Gear ratio

[Gavin]

Hi guys, I have a 2001 gmc sierra 1500 4.8 liter with a stage 2 btr truck cam with the head supporting mods. Other than that it’s pretty much stock with an exhaust. I’m running 33s with 3.73 gears and I can barely get the tires to break lose. I’ve been working with reputable tuner and he says there’s nothing else he can do on his end to help the truck do a burnout. He said that a looser converter or higher gears would help. Just wondering if either the converter or gears would be a better starting point and bang for buck. Or if it would be best to do the converter and gears to reach its full potential. Does anyone have experience on how to get more low end torque out these little 4.8s

 

[ORVietVet]

Why do you want to do a burnout?

 

[Marky Dissod]

01 gmc sierra 1500 4.8L with a stage 2 btr truck cam with the head supporting mods. Other than that pretty much stock with an exhaust.
Running 33" with 3.73 and I can barely get the tires to break lose.

So far, yea, ok, not surprised at all, even if it's a 2WD. 33" tall tires made your truck (NOT your engine) weaker, and 3.73 ain't much to begin with.
4.10 would improve the tow rating for a very good reason. (GM did not offer 4.30 for this truck because they offer stronger trucks.)
Long story short here: 4.30 or 4.56, depending on your NORMAL, PREVALENT usage cases, not your occasional ones.
My guess'd be 4.30 because I don't know your usage case, just statistics. If you use your truck unusually, it could be 4.56 would be better for you.

Been working with reputable tuner and he says there’s nothing else he can do ... He said that a looser converter or higher gears would help.
Just wondering if either the converter or gears would be a better starting point and bang for buck? Would be best to do the converter and gears to reach its full potential?

Don't know anything of the Stage 2 BTR truck cam, but willing to bet more money than I should, that the horsepower peak has moved to a higher RpM than GM OE?
If I remember correctly, the GM OE horsepower peak occurs @ ~ 5200RpM. Where / when does your horsepower peak now?

If this Stage 2 BTR truck cam has moved the horsepower peak past 5200 RpM, then odds are you made your engine more powerful, but NOT any stronger.
In fact it's very likely you made the engine WEAKER under 2500RpM. This seems to go right over far too many people's heads:
Most engines live UNDER 2500RpM for most of their lives, even when driven by leadfoots, even when they play or work too hard, even if they're undersized.
Have not yet found a cam that SHOWS that it makes MORE POWER UNDER 2500RpM on a DYNO GRAPH, even if they can categorically prove it other ways.

For the record, I do NOT recommend a looser converter. It will make your truck less drivable, less sensitive to smaller throttle inputs.
You may find it acceptable, but you WILL notice, and it'll cost you MpG whenever the torque converter is not locked, especially in 1st & 2nd, but even in 3rd & 4th.
Plus you may need to upgrade your ATF cooler one way or another (although this is ALWAYS a good idea regardless).
If you're willing to find a converter that is NOT looser yet has a higher stall RpM than GM OE, it'll be worth the considerable cost, just maybe not to you.

There are only two mods I can almost always recommend to nearly everyone:
*better axle gears - 4.30 (or 4.56, depending on how you usually use it)
*pcm tuning - done thoroughly and properly, it improves longevity and durability, not just the fun stuff cowards are afraid to improve - glad you got this done
The 3rd recommendation, I don't make as often, but I'll make it to you:
*bigger engine, or artificial aspiration - or both, if you've money to burn?

Given what you have now, you'd be PLEASANTLY SURPRISED, if not VERY HAPPY with a 6.0L & 4.10 (or 4.30 or 4.56).
What would you say to someone with a 4.3L Caprice (regardless of what gear was GM OE)? You better say 5.7L & 3.73 ...

 

[Marky Dissod]

33" tires and 3.73 be working against you a lot, lower gear is better ...

Yep. To be clear, the taller the tire, the more gear.
In fact, now that I think about it, if you continue to insist on 33" tires, forget I said 4.10.
Depending on your use cases, 4.30 or 4.56.

... though you'll also get the joy of swapping driveshafts as GM u joints like shedding their straps, u bolt yokes are better.

Again, Yep.

 

[99Sierra2500]

Yep. To be clear, the taller the tire, the more gear.
In fact, now that I think about it, if you continue to insist on 33" tires, forget I said 4.10.
Depending on your use cases, 4.30 or 4.56.

Yeah, 4.56's are best, but that is aftermarket stuff, best find for a junkyard swap will be 4.10's. AFAIK I mean I have heard about 4.56's from the factory, though never seen them in a pickup 14 bolt.

 

[stutaeng]

GMT800 With Threatening Auras v2...

