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-   -   Loss of power in overdrive. (https://www.jeepforum.com/forum/f9/loss-power-overdrive-4435239/)

maintman40 06-12-2021 07:34 PM

Loss of power in overdrive.
 
2004 4.0
Starts and runs good. Wont gain speed in overdrive. Seems very sluggish. New air filter, spark plugs.

Jerry Bransford 06-13-2021 10:38 AM

Your 42RLE's overdrive ratio reduces the engine rpms so much that it will barely accelerate in overdrive. Its OD ratio is .69 so the engine rpms are reduced to 69% of what they were in 3rd gear. To really accelerate you need to get out of Overdrive by either stepping hard on the gas or temporarily switching the Overdrive off.

Something else that will cause a lack of power is having installed larger tires which further reduces engine rpms. Bigger tires can kill performance and the only fix is to regear both axles to a lower ratio to get the engine rpms back up to where they should be.

What size tires are you running?

TheBoogieman 06-13-2021 02:09 PM

You might have 3.07 gears also.

Jerry Bransford 06-13-2021 02:16 PM

1 Attachment(s)
Quote:

Originally Posted by TheBoogieman (Post 41292347)
You might have 3.07 gears also.

X2, your TJ would be a real dog acceleration-wise with 3.07 in the axles.

You should be able to tell what your axle ratio is by looking at the steel ratio tag bolted onto the 9 o'clock position of your diff covers. This tag is indicating a 3.73 ratio inside the axle. No worries if yours says 3.08 or 3.74, the front and rear axle ratios are .01 different on all but Rubicons.

dbbd1 06-13-2021 02:33 PM

Add to that above too, that maybe the transmission kick-down cable (I forgot the name right now) may not be adjusted correctly.

Jerry Bransford 06-13-2021 04:33 PM

Quote:

Originally Posted by dbbd1 (Post 41292359)
Add to that above too, that maybe the transmission kick-down cable (I forgot the name right now) may not be adjusted correctly.

While the earlier 32RH had a TV (throttle valve) aka kickdown cable, the OP's 42RLE is fully electronic/computer controlled and has no kickdown cable.

rsurran 06-14-2021 12:10 PM

My 2003 had 3.07 gears on 33 inch tires. Luckily it was a 5 speed stick. I posted similar to you when I first got it. After I got educated I never ran it in 5th gear (OD) except on rare occasions of flat level roads. Jeep did fine in 4th.

Wheelin98TJ 06-14-2021 12:48 PM

Jerry pointed out the 0.69 overdrive ratio.

In other words, you are only putting 69% power to the wheels when in overdrive.

You are around 130hp at the rear wheels stock and this is around 4,500 RPM. In overdrive you'll put about 90hp to the rear wheels at 4,500 RPM, but you'll never see that RPM in overdrive. 4,500 rpm is 190mph with 3.07 gears or 155mph with 3.73 gears.

Long story short, you're below 90hp at the rear wheels in overdrive.

TheBoogieman 06-14-2021 04:45 PM

Quote:

Originally Posted by Wheelin98TJ (Post 41293161)
Jerry pointed out the 0.69 overdrive ratio.

In other words, you are only putting 69% power to the wheels when in overdrive.

You are around 130hp at the rear wheels stock and this is around 4,500 RPM. In overdrive you'll put about 90hp to the rear wheels at 4,500 RPM, but you'll never see that RPM in overdrive. 4,500 rpm is 190mph with 3.07 gears or 155mph with 3.73 gears.

Long story short, you're below 90hp at the rear wheels in overdrive.

Well that's depressing info. :pout:


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