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No Torque/Loud Engine 2006 Jeep GC

I have an issue with my 2006 Jeep Grand Cherokee v8 Laredo that has been bothering me for a little over a year now. When the temperature gets warm out (over 80) and I am traveling on the interstate up a long hill (65-70 mph, towards the end of my commute so about 30 miles in or about 30 minutes) my engine randomly begins to sound like I am in the wrong gear (RPMs do not change but engine sounds like I just changed to second) and I loose quite a bit of torque. I can maintain my speed but my engine sound horrible. After about 10 minutes of this my engine goes back to normal and I can accelerate without issue. Then randomly it goes back to being loud with low torque. To add to the the fun, if this happens at any time during the day, the next day when I start my Jeep the issue resurfaces and I have no torque for about 10 minutes (5 miles) then all is well for the rest of my commute (40 miles downhill). I had a diagnostic scan done and they found nothing wrong and I also just got both of my exhaust manifolds replaces but the issue continues. Any suggestions?

Since a scan showed nothing I would have the catalytic converter checked. It may be plugging up on you.

I am bringing it in to another mechanic tomorrow and I will ask about it. Seems like it wouldn’t be an issue of outside temperature with the catalytic converter though, as I would think it would plug up based on the engine and exhaust temp. Since my engine sounds off in the morning after it happened and when everything is cool makes things that much more odd.

I am going to guess it’s your fan clutch. I belive this truck still has a belt driven fan. This fan has a clutch that engages and disengages the fan. If it fails it can feel like it’s sucking power and will get very loud. Sounds like it could be your culprit.