 

[INW-Iron-Steel]

Does anyone have experience on how to get more low end torque out these little 4.8s

Turbo. That's it. The 5.3 and 6.0 have the same stroke length. That is why the 5.3 works OK in a heavy vehicle and the 4.8 is pretty much worthless for doing real work (4.8 van with a trailer is downright pathetic).

In my opinion, you over-cammed the 4.8 for your application. That 212/218 cam shifts the torque curve on a 5.3; the torque loss down low will be worse on the 4.8. If you want to keep that cam and not go forced induction, put a converter in it so you can get into the powerband quicker (2500RPM and up). This comes with drawbacks mentioned above. 4.56s with 33s are a bit much in something you intend to drive regularly. 285/70/17s are 32.7" and I don't consider that a particularly large tire.

If it were me, I'd put a different cam in it. Cheaper and easier than a converter or gears. Take a look at Cam Motion. Their stage 2 cams are much tamer, especially for the 4.8 (202/206 @ .050). The Cam Motion 5.3 stage 1 (200/204) Summit Torkinator (200/205) and BTR Torque (202/202) would be good alternatives that will make low speed torque. With that last one, single pattern cams have a history of being able to make slightly better low speed torque. FWIW, my 4.8 won't spin the 285/60/18s with a limited slip... unless the road is wet.

 

[Marky Dissod]

you over-cammed the 4.8L for your application. That 212/218 cam shifts the torque curve on a 5.3L; the torque loss down low will be even worse on the 4.8L.
If you want to keep that cam and not go forced induction, put a converter in it so you can get into the powerband quicker (2500RPM and up).
This comes with drawbacks mentioned above. 4.56 with 33" are a bit much in something you intend to drive regularly.

It's not an opinion, 4.8L will never have much torque, and you gave up power under 2500RpM for power at higher RpMs.
If you find a converter that will maintain low-throttle drivability AND stall at a higher RpM, you're still never getting any MpGs back.
From stop sign to stop sign / red light to red light, 4.56 with 33" will not be that bad, on the highway you'll lose MpG. Maybe 4.30. You know your environment.

Many GMT800 4.8L Tahoes & Sielvierrados came with 4.10. Swapping an entire axle outright might be less than changing R&P inside the pumpkin, definitely simpler.

 

[JorgeS]

Marky, can you explain what a "looser converter" is? When I read the first place you used that term, I though you meant a higher stall-speed converter; then you said that he needs a converter with a higher stall-speed that is not loose - I'm confused!!
I'm considering a BTR Truck Norris for my Yukon, and I recognize that cruising speed at 70 MPH will require me to spend more time in 3rd gear (70 MPH = 2000 RPM with the 3.42). It's my daily driver, and I rarely run at 70 on the interstate, so I will survive the loss below 2500.
BTW... 33" tires with a 3.73 is the same as stock tires (assuming 265/70R16) with ~3.43 rear end.

 

[Marky Dissod]

Nearly all converters that have a higher stall speed are 'looser', but NOT all of them.

Let's say that you're parallel parking a 220" Suburban in a 232" parking space between two other vehicles with both their drivers dozing off inside.
The looser the converter is, the harder it'll be to successfully get it in there and let both of them sleep.
Even with perfect throttle mgmt, a looser converter will let RpMs climb higher before the vehicle moves (making louder noises of higher pitch).
To oversimplify:
A looser converter wastes more fuel whenever the RpMs are under the converter's stall speed.
A tighter converter acts more like an already engaged physical / dry clutch plate, which is more fuel efficient.
HOWEVER
Stall speed is independent of how loose or tight a converter is.
The converter's internal construction, including its size, can be spec'd and arranged in such a way that maintains GM OE gentle throttle response
AND
have a higher stall speed than GM OE ... but this always costs more because of the specialized construction.

3.73 (or 4.10) will yield more smiles per gallon than a looser converter, lose very little if any highway MpG, and enhance your 4L60E's longevity/durability.
They're not just for improving tow / haul ratings.

 

[99Sierra2500]

OP has not even been back.

Converters are arcane, esp when it's a lockup vs a 3 speed tci streetfighter, yeah ideally cam, converter, and gear all match.

Going off yukon 4.56's

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That is expensive after rebuild, ring and pinion, etc..

4.10's are the easiest. I know running 32.8's, 3.73's, and whatever stock stall, that 4.10's would be better.

 

[INW-Iron-Steel]

Though I have never personally tried it, someone told me years ago the Trailblazer I6 (vortec 4200) converter was a good upgrade for a mild cam pickup. Any thoughts?

 

[99Sierra2500]

I have heard that as well, about the Trailblazer converter. Converters also act differently with lighter vs heavier vehicles; plus the gearing in the transmission as the 4L80E has a tall 1st gear.

