GM genuine OE high/low planetary carrier for the NP246 transfer case on 1998-2007 GM 1500/2500 trucks and SUVs with chain-drive 4x4.
If your 1998-2007 Silverado, Sierra, Tahoe, Yukon, Suburban, Avalanche or Escalade grinds or whines only after you push the 4LO button, or jumps out of low range when you pull hard, the low-range planetary carrier in the NP246 (RPO NP8) transfer case is the first suspect. This is the genuine GM carrier assembly, part number 84635180, which GM lists as replacing 12547997, 19299091, 88958816 and 89059196.
The NP246 is GM's electronic-shift AutoTrac case: a chain drives the front output, an electronically controlled clutch pack handles Auto 4WD, and a planetary gearset at the front of the case supplies low range. In 2HI, AUTO and 4HI the range hub locks the input straight through and the planetary turns as one unit with almost no load. Select 4LO and the encoder motor slides the range hub onto the carrier, so the input sun gear drives the pinions around the ring gear and the carrier turns the mainshaft at roughly a 2-to-1 reduction. That means the carrier only works hard in low range, which is why a worn one can stay quiet for years and then complain the first time you need it.
Run the truck in each range. Noise that follows the front output in AUTO, 4HI and 4LO points at the chain, not the carrier; a leak or howl from the rear case half points at pump rub. Our NP246 planetary carrier failure guide walks through separating those, and the 4L60E whine vs clunk diagnosis helps rule out the transmission behind it. Scan the transfer case module for codes too: Transmission Digest notes the NP246 logs C, B and U codes, and an encoder or motor fault can mimic a range problem. Once the case is split, pinion end play, pitted teeth, blued pinion shafts or worn hub engagement teeth confirm the carrier.
This carrier is listed for the NP246 behind the 4L60E and 4L80E in 1998-2007 GM 1500 and 2500 trucks and SUVs with the push-button automatic 4WD case. GM's own catalog shows 84635180 across a much wider span of 4x4 trucks, because GM uses this carrier in more than one transfer case, so the case tag matters more than the truck badge. Check the tag on the case for NP246 / NP8, and if you are unsure, send us your year and VIN before ordering. Browse the rest of the drivetrain for these trucks on our 4L60E parts page and 4L80E parts page.
Because this is the GM part rather than a reproduction, it uses the stock sun gear, range hub and shafts with no machining.
| Part Number | 84635180 (also 12547997, 19299091) |
| Fits Transfer Case | NP246 (NP8) |
| Vehicle Fitment | 1998-2007 GM 1500/2500 trucks & SUVs: Silverado, Sierra, Suburban, Tahoe, Yukon, Avalanche, Blazer (chain-drive auto 4x4) |
| Weight | 7.14 lb |
| Brand | GM Genuine Parts |
| Warranty | 30-day replacement |
| Ships | From the USA |
If the case tag reads NP246 (RPO NP8), yes - that push-button AutoTrac case is what this carrier is listed for on 1998-2007 GM 1500 and 2500 trucks. Manual-lever and other push-button cases use different internals, so read the tag or send us your VIN.
Noise in 4LO only points at the planetary carrier, because it carries load only in low range. A stretched chain makes noise in AUTO, 4HI and 4LO, since it drives the front output in every 4WD mode.
The input bearing and seals (a BK-351 style kit), the oil pump or a pump rub upgrade if the rear half shows wear, and the chain if it measures stretched. All of them wear together and the case is already apart.
Use the GM-specified transfer case fluid listed in your owner's manual for your year. Do not use gear oil; it changes how the Auto 4WD clutch pack and bearings behave.
Yes. GM's parts catalog lists 84635180 as the current number replacing 12547997, 19299091, 88958816 and 89059196, so any of those old numbers on your paperwork leads to this carrier.
No programming is needed for the carrier itself. If the encoder motor was unplugged or replaced, cycle through every range with the truck stopped and confirm the dash lights match before driving.
