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Old 02-24-2016, 08:43 PM
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2013 Manual Rubicon; 2WD Engagement Drops Out

2013 Rubicon
Manual Transmission
50,000 miles

Driving in 2WD in cruise control at speeds ranging from 30-70 mph (straight) on dry roads
The car suddenly makes two thuds, then immediately drops about 750-1250 rpms. No sharp noises, almost like it falling out of the transfers albeit fully engaged in whatever respective gear I was in.

At first I thought it was the cruise control dropping out over an ABS, or some safety feature.

Now when driving straight in 2WD the car at a constant throttle will make the same two thuds, drop in rpm, and then return after 3-5 seconds to normal throttle control; ie return back to the same RPM per displacement of accelerator.

I am not sure if this vehicle has mechanical engagement on the gear shift and/or the 2WD, 4WD-HI, 4WD-LO or if it is an electronic shift.

I am not sure where the issue is originating from.

I did just replace just one axel's worth of wheels but in 2WD I figured it would not matter at the different circumference amounts.

Anyone have two bits on this one?

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Old 02-24-2016, 09:00 PM   #2
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What size tires are you running?
Tire size matters, a worn front and a new rear isnt a big deal, but if you have 33's in the front and 35's in the rear, you will have a problem.

Any codes?

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Old 02-24-2016, 09:02 PM
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Quote:
Originally Posted by Tweak View Post
What size tires are you running?
Tire size matters, a worn front and a new rear isnt a big deal, but if you have 33's in the front and 35's in the rear, you will have a problem.

Any codes?

The stock tires on front (rotated twice and are originals), and the replacement stocks on the rear. essentially near enough the same.

No error codes
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Old 02-25-2016, 06:46 PM   #4
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does it feel like the rear end jumps? mine does the same thing 2-6th gear. Happens more often going up a slight incline. example 6th gear cruise control 70mph right around 2k rpms just hit an incline and the jeep "jumps" and rpms drop and comes out of cruise control. also happens non cruise control 2nd to 3rd gear. its weird when I get time im going to the dealer seeing as I bought it one month ago. 13JKU 6 speed.
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Old 02-25-2016, 07:21 PM   #5
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Everything is mechanical. If you are travelling the same speed there is nothing that can allow RPM to drop in a manual transmission unless it actually comes out of gear, the clutch is depressed, or it breaks something.
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Old 02-25-2016, 08:24 PM   #6
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Is the engine hesitating? Possibly cutting out then continuing? Loose/dirty/worn grounds will do that.
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Old 02-28-2016, 11:27 AM
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Originally Posted by Batman804 View Post
does it feel like the rear end jumps? mine does the same thing 2-6th gear. Happens more often going up a slight incline. example 6th gear cruise control 70mph right around 2k rpms just hit an incline and the jeep "jumps" and rpms drop and comes out of cruise control. also happens non cruise control 2nd to 3rd gear. its weird when I get time im going to the dealer seeing as I bought it one month ago. 13JKU 6 speed.
The experience is very similar if I were to drop out off of cruise without a food on the brake. however twice the drop in deceleration.
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Old 02-28-2016, 11:30 AM
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Originally Posted by Potatohead View Post
Everything is mechanical. If you are travelling the same speed there is nothing that can allow RPM to drop in a manual transmission unless it actually comes out of gear, the clutch is depressed, or it breaks something.
my initial estimation of rpm drop was incorrect. when monitoring it closely now, the rpm drop is 100-200 rpm.

Before and after the event, the transmission is fully engaged with clutch not touched.

I purchased an ODB2 to see if I can use this to gather additional information.

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