential (Eaton Posi) and a cast aluminum cover (for increased housing rigidity) will hold up to and even somewhat beyond the power levels you're targeting.

As far as torque, under a Tahoe you'll get wheelspin before you'll get a broken axle shaft. That's of course as long as you don't intend to put slicks or drag radials on it. If you do then the 10-bolt will not work for this.

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James B. wrote:
I might get some flame for this, but I'm going to give you some realistic experience-based advice on that rear end before you make that decision.
Tahoe Limiteds all come with 3.42:1 gears and the G80 locking differential. The weak point of that rear end is the G80 differential. Even a 9.5" will be weak if it has a G80. That being said, it's reasonable to suggest replacing the differential in the 9.5 if you get one, but what about the 8.5?

Consider this: the 3.42:1 gearing in your 10-bolt 8.5" is inherently stronger than a 3.73:1 gearset and especially stronger than a 4.10:1 set because it has greater pinion to ring gear contact. The gear ratio also reduces the torque the differential and axle shafts see. An 8.5" with a good limited-slip aftermarket differential (Eaton Posi) and a cast aluminum cover (for increased housing rigidity) will hold up to and even somewhat beyond the power levels you're targeting.

As far as torque, under a Tahoe you'll get wheelspin before you'll get a broken axle shaft. That's of course as long as you don't intend to put slicks or drag radials on it. If you do then the 10-bolt will not work for this.


Are you kidding? Who in his right mind is going to flame you sir? hehe

You had mentioned this in the past and it does make sense, but as long as one would stick within the highest numerical ratio available on the 10 bolt and the OEM tire size for that given ratio, I would assume the diff would survive as traction is the weak link in the chain until sticky tires are added or taller ones.

As previously mentioned:




Quote:
I realize many of my opions are unpopular with a lot of people, but I do try to view things across a very broad spectrum.

There are a few reasons that the TH400 was built with a narrow range of gear ratio. First, this transmission was built to handle the torque produced by GM's strongest engines of the day. The narrow the range of ratios is in the trans the closer the ratios can be to each other. The less engine RPM change between rotating component during a shift the more torque the same clutch pack can handle if it were shifting a wider ratio. Clutch packs are sized to handle the specified torque at the desired shift softness without overheating. Increasing shift firmness or narrowing the ratios between gear increases the amount of torque that clutch will handle. Second, the close ratios make the TH400 and 4L80-E ideal for the 6.2 and 6.5L Diesel and Turbo-Diesel since they have a much narrower RPM range than gas engines.

I personally love the ratios in the 4L80-E because they're close together and the engine never falls out of it's torque band even with a stock converter. My experience with them is a little bit biased because I have 4.56 gears for strong launches and a Gear Vendors Overdrive to give me a wider overall range. I only use the GV on the freeway over 60MPH, but without it I'd have to be running 3.73 or 3.42 gears in the back because highway engine RPM is too high at anything over 60mph.

Changing the ratios in the 80 will increase the amount of work the clutches have to do, that can be easily compensated for with additional line pressure in programming or by enlarging the feed holes in the valve body. The 4L80-E has the advantage of NOT being overworked in stock trim where as the 4L60-E is grotesquely inadequate for most of the stock vehicles it's installed into.

As for this discussion on torque handling and gear ratios, some of the things stated are the opposite of what is true. Given two shafts, one driven by the other through gearing (for example axle and pinion, or output shaft and input shaft) any time you increase the gear ratio you are increasing the amount of torque the driven shaft has to deal with. In the case of a rear end, the ring gear has to transfer power through the differential to the axles. The differential and its lock-up or limited slip mechanism will have to deal with increased torque from the increased gearing. For this reason and because tooth contact takes place over a wider collective surface area between the ring and pinion, 3.42 gears would survive MUCH higher torque loads than 4.10 gears would, always.

-James


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Well even with the 9.5 i was going to go with 3.42 gear. So maybe ill just upgrade my stock 8.5 with a true Trac and some new bearings and the aluminum diff cover and call it a day.

I found a deal on a 6 lug 9.5 for 150 bucks but if needed i can always do the swap down the road.

And I'd never flame, i love the knowledge without the b.s. this forum provides!

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Flaming James B. It just isn't done. Besides, you've all missed the biggest reason why we listen to James B.



He clearly knows what he's doing.

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Speeder wrote:
Flaming James B. It just isn't done. Besides, you've all missed the biggest reason why we listen to James B.



He clearly knows what he's doing.


He definitely has my respect!

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That's not even the best pic but I couldn't find the one from the track when he had the driver side front over a foot off the ground. It's around here somewhere.

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I like this thread

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I miss driving that truck. It's time to build a better one.

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James B. wrote:
I miss driving that truck. It's time to build a better one.


Share the details on that Tahoe please? And also if you were to do it again what would you do differently?

Also, i listed my initial build plan a few responses up, anything you would change or?

Thanks

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At the time of that picture it still had a built 4L60-E in it with a 3200 RPM 10.5" converter and Gear Vendors overdrive. The rear end was already a 10.5" 14-bolt with an Eaton Posi and 4.56:1 gears. The motor at that time was still the stock bottom-end L31 with Edelbrock E-tec 200 heads, 1.6:1 roller rockers, and a Crower 00401LM cam. The Whipple at the time was still the 1.6L non-intercooled unit the kits came with, and it had a 2.5" pulley on it making nine pounds of boost with water injection. Whipple's own auxiliary injection system still provided the extra fuel but with upgraded 62# injectors instead of the 42# ones it came with. Exhaust was through a pair of TOG headers at that time through dual 3" exhaust.

