Newbie, Erratic downshifting from OD 2003 TJ - JeepForum.com
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post #1 of 6 Old 06-09-2018, 08:28 AM Thread Starter
Markpenn
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Newbie, Erratic downshifting from OD 2003 TJ

Newbie, 2003 TJ. While going along at I.E., 60/65mph and want to go a little faster or just slight grade, while applying slight throttle, the TJ will shift down somewhat erratically to fourth(?) and even seems like down to third(?). Just wondering, adjustments needed, torque converter going south, etc. It is very annoying. Any input is welcomed, thanks in advance.

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post #2 of 6 Old 06-09-2018, 09:02 AM
Duck Doctor
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The 42RLE has a deep OD of 0.69:1 causing the transmission to downshift on regularly even on slight inclines. What size tires? What is your axle gear ratio?
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post #3 of 6 Old 06-09-2018, 09:37 AM Thread Starter
Markpenn
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Thanks for the quick reply. Tires 33x12.5x15, ratio 3.73
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post #4 of 6 Old 06-09-2018, 10:07 AM
biffgnar
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Completely normal. The "right" gearing for 33s and the 42RLE is 4.88 IMO.
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post #5 of 6 Old 06-09-2018, 10:16 AM
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turn off the o/d and you will be happier. the 42rle needs super deep gears with larger tires and the engine has no issues running at 3k rpm


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post #6 of 6 Old 06-09-2018, 10:43 AM
Jerry Bransford
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Quote:
Originally Posted by Markpenn View Post
Newbie, 2003 TJ. While going along at I.E., 60/65mph and want to go a little faster or just slight grade, while applying slight throttle, the TJ will shift down somewhat erratically to fourth(?) and even seems like down to third(?). Just wondering, adjustments needed, torque converter going south, etc. It is very annoying. Any input is welcomed, thanks in advance.
First, when you step on it slightly, that just unlocks the torque converter which gives you slightly higher rpms, making it appear it downshifted but it hasn't... it's still in 4th gear which is Overdrive. Stepping on it harder puts it into 3rd.

Your main problem however is that with your 3.73 gears, you're severely undergeared with your 33" tires and 42RLE transmission. That makes the rpms so low that neither your engine nor transmission will perform well. My TJ with the same transmission had 4.88 gears in it when I bought it with 35's and it was undergeared even with 4.88. It downshifted erratically and the whole drivetrain struggled on even minor grades. I regeared it to 5.38 in December and it made a dramatic (!) improvement in its highway traits and manners. Even my mpg went from sub-12 mpg to nearly 15 mpg after installing the 5.38 gears. It downshift more easily now and the whole drivetrain just seems very noticeably "happier". And actually, I'd probably go with 5.13 if it were my TJ. And those ratios are recommended because of their good highway rpms and traits, we're not recommending those ratios just because they also work so well offroad. They will NOT produce excessive highway rpms.

I'd seriously consider regearing to 4.88 for your 33" tires as suggested above by Biffgnar. If you did that, you'd be amazed at how much better the Jeep works in all conditions. Your engine is lugging with those 33" tires and 3.73.

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