"Double down or fold" - Part 2 ...

[Martinjmpr]

@Martinjmpr don't forget that if you go with a gear swap, you've got to do both axles.

Yeah, I think the $850 that Tom (ExplorerTom) quoted was for both.

What's the next ratio up? 4.10 or 4.11? Was that ratio ever offered from the factory?

Also, how would I get my speedo and odometer recalibrated? Can that be done with a computer?

 

[Todd780]

Yeah, I think the $850 that Tom (ExplorerTom) quoted was for both.

What's the next ratio up? 4.10 or 4.11? Was that ratio ever offered from the factory?

Also, how would I get my speedo and odometer recalibrated? Can that be done with a computer?

4:10's were. I had them in a 2000 Suburban 1500.

 

[ExplorerTom]

Yes- it’s for both axles.

And the gearing change might be offset by your tire size increase. Your larger tires should be causing you to read slow now. The deeper gears will make you read fast. 4.10s might put you make to even. Maybe.

 

[Martinjmpr]

Yes- it’s for both axles.

And the gearing change might be offset by your tire size increase. Your larger tires should be causing you to read slow now. The deeper gears will make you read fast. 4.10s might put you make to even. Maybe.

Should be fairly close. I calculated my actual miles (as measured on a GPS) compared to what showed on the odometer after I put the new tires on and came up with a 1.7% error, so now when I figure MPG I take the odometer miles and multiply by 1.017 to get true miles driven.

By my calculation the difference between a 4.10 and a 3.73 gearset should be a 10% difference, but of course that's "on paper." I'd want to actually drive and measure with a GPS before I knew what the true "error" was. If my numbers are correct then what would be a 10% reduction would actually work out to more like an 8% difference once the larger tires were factored in.

 

[XJLI]

Get more gear, going to 4.10s wouldn't be worth the cost. Go to 4.56s.

 

[rayra]

Too tall. You aren't driving anywhere on the highway in a hurry with a 4spd and gear that tall. Ask @Stryder106 about that. Then again Martin's almost always towing on the long hauls, so it wouldn't be much of a detriment.
Need to get someone in here with a Sub with 4:10s. or more words about it from Todd. IIRC Stryder also made an intermediate change as he went with bigger then bigger tires.

Stryder's build topic, ought to be in the last couple pages
https://www.expeditionportal.com/forum/threads/my-02-avalanche-nfe.158253/

eta IIRC it's a programming tweak to re-calibrate. You're gonna pay for access to someone's $2000 tool.

 

[Ducky's Dad]

Forget about recalibrating the speedo and odo, unless you want to get a programmer/tuner like an Edge Insight. It's easy enough to calculate your actual vs indicated speed at a few data points and then do the conversion in your head while you are driving. If you know your speedo is reading 6% low, then you can figure you are no more than four over at indicated 70. Remember that the factory speedo ALWAYS reads high on a stock vehicle. Re the programmer idea, I'm a bit surprised no one has mentioned that possibility. It may not be ideal but is inexpensive and practical. Example: My 5.7 Power Wagon used to have some trouble pulling mountain grades on 35s with a heavy load (about 8500 pounds net, no trailer). I already had a CAI and cat-back exhaust, but adding the Edge made a huge performance difference on a moderate tune. I think the biggest improvement was in the reprogramming of the trans shift points, probably aided by a bit of extra power and torque. When I talk about pulling grades, I mean 75-80 uphill, passing the diesel bros pulling their toyhaulers. As an added advantage, the Edge allows you to recalibrate the speedo pretty easily if you feel the need to do that.

Forgot to mention that the Edge tune also pretty much eliminated the trans hunting for gears in the mountains.

Note: Just edited to fix my backassward explanation of stock speedos.

 

[BPD53]

Get more gear, going to 4.10s wouldn't be worth the cost. Go to 4.56s.

I agree. I wish I'd gone with 4.56s when I was building my heap.

Too tall. You aren't driving anywhere on the highway in a hurry with a 4spd and gear that tall.

Need to get someone in here with a Sub with 4:10s. or more words about it from Todd. .

I'm running 4.10s and wish I could get just about 200 more rpms while pulling the WV hills in overdrive. Like I said earlier, I feel like the 5.3 doesn't make enough power under 2200 rpms. Please take into consideration that WV is a far cry from the big mountains out west but WV still has some steep climbs.

