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Automotive HD/Fleet Forum

Professional automotive forum for discussion of heavy-duty trucks, buses and other on- and off-road equipment, and maintenance of automotive fleet vehicles. Discussion topics include fuels and lubricants, hydraulics, performance, on-board diagnostics, powertrain, power distribution, anti-lock braking and stability control systems, and best practices as they relate to heavy duty and fleet maintenance. This forum is for experienced automotive repair professionals only, membership required.

Continue to the description of our next automotive discussion forum, the HVAC Forum.

Recent Automotive Discussions in the Automotive HD/Fleet Forum

6.7 Powerstroke Cooling system service
07/02/2026 in the HD/Fleet Forum
[Engine: 17 Ford F-250 Super Duty King Ranch 6.7L] Need to do a service on the cooling systems. It has a primary and secondary system. I am not sure how to handle this job. I see where there is some sort of additive that can be added as well as the coola...
Ford 6.7 Engine Replacement
07/01/2026 in the HD/Fleet Forum
[Engine: 14 Ford F-250 Super Duty Lariat 6.7L] Got a long shot. Pulled my first cab to replace an engine. Got engine in and cab back down. Trying to get it finished before i leave on vacation. Engine starts but had an extended crank. Runs good, has oil p...
E-One power steering
06/23/2026 in the HD/Fleet Forum
[Chassis: 17 Emergency One Emergency One 8.3L] Hi HD, We have been working on this E-One fire truck for months. The local county facility replaced both steering boxes. It has a Reyco front suspension with TAS 85 boxes. Both boxes were brand new (and the ...
A/C Clutch Power
06/23/2026 in the HD/Fleet Forum
[HVAC: 16 International 4300 6.7L] I am working on a 2016 International 4300 with a Cummins 6.7L. Brought in for A/C work. Everything is functioning besides the compressor clutch, system is charged properly. When I look at it with DLB, I can see pressure...
KW T370, Code present, derate warning on dash, no MIL
06/17/2026 in the HD/Fleet Forum
2022 Kenworth T370, PX9/L9 VIN [...] This truck initially came in for MIL, Derate 3725, aftertreatment 1 intake NOX sensor abnormal rate of change. 15685, brake switch, abnormal update rate, a couple of codes for running the DEF level too low, and some co...

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