SoCalDesertRider wrote: Yes, this is why I will only ever own 4wd trucks that have manual locking hubs and manual shift transfer case. I use my transfer case in 4-Low with the hubs unlocked very regularly. I get the full power of 4-Low, without any driveline bind on hard surfaces, since the hubs are un-locked. Hooray for manual locking hubs! I hate those stupid vacuum auto hubs...
Be careful. Using low range in two wheel drive can break driveline parts very easily due to torque multiplication.
True, however, not any more easily than when running 4-Low with the hubs locked. The rear driveshaft and axle still receive the same torque multiplication stress whether the front axle and driveline are engaged to the transfer case or not. The transfer case doesn't halve the torque output when in 4wd, it sends out the same amount of torque either way (2wd or 4wd), just sends it out in both directions when the front driveline is engaged.
True but,,,,,and it's a big but.
When the front axle is engaged some of the force will drive the wheels so not all of it will go to the rears. Using 2wd only, 100% of the power ALWAYS goes to the rear. If you have a locking rear diff, and one wheel loses traction, then 100% of the power will go to the one wheel that has traction. This is how axles break.
Do some research on 4wd and figure out just how much your particular gear ratios multiply torque.... The final figure will be staggering. It WILL be more than a single axle shaft can sustain, and sometimes more than both.
It's hard on other things too I have a old Blazer and the owners manual warns of this,,,they state that the carier bearings will be overloaded. It can snap U joints as well
Huntindog
2010 Palomino Sabre 30BHDS TWO bathrooms...No waiting!
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2011 Silverado Big Dually 3500 4x4 CC D/A
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True about the 4lo in rwd only. BUT, some of us are running larger R&P's in our 35 series trucks, so they SHOULD/MIGHT be able to handle this torque multiplication vs the older blazer. Assuming a K5 blazer frankly! BUT, being as not too many rigs have manual hubs these days, or the ability to shift into a 2lo if you will, this is not always the best way to plan on getting up a hill if one runs out of LOW gears! Then again, a lot of us are probably NOT having to gun the motor if you will when this option is needed, so we should be able to run 2lo if you will with out too many issues.
marty
05 Chev CC D/A LS Dooley
92 Navistar dump truck, 7.3L 7 sp, 4.33 gears with a Detroit no spin
00 Chev C2500, V5700, 4L80E, 4.10, base truck, no options!
92 Red-e-haul 12K equipment trailer
3 Single axle utility trailers
I'm coming up with mid 12K lb ft of torque. BUT, IIRC my TC is about 1.8. It could be a bit more in the 2.x range. BUT as I recall the duallys have a lower/taller ratio than the SW rigs which are in the 2.x range. I have 620 torque, 3.09 first with a TorqueConvertor of ~1.8. which was not used before, so reality is, with the TC I could be in the 22K TQ! so more yet to work with! long with more to blow things up.
Worth looking up specs to the C14.5 with 11.5RG that I have. SWAG'ing SC's rigs have a 10.5 RG, so a bit less strength to work with. I'm pumping out 15K tq with my navistar with its 10.08 granny, 433 gears and 335 lbft of torque into a 15.5K spicer. Not sure HOW big that gear set is. Altho I had an employee that liked to pop a clutch, blew up a Detroit locker in it! Got rid of employees, no issues with that any more! More torque yet gets pumped into that axel with some of the newer motors!
I do nto think either SC or I is saying one can not blow up an axle in 2lo per say. Yes a blip of the throttle with do that!
Do you remember the old granny gear 4 speed transmissions? The ones with between 6:1 to 7:1 first gear ratios (Borg Warner T18 & T19, Muncie SM465, New Process NP435, etc)? Running a normal 3:1 first gear ratio with a 2:1 transfer case ratio in 2wd is the same as running a 6:1 first gear ratio in a granny tranny in 2wd, torque multiplication is the same, just done in 2 different gear boxes versus one.
Yes, stuff can break, but I don't see running the t-case in 4-low with the hubs unlocked being any more dangerous to the drive train than using a granny tranny in low first gear in a 2wd truck. Granny trannys were used successfully and reliably in trucks for a few decades before they went out of style in the 80's. I've been using the 2wd-low position in the Dana 20 t-case in my Bronco for years and haven't broken anything that can be attributed to having too much torque multiplication going to the rear axle. Can it happen? Sure, anything can happen. I don't use it abusively so I don't worry about it being a problem.
Yeah had one of them in my 81 GMC, twin sons still drive it. Not that that rig would torque the gears with a 292I6 and 4.10's. I had an 88 K3500 with IFS, think the last 30K miles or so might have had the FA thingy broken. So was using 4lo a lot with a TBI454. Then again, a TH400 does not have a LOW first gear. If anything TOO tall a first gear!
I do think some of the D70/C14 -10.5 or 11.5" RG and equal setups from Ford or Dodge would also handle the torque of a 2Lo if you will as long as one does not abuse the power one has. Ie idle it or keep the rpms in the less than 2000 range for some of the diesels and maybe 2500-3000 for the gas rigs. Along with NOT punching it! so yes a 2lo/4looption on my rigs would be nice!
It will work until the one time you exceed the limit. You can go right to the limit 100s of times, but exceed it once by 1 pound and it WILL break.
Your axles have ratings for this. Find out what they are, then do the math for your gears and motors torque. Then you will KNOW just how close you are to breaking axles.
And if you don't have enough power to climb the hill in Hi range then you obviously will need more torque to get the job done. So you will need to use a lot of the motor.
Yes your trucks have beefier axles than my old K5. But they also put out a LOT more torque, and have lower range transfer cases and 1st gears.
