Locking hub - Chevy and GMC Duramax Diesel Forum
11-16 LML Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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post #1 of 12 (permalink) Old 01-10-2020, 12:43 PM Thread Starter
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Locking hub

Question on my 2011 Duramax 2500 do the hubs lock when you put it in 4 x 4 low? It feels like they are locked but are they truly locked?
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post #2 of 12 (permalink) Old 01-10-2020, 12:50 PM
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Originally Posted by Jessapio View Post
Question on my 2011 Duramax 2500 do the hubs lock when you put it in 4 x 4 low? It feels like they are locked but are they truly locked?
UPDATE: I don't quite know what the hell I'm talking about; see posts further down.

I'm fairly certain that the hubs on these trucks are statically locked, all the time. I.e., the front driveline is always turning; by putting it in 4WD you're simply locking the front driveshaft to the transfer case input shaft (or, equivalently, the rear driveshaft).

If your hubs weren't locking when you put the transfer case in 4WD, you wouldn't actually be in 4WD because your wheels wouldn't be connected to the driveline. Note that on a truck with auto-locking hubs that aren't working/engaging/seating fully, you'll hear grinding from the front end when you make turns on pavement. That's the sound of the splines on the hubs scraping against the splines on the axleshafts.

Bottom line: put the truck in 4WD and make a tight (and slow!) turn on pavement. If you feel it hopping, it's in 4WD and everything is probably working just fine.

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Last edited by jdwarren; 01-10-2020 at 04:38 PM.
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post #3 of 12 (permalink) Old 01-10-2020, 03:19 PM
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No locking hubs as the front wheels are connected to the axle via splines, the transfer case disengages the front driveshaft and the axles disengage via actuator within the front axle housing.

2001 2500HD 4WD EXTENDED CAB LS,
S&B CAI, 4" STAINLESS STEEL EXHAUST, EFI LIVE FROM ATP TRUCKS, EDGE CTS, PPE BOOST VALVE, BANKS INTERCOOLER PIPE, AIR DOG II 165, REBUILT TRANNY WITH SUNCOAST KIT, TRANSGO SHIFTKIT AND BILLIT TORQUE CONVERTER, NEW UPGRADED TAILSHAFT, PUMP RUB FIX ON TRANSFER WITH NEW ALUMINUM TAIL SHAFT, NEW TOW MIRRORS, NEW GAGE HEAVY DUTY FRONT AND REAR BUMPERS, BEANS SUMP, FUMOTO VALVE, RARE PARTS TIE RODS WITH COGNITO PISK, MAD JACK FUEL FILTER ACCESS DOOR, STAINLESS STEEL SPEED BLEEDERS.
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post #4 of 12 (permalink) Old 01-10-2020, 04:09 PM
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So the system has 2 actuators? I was under the impression it only has one in the tcase to engage the drive and another to shift the ranges. Wasn't aware of an actuator in the front diff.

2019 Chevrolet 4500HD CC 4X4 Flatbed
2018 Chevrolet 1500 CC 4X4 High Country 6.2 liter
2019 Chevrolet 3500HD CC 4X4 Flatbed--SOLD
2011 Peterbilt 337 hauler with 360HP 8.3 Cummins--SOLD
1957 GMC 1 ton flatbed with 22K original miles.
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2003 Chevrolet 2500HD CC: 2011 Chevrolet 3500HD CC 4X4 and 2013 3500HD ex. cab 4X4-- all sold.
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post #5 of 12 (permalink) Old 01-10-2020, 04:19 PM
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Yes they do.

