C12 Jake brake cuts out in 7th gear

Old 05-05-2023, 07:47 PM
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Join Date: May 2023
Location: Montana
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Exclamation C12 Jake brake cuts out in 7th gear

Just bought a new to me truck. 99 peterbilt 379. C12 Cat. Eaton 10 spd. The Jake brakes cut out while down shifting but only in 7th gear and only between 1200 and 1000 rpm’s.
Happens every time. It will Jake brake the whole range of rpm’s in every other gear but 7th. Local shop is baffled.
Old 08-30-2023, 09:50 AM

It sounds like you're dealing with a perplexing issue on your new Peterbilt 379 with the C12 Cat engine. The Jake brake problem in 7th gear between 1200 and 1000 rpm's must be quite puzzling. Have you considered checking the components with a resource like partstree? Sometimes, a specific part can be the culprit behind such quirks, and having a thorough look might help you pinpoint the issue. Best of luck getting this sorted out and enjoying your truck to the fullest!

Last edited by kira5; 09-04-2023 at 02:00 PM.

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