Robh727

HeyCherokee Forums,

i was curious on us in talks opinion on some weird shifting I’m occasionally having. Car will accelerate fine and seems to shift well from 1-2 and 2-3. When continuing acceleration from 3-4, car seems to downshift back to 2 and then quick upshift back to 4. Not entirely if it’s actually downshifting and then quickly upshifting but notice, a RPMs drop (upshifting) then quickly jump back up (random downshift) and then quickly drop again (upshifting again). It’s not a crazy fluctuation in RPMs but it appears to be around 200-500. Any ideas?

zj rider

it could be a bad T.P.S. it can cause shifting problems

Noah911

200+/- extra RPMs does not seem like a whole lot of unexpected increased variance to me with how you describe the symptoms.

1 - 2 and from 2 - 3 are perfectly ok.

Sometimes, when getting out of the primary drive gearing, going from 3rd into 4th the overdrive gear, that is the only time when you experience the increase of about 200+/- RPMs or so? A consistent increase of 500RPM is certainly a much bigger increase, but this depends on wether you are stressing the engine? If you were going up a hill or mountain.. or only when in a certain RPM range.. or if towing a heavy load.

I towed 4000Lbs behind my WJ 1,000 miles distance up and down a mountain... I got to know the rev range capabilities of my WJ very well. It is not always a smooth transition between the gears which is completely dependant on the specific conditions and circumstances. Going from 3rd gear to 4th gear is definitely the least well behaved transition. I would easily see a strange dip of maybe 200 RPM to increase maybe 200 above where it probably should have been.. when I was towing all of that weight pushing 70MPH descending down a long mountain hill pass getting the WJ up into the overdrive!

(edited to add):
It felt kind if like a downshift to me too..

Robh727

Hey Noah,

i appreciate the help. After driving on it for another day or so, the feeling is almost more of a hiccup/flare. Shifts great going from 1-2 and 2-3 but as you mentioned the 3-4 is primarily where I feel a half second “hiccup”. Almost seems as if the shifter is confused and wants the RPMs to bump 100-200 more to hit the desired shift point. There is no clanking and this is under normal drive. All other gears feel good and don’t notice any delayed engagement going from park to reverse or reverse to drive.

Edit: Saying half second is even generous. It’s too short to time, but it’s very quick and can notice the RPM change on the tack

Noah911

I have noticed similar behavior from my 4.0 WJ too. Only when going from 3rd to 4th gear did I ever really notice it. It was not super exagerated, but enough so to take notice. Not often.. I could duplicate it when I was on a mountain pass road, a more abrupt transitioning from 3rd to 4th gears with slightly abnormal RPMs at around 65 to 70mph towing a heavy load. In normal driving type of situations just around town or so, it does not noticeably do this. It has occasionally developed the same erratic behavior when in cruse control at 65mph+/- when it is cresting hills, and when it is descending higher-speed declines.

Robh727

Did you do anything to try and diagnose it or just keep cruising? I’m just concerned whether this leads to a bigger issue.

Noah911

I didn't ever do anything about it. If it was big enough of an issue to me, or if it was to ever develope into a consistently worsening type of trouble, having increased worrisome symptoms.. I would probably want to investigate more into the issue.

I think all of our vehicles.. even when they are brand new, they all have multiple different variances throughout and between them. It seems all of our vehicles also have a certain amount of 'normal-abnormal' qualities associated to them with how they operate - and, vehicle specific oddities about them too.

There is soo much happening in our vehicles electronically! Even in small electrical circuits.. Electricity can sure do some very unusually abnormal and unpredictable things... For instance...

To help things. If it has been awhile? Passively flushing in new transmission fluid might be a helpful thing? It would only serve to help with assisting to make a more smooth transition between the gears in the transmission with their transitions.

Air-flow factor will have an effect on the transmissions transitions with enough significance too. Clean good flowing engine air-filter of course. Also, carbon building up in the air-intake system may have the ability to effect how the Jeep operates too, when it is transitioning from the 3rd to 4th gears.

Having a healthy air-intake system & having clean and good fresh transmission fluid introduced into the transmission. To start with.. These two things may help with alleviating the severity of your transmissions transitioning shifting characteristics from happening, for when you are going into the overdrive gear.

Robh727

Any other suggestions?

Noah911

I was thinking about this. I know I could feel it there. It was a little exagerated because I was towing a ZJ behind my WJ at the time, and I was traveling that way up and down mountains.

I tested it under normal conditions. You could try it too, and compare..

Take your 4.0 WJ up to three thousand rpm's on the tachometer.. while in primary drive gearing the 3rd gear out of overdrive. Then, put it in overdrive gear. See what happens?

Mine first increases in rpm's about 175 - 200 rpm's immediately after putting it into the overdrive gearing - the 4th gear. Then, it drops down from there at about 3200 rpm, to about 2400 rpm, for just a split second, then drops a little more settling in at about 2200 rpm in 4th gear going about 70 mph. This all happens in maybe just barely over a second of time.

(edited to add):
Sounds like to me, in my above results - there are mynute computations happening just after engagement, and just prior to finishing the transition, in order to make the adjustment from primary drive into overdrive... Sounds normal.

Noah911

Yes. If your spark plugs are getting older and haven't been checked lately? You could put in new ones gapped correctly. If their performance is degraded, it will have a cumulative effect. Also, the fuel system is in good condition. A new fuel filter may help. Verify appropriate fuel pressures. A bad injector or dysfunctional injectors in general could exaggerate any symptoms. All of these will add cumulative effect.

(edited to add):
A faulty oxygen sensor could have enough effect to skew the air/fuel ratio too, which could exagerate symptoms too. Except, I think you may have other different noticeable symptoms also, with a bad O2 sensor?

dave1123

Sounds to me like it's going into and out of lock-up. That makes a difference of around 200-300 rpms. Apparently the PCM doesn't like the sensor readings it's getting after the 3 to 4 shift, so unlocks the convertor until it's satisfied with the power levels, then engages it again.

I've also had the problem where the transmission can't decide which gear it wants when entering on a ramp into traffic when I request more power. I push the throttle down some and it struggles, I give it a little more and instead of dropping to 3rd, it drops to 2nd and roars for a second, then goes to 3rd. I've gotten so fed up with it I generally manual shift it at those times. Adjusting the throttle shift cable doesn't seem to help it decide either.

Noah911

To bounce off from what Dave is saying...

The torque converter is a type of fluid coupling, which allows the engine to spin somewhat independently of the transmission. It is responsible for pressurizing automatic transmission fluid, a pressurization that supplies the force necessary to shift transmission gears.

I think he may be right...

Robh727

Is the general issue with stated above a lack of transmission fluid?

Noah911

I don't think low transmission fluid would really cause the issue.

First of all - outside of the 247 transfer case.. even though all of the transfer case's use atf fluid in them, they are not interconnected with the transmission in any way with its transmission fluid pathways. The torque converter however, it is interconnected to the transmission and to the transmission fluid pathways. The torque converter utilizes atf fluid as well.

From what I understand, the most common symptoms that result from having low atf fluid volume level in the transmission is generally going to be slippage and overheating.

It is a good point to make.. Verifying the proper atf fluid level should be a high priority item.

Robh727

Here’s a good YouTube video of what’s going on: . This video is a tad bit of an exaggeration, but the RPMs are acting in such a manner.

I appreciate the help!