2001 2500HD 4WD EXTENDED CAB LS,
S&B CAI, 4" STAINLESS STEEL EXHAUST, EFI LIVE FROM ATP TRUCKS, EDGE CTS, PPE BOOST VALVE, BANKS INTERCOOLER PIPE, AIR DOG II 165, REBUILT TRANNY WITH SUNCOAST KIT, TRANSGO SHIFTKIT AND BILLIT TORQUE CONVERTER, NEW UPGRADED TAILSHAFT, PUMP RUB FIX ON TRANSFER WITH NEW ALUMINUM TAIL SHAFT, NEW TOW MIRRORS, NEW GAGE HEAVY DUTY FRONT AND REAR BUMPERS, BEANS SUMP, FUMOTO VALVE, RARE PARTS TIE RODS WITH COGNITO PISK, MAD JACK FUEL FILTER ACCESS DOOR, STAINLESS STEEL SPEED BLEEDERS.
2011 GMC 3500HD DUALLY Welding Bed, 4WD CREW CAB, 4" downpipe back exhaust, def delete, egr delete, with new LB7 up pipe, pcv reroute, Fass 150, EFI live with DSP 5, HSP CAI. Air Lift Air bags. PPEI transmission tune.
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post #6 of 12 (permalink) Old 01-10-2020, 04:38 PM
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Quote:
Originally Posted by mray View Post
No locking hubs as the front wheels are connected to the axle via splines, the transfer case disengages the front driveshaft and the axles disengage via actuator within the front axle housing.
Quote:
Originally Posted by sambor View Post
So the system has 2 actuators? I was under the impression it only has one in the tcase to engage the drive and another to shift the ranges. Wasn't aware of an actuator in the front diff.
Seems he's right (see item 46 below, "shift fork assembly"). Although I can't quite figure out how all this actuation business works...




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post #7 of 12 (permalink) Old 01-10-2020, 04:58 PM
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I'll be damned. Its nice to know I can still learn at my age.
I'm like jw though-- hard to figure why they designed it that way. After reading the ops info it seems that front tires will not hop when turned sharp it seems. Thanks MRay for the info

2019 Chevrolet 4500HD CC 4X4 Flatbed
2018 Chevrolet 1500 CC 4X4 High Country 6.2 liter
2019 Chevrolet 3500HD CC 4X4 Flatbed--SOLD
2011 Peterbilt 337 hauler with 360HP 8.3 Cummins--SOLD
1957 GMC 1 ton flatbed with 22K original miles.
3 different Kubotas
2003 Chevrolet 2500HD CC: 2011 Chevrolet 3500HD CC 4X4 and 2013 3500HD ex. cab 4X4-- all sold.
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post #8 of 12 (permalink) Old 01-10-2020, 05:16 PM
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Quote:
Originally Posted by sambor View Post
I'll be damned. Its nice to know I can still learn at my age.
I'm like jw though-- hard to figure why they designed it that way. After reading the ops info it seems that front tires will not hop when turned sharp it seems. Thanks MRay for the info
They will hop/scrub on sharp turns on hard surfaces if in 4wd (high or low)
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post #9 of 12 (permalink) Old 01-10-2020, 05:38 PM
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Quote:
Originally Posted by sambor View Post
I'll be damned. Its nice to know I can still learn at my age.
I'm like jw though-- hard to figure why they designed it that way. After reading the ops info it seems that front tires will not hop when turned sharp it seems. Thanks MRay for the info
Quote:
Originally Posted by redwngr View Post
They will hop/scrub on sharp turns on hard surfaces if in 4wd (high or low)
@redwngr is correct; I know this is true in my truck. This is pretty much unavoidable in any system that includes a mechanical lockup between the front and rear driveshafts; the only way to eliminate it is to use a differential, viscous coupling, or other coupling between the driveshafts that allows for a difference in speed.

Actually, now that I think of it, there's a way to eliminate it while keeping the driveshafts locked together: four wheel steering.

2017 Silverado 3500 LTZ (Summit White) | CC SB SRW | Z71 | Duramax L5P | Undercover Ultra Flex bed cover | Draw-Tite front receiver | AIMS 3kw inverter-charger | Titan Travel Trekker 50-gallon auxiliary fuel tank | Reese under-bed FW/GN rail kit
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post #10 of 12 (permalink) Old 01-10-2020, 08:08 PM
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Mine hops too but if I am reading the last paragraph correctly they can rotate at different speeds according to the description of the diff which they call "open". I always compared mine to a go-cart style. Guess I am lost with this.

2019 Chevrolet 4500HD CC 4X4 Flatbed
2018 Chevrolet 1500 CC 4X4 High Country 6.2 liter
2019 Chevrolet 3500HD CC 4X4 Flatbed--SOLD
2011 Peterbilt 337 hauler with 360HP 8.3 Cummins--SOLD
1957 GMC 1 ton flatbed with 22K original miles.
3 different Kubotas
2003 Chevrolet 2500HD CC: 2011 Chevrolet 3500HD CC 4X4 and 2013 3500HD ex. cab 4X4-- all sold.
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