I guess it all depends how fast a guy wants to drive/tow. I consider 65-70 mph to be pretty fast in my truck. The terrain being traveled is everything. There isn't enough flat ground in WV to stand on let alone build a road on. I swear its uphill in both directions. The deeper gears would really wake up a 5.3 where I travel.

The 5.3 doesn't mind sustained rpms in the neighborhood of 2250ish. A 4l60e in overdrive with 33" tires and 4.56s would run around that at 70mph on the interstate. Dropping down into 3rd around 65-70 mph would put you roughly 3000 rpm which is still acceptable for a pull.

I know next time I'm going with 4.56s. Don't get me wrong, the 5.3 is not a turd with 4.10s but things can always be better.

 

[Hillbilly Heaven]

One of the best online gear calculators. Has about every modern transmission ratio. Very flexible and user friendly. Allows comparison between 2 setups.

Gear Ratio Calculator

 

[rayra]

Most i have around here are a couple 4100' passes, one near the house I have to hit heading north and west and the other on the far end of L.A. (Conejo Grade, I-15), both are long slogs when heading north. I just vroomed up Conejo ~48hrs ago taking a longcut around the terrible sunday eve traffic westbound on the 210, 10 and 60 fwys. It's 30mi further the long way around the bulk of L.A. but over an hour faster with much less traffic, looping around the high desert.
My Sub's running about 6200-lbs with a couple people and and some stuff in it. If I can have free running I can keep it in the powerband over 75mph up those grades. But any moderate traffic and fast lane campers and I bog down a bit and then I'm falling down into 3rd and pushing hard to get back in the higher band when I can.

martin's got the factory 'tow package' and I'm trying to remember if the vehicle manual says to leave it in overdrive or put it in 3rd when tow mode is engaged. I also haven't asked martin if he uses that mode, I'm sure he does. But I also recall that it doesn't stay engaged after a vehicle shutoff, you have to turn it back on. I've forgotten that a few times. And it's mostly about a computer change of shift points. I'm not sure how it helps or hurts when stuck in a long laborious climb of a 11,000' peak that he makes.

The GMT800 k1500 tow package vehicles with factory Class III winch have a 12000-lb GVWR. A Sub fully loaded with family and gear and a trailer likewise, his rig is at least 10,500-lbs. Maybe 11k fully wet, both Sub and trailer. Even trying to go light on fluids until near the destination or over that killer grade would only save maybe 300-lbs, max. Barely 3% of the load. Seems like re-gearing or improving engine performance are about the only things that could help.

 

[Martinjmpr]

Most i have around here are a couple 4100' passes, one near the house I have to hit heading north and west and the other on the far end of L.A. (Conejo Grade, I-15), both are long slogs when heading north. I just vroomed up Conejo ~48hrs ago taking a longcut around the terrible sunday eve traffic westbound on the 210, 10 and 60 fwys. It's 30mi further the long way around the bulk of L.A. but over an hour faster with much less traffic, looping around the high desert.
My Sub's running about 6200-lbs with a couple people and and some stuff in it. If I can have free running I can keep it in the powerband over 75mph up those grades. But any moderate traffic and fast lane campers and I bog down a bit and then I'm falling down into 3rd and pushing hard to get back in the higher band when I can.

martin's got the factory 'tow package' and I'm trying to remember if the vehicle manual says to leave it in overdrive or put it in 3rd when tow mode is engaged. I also haven't asked martin if he uses that mode, I'm sure he does. But I also recall that it doesn't stay engaged after a vehicle shutoff, you have to turn it back on. I've forgotten that a few times. And it's mostly about a computer change of shift points. I'm not sure how it helps or hurts when stuck in a long laborious climb of a 11,000' peak that he makes.

I do use the tow/haul mode religiously when the trailer is hooked up.

As for having it in 3 or D while driving, any more I just leave it in D. It doesn't seem to make any difference. If the trailer is hooked up and the truck is in tow/haul mode, even the slightest upgrade will cause it to drop out of 4th anyway (I can tell by watching the RPMs.) So I don't think it matters if I have it in D or 3 since any kind of uphill will drop it into 3rd.