The fastest it ever evolved to was based on a GM HT383 shortbock. Same heads, same cam, then Hooker long tubes, Marine intake with 62# injectors, Whippletronics delete, water injection deleted, water cooled intercooler and 2.3L Whipple making 10psi, built 4L80-E with high stall converter, and the ability to tune it to a 2-BAR MAP sensor with TunerCATs. It was feloniously fast right up until the moment the crank broke.

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I'd be all over that 14 bolt. 10 bolts are junk IMO. I have more 10 bolts come in with bad pinion bearings and stock trucks than anything out there. But that's just my .02

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James B. wrote:
At the time of that picture it still had a built 4L60-E in it with a 3200 RPM 10.5" converter and Gear Vendors overdrive. The rear end was already a 10.5" 14-bolt with an Eaton Posi and 4.56:1 gears. The motor at that time was still the stock bottom-end L31 with Edelbrock E-tec 200 heads, 1.6:1 roller rockers, and a Crower 00401LM cam. The Whipple at the time was still the 1.6L non-intercooled unit the kits came with, and it had a 2.5" pulley on it making nine pounds of boost with water injection. Whipple's own auxiliary injection system still provided the extra fuel but with upgraded 62# injectors instead of the 42# ones it came with. Exhaust was through a pair of TOG headers at that time through dual 3" exhaust.

The fastest it ever evolved to was based on a GM HT383 shortbock. Same heads, same cam, then Hooker long tubes, Marine intake with 62# injectors, Whippletronics delete, water injection deleted, water cooled intercooler and 2.3L Whipple making 10psi, built 4L80-E with high stall converter, and the ability to tune it to a 2-BAR MAP sensor with TunerCATs. It was feloniously fast right up until the moment the crank broke.


Sounds like a fun ride for sure! Im getting super stoked about this 454 swap, cant wait to fell that big block torque!

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James B. wrote:
At the time of that picture it still had a built 4L60-E in it with a 3200 RPM 10.5" converter and Gear Vendors overdrive. The rear end was already a 10.5" 14-bolt with an Eaton Posi and 4.56:1 gears. The motor at that time was still the stock bottom-end L31 with Edelbrock E-tec 200 heads, 1.6:1 roller rockers, and a Crower 00401LM cam. The Whipple at the time was still the 1.6L non-intercooled unit the kits came with, and it had a 2.5" pulley on it making nine pounds of boost with water injection. Whipple's own auxiliary injection system still provided the extra fuel but with upgraded 62# injectors instead of the 42# ones it came with. Exhaust was through a pair of TOG headers at that time through dual 3" exhaust.

The fastest it ever evolved to was based on a GM HT383 shortbock. Same heads, same cam, then Hooker long tubes, Marine intake with 62# injectors, Whippletronics delete, water injection deleted, water cooled intercooler and 2.3L Whipple making 10psi, built 4L80-E with high stall converter, and the ability to tune it to a 2-BAR MAP sensor with TunerCATs. It was feloniously fast right up until the moment the crank broke.


Wish mine was that fast but then again I'm only 6 psi and at 4500 feet. Need an intercooler to and some traction

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If I did it differently I would spend a penny trying to make a classic smallbock fast. It would either be a bigblock or a Gen-3/4 smallbock with boost. I have a huge investment in Big Block stuff already and would lean that direction with what's already on hand, however if I were starting from scratch with nothing it would be a 6.0L block-based build with L92 heads.

The rear end I would do differently entirely. I tried two different types of conversions to non-float. Both sucked in their own ways with different weaknesses. The way I'd go next time would be to convert a 10.5 to 6 lug with aftermarket hubs and disc brakes leaving it full-float. In this setup you have to machining out the center of the wheels to clear the hub but it leaves enough meat to be safe. 5-lugs not an option doing this. (6-lug rotors from a heavy half ton are dimensionally identical to 5-lug stock rotors, just with 6*5.5" pattern.). The other option is a 9.5" rear end. Easily strong enough, I just hate C-clips. Would need axle shafts and drums spec'd for a 90-92 C1500 454SS pickup to keep it 5-Lug. Don't even bother trying to find a complete 5-lug 9.5 - they are exceedingly rare. If you do stumble upon one then you should also play Lotto.

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Some inspiration:
http://bertok.us/pics/0-120.mpg

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James B. wrote:
I just hate C-clips. .


https://youtu.be/xy9YlToXuUY

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CrazyHoe wrote:
James B. wrote:
I just hate C-clips. .


https://youtu.be/xy9YlToXuUY


That's awesome

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James B. wrote:
I miss driving that truck. It's time to build a better one.


Whipple makes nice systems for the LSX

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James B. wrote:

Consider this: the 3.42:1 gearing in your 10-bolt 8.5" is inherently stronger than a 3.73:1 gearset and especially stronger than a 4.10:1 set because it has greater pinion to ring gear contact. The gear ratio also reduces the torque the differential and axle shafts see. An 8.5" with a good limited-slip aftermarket differential (Eaton Posi) and a cast aluminum cover (for increased housing rigidity) will hold up to and even somewhat beyond the power levels you're targeting.

As far as torque, under a Tahoe you'll get wheelspin before you'll get a broken axle shaft. That's of course as long as you don't intend to put slicks or drag radials on it. If you do then the 10-bolt will not work for this.


The internet racers comment often on how the 8.5" comes close to the 12" in strength.

I have a few concepts I want to explore on this subject in a different tread...

Food for thought:

http://www.crawlpedia.com/thick_gears.htm


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