Why my ZJ won't see redline while acceleration? - JeepForum.com
 
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post #1 of 9 Old 06-30-2020, 12:12 PM Thread Starter
delmanciomio
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Why my ZJ won't see redline while acceleration?

Hello,
My 97 5.2 ZJ revs beyond 5000rpm in Neutral but when i try to accelerate wide open throttle it shifts about 3500rpm and this will not give good performance. Why this is happening ? What regulates rpms before shifting?
Thank you

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post #2 of 9 Old 06-30-2020, 12:22 PM
Timo_90xj
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Adjust your throttle valve cable. If it is too loose, transmission will shift at way too low rpms. Even with a properly adjusted TV cable, V8 shifts at around 4750-5000rpms, and I'm pretty sure I6 does the same.
If you want it closer to redline, use manual shifting. Installing a shift correction kit helps, installing Sonnax ZIP- kit improves shift behavior and addresses various other valve body issues.
There are other possible causes, but it's easy to start with the TV cable.

My niner redlines at 6000rpms, WOT upshift at around 5850. Not stock, has a custom tune. Magnum sounds pretty damn good at 6k

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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post #3 of 9 Old 06-30-2020, 02:09 PM
zjosh93
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My 93 would always shift at the redline. I think I just had the TV cable a touch on the tight side of the OEM adjustment. I think it shifts a little lower with the new transmission, but my sister is the primary driver now, and she doesn't drive like me.
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post #4 of 9 Old 07-01-2020, 04:25 AM Thread Starter
delmanciomio
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Yes its loose, can you tell me how can i make it tighter, i am new to car and i want to learn from you guys
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post #5 of 9 Old 07-01-2020, 05:19 AM
Zilliver
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Remove the white clip holding it, tighten it so it will start to move as soon as the throttle valve is moving. Then go for a test drive, if needed adjust it again, but do it in small steps.

Dont make it too tight - no up shifts

Dont make it too loose - very quick shifts all the time in low rpm.

98 Grand Cherokee 5.9 - daily
95 Grand Cherokee 5.2 - offroad
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post #6 of 9 Old 07-01-2020, 07:29 AM
Timo_90xj
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Basically the throttle valve cable should be tight with the throttle pedal pushed all the way to the floor.
To adjust, CAREFULLY (!!!) remove the TV cable endclip (ball socket) from the throttle linkage ball. Then have a helper push the throttle all the way down; adjust TV cable length so that cable pulled tight the ball socket is centered on the linkage ball. Release throttle and re-install cable.
FSM instructs adjusting the TV cable with the throttle plate closed and aligning the cable end socket to within 1mm (0.040") of the throttle linkage ball stud.
Both methods work, but I prefer adjusting @ WOT to ensure highest possible line pressure at WOT upshifts.

Whichever method you use, after adjusting go for a test drive - if it upshifts at full throttle ~5000rpms you're good to go; if it doesn't shift loosen the adjustment a little. If it upshifts a way too low RPMs, tighten the adjustment a little.
Your aim is to have the cable as tight as possible with the tranny still upshifting @ WOT.


If valve body/ transmission has internal leakage issues or sticky valves, tired pump that doesn't provide high enough pressure, TV cable adjustment won't necessarily help at all.
If TV cable adjustment doesn't make a difference, I'd highly suggest doing pressure tests per FSM.

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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post #7 of 9 Old 07-02-2020, 05:56 PM
norconick
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yes like everyone else has said you have to be delicate. The little white U clip keeps the whole adjuster locked together and its probably quite brittle by now. The first time I adjusted mine I did like half centimeter increments and that was way too much. Seriously I'd go like a millimeter at a time once you've got it so it'll shift between 4500 and 5000 like it should. You can feel the difference in shift harshness under light throttle with 1 mm adjustments.

I can make you a little video if you haven't already found one

'98 ZJ 5.9 Limited -- 284k kms
'08 Escape Hybrid AWD -- 532k kms
'04 VW Jetta TDI -- 408k kms
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post #8 of 9 Old 07-02-2020, 05:58 PM
norconick
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Quote:
Originally Posted by Timo_90xj View Post
My niner redlines at 6000rpms, WOT upshift at around 5850. Not stock, has a custom tune. Magnum sounds pretty damn good at 6k
Do you have a cam in it? With the stock cam and stock intake manifold the horsepower drops off fast after about 4000 rpm on mine

'98 ZJ 5.9 Limited -- 284k kms
'08 Escape Hybrid AWD -- 532k kms
'04 VW Jetta TDI -- 408k kms
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post #9 of 9 Old 07-02-2020, 10:18 PM
Timo_90xj
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Quote:
Originally Posted by norconick View Post
Do you have a cam in it? With the stock cam and stock intake manifold the horsepower drops off fast after about 4000 rpm on mine
Cam, heads, intake manifold, throttle body & exhaust have all been upgraded along with a custom tune from Flyin' Ryan.
...and yes, both the 5.2 and 5.9 as stock don't really go anywhere after about 4500rpms especially with a stock PCM flash.

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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