 

[Marky Dissod]

Though I have never personally tried it, someone told me years ago the Trailblazer I6 (vortec 4200) converter was a good upgrade for a mild cam pickup. Any thoughts?

If one were to look up the stats for a TrailBlazer 6inline's converter, those stats apply as applied up against a TrailBlazer's 6inline.
If you use a converter spec'd to be mated to a 4.2L 6inline, and instead mate it to a 5.3L V8, its stall speed will go up several hundred RpM.

In other words a converter responds proportionally depending on the engine it's mated to.

 

[CPB]

Time to disable some of the torque management and traction control. Do note these exist to protect the drivetrain from damage. However, it'll help with the burnout goal. The PCM pulls torque during potential wheelspin events by default.

The other thing for burnouts is less traction, so run a worse tire and this will be easier.

There's a few guys with "burnout" tutorials for GMT800 PCM adjustment in VCM editor on YouTube.

 

[AuroraGirl]

So far, yea, ok, not surprised at all, even if it's a 2WD. 33" tall tires made your truck (NOT your engine) weaker, and 3.73 ain't much to begin with.
4.10 would improve the tow rating for a very good reason. (GM did not offer 4.30 for this truck because they offer stronger trucks.)
Long story short here: 4.30 or 4.56, depending on your NORMAL, PREVALENT usage cases, not your occasional ones.
My guess'd be 4.30 because I don't know your usage case, just statistics. If you use your truck unusually, it could be 4.56 would be better for you.

Don't know anything of the Stage 2 BTR truck cam, but willing to bet more money than I should, that the horsepower peak has moved to a higher RpM than GM OE?
If I remember correctly, the GM OE horsepower peak occurs @ ~ 5200RpM. Where / when does your horsepower peak now?

If this Stage 2 BTR truck cam has moved the horsepower peak past 5200 RpM, then odds are you made your engine more powerful, but NOT any stronger.
In fact it's very likely you made the engine WEAKER under 2500RpM. This seems to go right over far too many people's heads:
Most engines live UNDER 2500RpM for most of their lives, even when driven by leadfoots, even when they play or work too hard, even if they're undersized.
Have not yet found a cam that SHOWS that it makes MORE POWER UNDER 2500RpM on a DYNO GRAPH, even if they can categorically prove it other ways.

For the record, I do NOT recommend a looser converter. It will make your truck less drivable, less sensitive to smaller throttle inputs.
You may find it acceptable, but you WILL notice, and it'll cost you MpG whenever the torque converter is not locked, especially in 1st & 2nd, but even in 3rd & 4th.
Plus you may need to upgrade your ATF cooler one way or another (although this is ALWAYS a good idea regardless).
If you're willing to find a converter that is NOT looser yet has a higher stall RpM than GM OE, it'll be worth the considerable cost, just maybe not to you.

There are only two mods I can almost always recommend to nearly everyone:
*better axle gears - 4.30 (or 4.56, depending on how you usually use it)
*pcm tuning - done thoroughly and properly, it improves longevity and durability, not just the fun stuff cowards are afraid to improve - glad you got this done
The 3rd recommendation, I don't make as often, but I'll make it to you:
*bigger engine, or artificial aspiration - or both, if you've money to burn?

Given what you have now, you'd be PLEASANTLY SURPRISED, if not VERY HAPPY with a 6.0L & 4.10 (or 4.30 or 4.56).
What would you say to someone with a 4.3L Caprice (regardless of what gear was GM OE)? You better say 5.7L & 3.73 ...

i feel like youre going to break an axle shaft in a 8.6 10bolt rear with a 4.30 or larger ratio and doing burn outs, maybe im wrong but im suspecting the twisting is gonna strain it

 

[AuroraGirl]

the 4.3 caprice has a 262 cubic inch v8 not the v6

The engine had
200 horsepower at 5000 rpm and 240 lb.-ft. torque at 2400 rpm.

not a screamer but respectible , probably fuel efficient. far cry from the 260 gas/diesel oldsmobile with 110 hp at most or like 85-90 hp for the diesel!!!

 

[Marky Dissod]

the 4.3L caprice has a 262 cubic inch v8 not the v6

From '94-'96, this is true, but before that ...
From '91-'93, the 4.3L LB4 V6 was available for 9C6s and fleet orders.

Drove several LB4 & L99 Caprices as a cabbie, but since I can't prove either of those, here you go:

https://www.impalassforum.com/threads/4-3l-v6-lb4-in-the-92-93-9c6-taxi.738321/post-11884769

AND

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Failed to make clear in this post that the GM Parts Giant VIN being decoded is
1G1BL53Z8PW155788
which is a '93 Caprice 9C6 taxicab with a 4.3L LB4 V6 and a weak@$$ 3.08 (should've been 3.42).

