Transmission and drivelineModel years 1998–2007Repair business
Transfer case pump rub (hole worn through rear case half)
1998-2007 GM transfer cases NP136, NP149, NP236, NP246, NP261, NP263 and HD/XHD variants
FaultCrate・Transfer case pump rub (hole worn through rear case half)
The hole appears in the upper part of the housing and does not leak when parked, leaving little or no evidence on the driveway.
The magnesium case is softer than the aluminum pump, and pump movement in normal operation eventually wears a hole in the rear case half.
The factory spring steel anti-rattle clip does not protect the case in the long term.
What to do
- Fluid loss is hard to notice without going under the truck and removing the fill plug to check the level.
- Larger locating tabs prevent the pump from rubbing through the case as it moves.
If left
- The transfer case holds only two quarts, so fluid loss can quickly become catastrophic for the internal components.→ transfer case internal components
- Pump rub is very often fatal to transfer cases because the vehicle is often driven thousands of miles before problems show.
Applies to
- The 1998-2007 GM transfer cases (NP136, NP149, NP236, NP246, NP261, NP263 and HD/XHD variants) use an internal pump for lubrication.
See the evidence (1 documents, 8 passages)
| Document | Publisher | Date |
|---|---|---|
| [1]Permanently FIX Your 1998-2007 GM Transfer Case ↗ | Repair businessMerchant Automotive (vendor of the upgrade kit) | 2021-05-25 |
Applies toThe 1998-2007 GM transfer cases (NP136, NP149, NP236, NP246, NP261, NP263 and HD/XHD variants) use an internal pump for lubrication.
The design of the 1998-2007 GM transfer cases (NP136, NP149, NP236, NP246, NP261, NP263, NP261HD, NP263HD, NP261XHD, and NP263XHD used in Cadillac, Chevrolet or GMC pickups, SUVs, and vans) uses an internal pump to lubricate the internal components— [1]
Why it happensThe magnesium case is softer than the aluminum pump, and pump movement in normal operation eventually wears a hole in the rear case half.
While both metals are soft, the magnesium is considerably softer than the aluminum and pump movement during normal operation will eventually wear a hole in the rear case half.— [1]
Why it happensThe factory spring steel anti-rattle clip does not protect the case in the long term.
A small spring steel anti-rattle clip is installed from the factory to mitigate the movement and wear, but the anti-rattle clip is not up to the task for long term case protection.— [1]
First signsThe hole appears in the upper part of the housing and does not leak when parked, leaving little or no evidence on the driveway.
the hole appears in the upper portion of the transfer case housing and does not leak when parked leaving little to no evidence in the driveway.— [1]
How to confirmFluid loss is hard to notice without going under the truck and removing the fill plug to check the level.
unless you actually climb under your truck and pull out the fill plug to check the transfer case fluid level it is not easy to know when there is a loss of fluid.— [1]
If leftThe transfer case holds only two quarts, so fluid loss can quickly become catastrophic for the internal components.
the transfer case only holds two quarts of fluid so any loss of fluid and lubrication can quickly become catastrophic for the internal components.— [1]
If leftPump rub is very often fatal to transfer cases because the vehicle is often driven thousands of miles before problems show.
Pump rub is very often fatal to transfer cases because in many cases the vehicle is driven for thousands of miles before transfer case problems rear their ugly head.— [1]
RepairLarger locating tabs prevent the pump from rubbing through the case as it moves.
the larger locating tabs prevent the pump from rubbing through the case as it moves during operation.— [1]
Put together by FaultCrate from public records and technical documents. The cause and the repair are for the workshop to decide with the vehicle in front of it. Counts are records, not failure rates.
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