The Blazer has a 2:1 transfer case and a 2.56 first gear and 3.73 rearend.
IIRCC, the Blazer came with around 255 TQ.
So 255 x 2.56 (1st gear)x 2 (lo range)x 3.73 (rearend)= 4870 TQ.
I'm gonna guess at what your trucks have, but it should be pretty close.
Motor TQ 530 x 3.06 (1st gear) x 2.6 (lo range) x 3.73 (rearend) =15,728 TQ !
So possibly 15,728# of torque could be applied to a single axle.
An accidental blip of the throttle at the wrong time and it WILL break.
I agree about having all the facts. I've done plenty of torque/rpm/gearing calculations on my truck over the years and played with all the numbers in every way imaginable and done plenty of hypothetical scenarios involving other engines, transmission, t-case and axle ratios, etc as well. Follow any of my posts here on the forum on axle ratio topics and you'll see that I can get very detailed and mathematical when I need to. Marty, Ben and the other regulars here can all attest to that.
Yes, getting it going and acceleration is 'part' of the ratings, specifications,
performance, etc.
But too many either neglect or don't understand that maneuvering and deceleration
(braking) are also part of the ratings, specifications, performance, etc.
The easier/faster you can get it going, especially 'heavy' load...the more it
has to have maneuvering and braking performance to match
-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...
Huntindog wrote: It will work until the one time you exceed the limit. You can go right to the limit 100s of times, but exceed it once by 1 pound and it WILL break.
Your axles have ratings for this. Find out what they are, then do the math for your gears and motors torque. Then you will KNOW just how close you are to breaking axles.
And if you don't have enough power to climb the hill in Hi range then you obviously will need more torque to get the job done. So you will need to use a lot of the motor.
Yes your trucks have beefier axles than my old K5. But they also put out a LOT more torque, and have lower range transfer cases and 1st gears.
The Blazer has a 2:1 transfer case and a 2.56 first gear and 3.73 rearend.
IIRCC, the Blazer came with around 255 TQ.
So 255 x 2.56 (1st gear)x 2 (lo range)x 3.73 (rearend)= 4870 TQ.
I'm gonna guess at what your trucks have, but it should be pretty close.
Motor TQ 530 x 3.06 (1st gear) x 2.6 (lo range) x 3.73 (rearend) =15,728 TQ !
So possibly 15,728# of torque could be applied to a single axle.
An accidental blip of the throttle at the wrong time and it WILL break.
Huntingdog,
You make a good point for sure, but this is a case where you just have to make some sort of a compromise. For instance, running 4Lo with hubs locked on dry pavement will do even more damage. And leaving it in 2wd may overstress the torque converter on some 4 speed autos with a not so low first / reverse (like 48RE).
Also, keep in mind just about any semi tractor has enough power to snap its axles in Lo gear, atleast over time. Some 18 speeds have 18:1 Lo gears, multiply the 2050 lb-ft torque of an ISX, by 18, and then by 4.11, and we get a lovely 151,660 lb-ft. Those merritor axles are strong, but not 9.6 times stronger than a Dana 110.
Seen drivers get diesel on their boots at a truck stop, with loaded B-trains, foot slips off clutch pedal by mistake, and well, there goes the axle.
Again, as a driver, these are the risks you have to take, because otherwise you'll be too hard on equipment (ironically) by running too tall of a gearing.
Yes, I agree. I never said not to do it. I said to be careful.
Most everyone is aware that running 2wd in low range increases the strain on the rearend. Most however are shocked when they actually do the math and see by how much.
Knowledge is power. It is better to know the facts than not.
Huntindog wrote: It will work until the one time you exceed the limit. You can go right to the limit 100s of times, but exceed it once by 1 pound and it WILL break.
Your axles have ratings for this. Find out what they are, then do the math for your gears and motors torque. Then you will KNOW just how close you are to breaking axles.
And if you don't have enough power to climb the hill in Hi range then you obviously will need more torque to get the job done. So you will need to use a lot of the motor.
Yes your trucks have beefier axles than my old K5. But they also put out a LOT more torque, and have lower range transfer cases and 1st gears.
The Blazer has a 2:1 transfer case and a 2.56 first gear and 3.73 rearend.
IIRCC, the Blazer came with around 255 TQ.
So 255 x 2.56 (1st gear)x 2 (lo range)x 3.73 (rearend)= 4870 TQ.
I'm gonna guess at what your trucks have, but it should be pretty close.
Motor TQ 530 x 3.06 (1st gear) x 2.6 (lo range) x 3.73 (rearend) =15,728 TQ !
So possibly 15,728# of torque could be applied to a single axle.
An accidental blip of the throttle at the wrong time and it WILL break.
Huntingdog,
You make a good point for sure, but this is a case where you just have to make some sort of a compromise. For instance, running 4Lo with hubs locked on dry pavement will do even more damage. And leaving it in 2wd may overstress the torque converter on some 4 speed autos with a not so low first / reverse (like 48RE).
Also, keep in mind just about any semi tractor has enough power to snap its axles in Lo gear, atleast over time. Some 18 speeds have 18:1 Lo gears, multiply the 2050 lb-ft torque of an ISX, by 18, and then by 4.11, and we get a lovely 151,660 lb-ft. Those merritor axles are strong, but not 9.6 times stronger than a Dana 110.
Seen drivers get diesel on their boots at a truck stop, with loaded B-trains, foot slips off clutch pedal by mistake, and well, there goes the axle.
Again, as a driver, these are the risks you have to take, because otherwise you'll be too hard on equipment (ironically) by running too tall of a gearing.
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