The 4.3L L99 V8 had 200 horsepower @ 5000RpM & 240 ftlb torque @ 2400RpM. not a screamer but respectable, probably fuel efficient.

The L99 4.3L V8 was worth ONE city MpG & ONE highway MpG - ONE! - over the 5.7L LT1. In other words, L99 4.3L V8s were for CAFE MpG reasons.
(Same goes for 2.56, 2.73, 2.93, & 3.08 axles GM wore out many 4L60Es with - 3.23 for real world economy, 3.42 for light fun, 3.73 for serious fun.)
L99 beat the LU2 & L35 in terms of MpG NVH and emissions, and simplified the assembly line, but any respect/praise the L99 deserves won't come from me.
In the real world, the 4.3L L99 V8 is inferior in every measurable and unmeasurable way to any 5.7 LT1 in decent running condition. (I tune L99s & LT1s by the way.)
If you buy an L99 Caprice, I promise you, even if the L99 needs no repairs or maintenance, but especially if you want any hint of performance at all, PLEASE,
install a 5.7L LT1, tune the pcm for it (I can, if you like?), buy an 8.5" 10-bolt if it needs it, 3.42 for highway, 3.73 for city stop'n'go & more fun stuff,
then suspension and steering to your taste.

 

[JorgeS]

The 4.3L V6 was also cheaper: 2 fewer pistons, con-rods, less iron, less steel, etc. and a little lighter. CAFE drove manufacturers to do stupid/crazy stuff to reduce weight and other items.
One thing I never understood was how many police Caprices, used by. Iti departments were made with the 4.3L V8. Maybe they wanted to slow them down.
I can't imagine a 4.3L V8 would cost less, nor weigh less than a 5.7

 

[Marky Dissod]

The 4.3L V6 was also cheaper: 2 fewer pistons, con-rods, less iron, less steel, etc. and a little lighter.
CAFE drove manufacturers to do stupid/crazy stuff to reduce weight and other items.
One thing I never understood was how many police Caprices, used by Iti departments were made with the 4.3L V8. Maybe they wanted to slow them down.
I can't imagine a 4.3L V8 would cost less, nor weigh less than a 5.7L

The 4.3L V6 itself was cheaper, but GM apparently thought that it'd be cheaper to make an externally identical V8 to an LT1,
maybe so that the LT1 wiring & pcm & various lines and stuff became perfectly redundant, to simplify and speed up the assembly line?

Like I said, though, the L99 was better than the 4.3L V6s (LU2 & L35) in terms of MpGs, emissions, and Noise / Vibrations / Harshness,
which are more important to GM's target demographic (mid-50s & older) than power and torque.
And yes, the 4.3L L99 weighed more than the 5.7L LT1 - 4.3L iron block was heavier by enough to outweigh the 4.3L's lighter bottom end parts.
A 4.3L V6 would've been better for 2nd 3rd and 4th owners, but GM was selling to Aunt Cester & Aunt Tique, who definitely preferred the L99 vs the LU3/L35.
FYI, the 5.7L LT1 outsold the 4.3L L99 just under 2-to-1 for police depts (9C1s), but the Roadmaster (5.7L) & Fleetwood(5.7L) sales kept it just over 50/50.
In other words, a majority of Caprice sedans came with L99s (and 2.73 or 2.93 axles instead of 3.23),
which made wagons Roadmasters & Fleetwoods more popular in the 2ndhand markets, despite their 2.56 or 2.93 axles.

CAFE is dumb. After how many decades of undergearing (?), compare the 4L60's gearing to the 6L80 / 8L90 / 10L80:
10L80 . . . . . 8L90 . . . . . 6L80 . . . . . 4L60E
4.70 . . . . . . 4.56 . . . . . 4.03
2.99 . . . . . . 2.97 . . . . . . . . . . . . . . . 3.06
2.15 . . . . . . 2.08 . . . . . 2.36 . . . . . . . . . .
1.77 . . . . . . 1.69 . . . . . . . . . . . . . . . 1.63
1.52 . . . . . . . . . . . . . . . 1.53 . . . . . . . . . .
1.28 . . . . . . 1.27 . . . . . 1.15 . . . . . . . . . .
1.00 . . . . . . 1.00 . . . . . . . . . . . . . . . 1.00
0.85 . . . . . . 0.85 . . . . . 0.85 . . . . . . . . . .
0.69 . . . . . . . . . . . . . . . 0.67 . . . . . . 0.70
0.64 . . . . . . 0.65

In other words, GM used MORE gears AND ALSO shorter gearing to improve city MpG. Highway MpG was improved moreso by other stuff than by gearing.
This is why, in the real world, GMT800s should all have 3.73 or 4.10 axles minimum (more if the tires are over 31.6" tall).