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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

FICM connector issues
06/24/2025 in the HD/Fleet Forum
[Driveability: 05 Ford Excursion Eddie Bauer 6.0L] Needed to replace the ficm, and the lock tabs were broke. Did what I could, but now,Thanks!it dies and won't crank at times-get the 105 code. It does run and start at times, but I think that the front co...
ISUZU NPR with Diesel
06/23/2025 in the HD/Fleet Forum
I have a customer looking at some used 2018 NPR Chassis. They have the 4HK1TC engine with Allison 2550 RDS engines. Miles are 95,000 to 115,000. I see these around but don't know a thing about them. My main question is, what is the normal lifespan for the...
QLS Blues
05/30/2025 in the HD/Fleet Forum
Hi Everyone, Happy Friday! I have a 2017 Freightliner M2 Grade all for a local city here. It has a failed QLS and are on backorder for 2-3 months. P#04-35960-000. NO ONE in the country has one. Does anyone know what exactly goes wrong with them? Can somet...
Long crank hard start
05/30/2025 in the HD/Fleet Forum
[Driveability: 13 Mack GU8 GU800 12.8L] I have a Mack with a long crank/hard start issue... There are times I think the starter is going to burn up before starting and the next day, it fires up line a new truck. I have had it sitting for a week and it fi...
High press fuel system
05/22/2025 in the HD/Fleet Forum
[Driveability: 19 Ford F-550 Super Duty 6.7L] Group, This truck had a fuel system replaced 7 months ago, cust complains of power loss, however cleared all codes before bringing it. I can't duplicate his problem, we are on pretty flat ground here so it's ...

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