At ~65mph (my average flat-road cruising speed) engine speed is about 2000 RPM in OD (4th.) Dropping down to 3rd will cause it to jump to about 2900 - 3100 or so. When ascending a steep grade it will usually stay in 3rd until I bog down to about 40 mph at which point it will drop to 2nd and RPMs jump significantly to about 4100 - 4300. This is why I've said the 4L60 really needs a gear between 2nd and 3rd because while 3rd is clearly too high, 2nd is way too low and causes my speed to drop, which loses momentum, which requires more effort to move forward, etc. Sometimes if my speed has dropped significantly and I'm climbing the grade it will drop momentarily from 2nd down to 1st and RPMs are almost 5000 (I think redline is 5500 on this engine?) It typically only stays in 1st for a few seconds and then drops back to 2nd but it's a jarring experience and can't be good on the engine, the transmission or any other components.

Those who live on the Colorado Front Range know what roads I'm talking about: I-70 going West from Golden to Genesee the elevation goes from 6000' to 8000' in about 5 miles. From Georgetown to the Eisenhower Tunnel it goes from roughly 7500' to 11,000' in about 12 miles. Berthoud Pass is pretty much the same except it's higher (11,500') and the road is a twisty 3-lane (2 lanes uphill and 1 lane downhill) so speeds are low anyway.

All in all, it just annoys me that I can no longer get a full sized truck with a manual transmission. I never had these kinds of issues when I was shifting my own gears (full disclosure: I never pulled a trailer up these passes either. )

 

[Todd780]

Need to get someone in here with a Sub with 4:10s. or more words about it from Todd. .

Who me? Uh oh. What did I do now?

 

[rayra]

was just saying you had 4:10, maybe tell us more about your experiences with it. pluses and minuses sort of thing.

what Martin's just posted about how badly he's bogging down makes me think he needs a lot more hp / torque or should maybe skip the 4:10 altogether and go for the even taller gear. I'm inclined to point at the bouts of 5000rpms as at least as responsible for the trans failures than any prior heat issues. That the repeated cycles of slamming in and out of gear ranges and holding the high RPMs are causign as much trouble for the trans via fluid pressures than heat stresses (but pressure and heat go together, too).

Martin, if you were to stop on this murderous grade, what speed or gear could you reasonably maintain say under 3000rpm? Could you even get it to stay in 2nd in that rpm / power range? Your vehicle config and the grades you are taking might just be a lethal combo. And if you are keeping your foot in it trying to maintain a higher speed, or trying to strain back up into a higher gear just to lose it again and the trans keeps getting slammed in and out of shifts under that load, being held at very high engine RPMs, that combination may be what's killing it, and could very well kill your new trans too.

Might need to consider some engine mods to boost your hp/torque, And the least complex and common advice is cold air intake, easier breathing filter, and headers. Beyond that it gets expensive, with switchable tuning systems and changing internal engine components. I'm curious enough to look into the bolt-on stuff for my own purposes...

 

[Todd780]

was just saying you had 4:10, maybe tell us more about your experiences with it. pluses and minuses sort of thing.

Oh man. I owned that 2000 Sub 16 years or so ago... My memory ain't that good, lol

That truck was 100% stock. Pretty sure I got about the same fuel mileage I did with my 2009 Suburban with a 5.3L, 6 speed and 3:73's. No clue why, but I don't recall any significant difference.

The 4:10's were fine for me. But, I never towed with that truck and as I said, it was stock. So not turning big heavy rubber or anything. I didn't go looking for a Suburban with 4:10's. that one just happened to have them.

 

[rayra]

~$300 for a cold air intake setup, lots of anecdotal performance improvement, 12hp / 12ft-lbs of torque, which doesn't seem like a lot, but the motor is only rated around 270/315. So that's 4-5% gain and who's to say if that's enough to keep Martin's in a better power band / gear

~$300 for swap-in 'shorty' headers and while the whole idea of headers is to reduce backpressure and improve cylinder scavenging so MOAR fuel-air mix can be drawn in, if you don't open up the rest of the exhaust system you might not gain much. And there's two catalytic converters on these pigs, one on each side.

I'll have to go dig around for dyno reports. There's no end of them for vortec motors in camaros and corvettes, but never really looked for them in a Sub's LM7 motor.