4l30e false nuetral 3-4 shift light load.

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4l30e false nuetral 3-4 shift light load.

Postby Larryf » Fri Dec 04, 2020 3:43 am

Hello I've searched to no avail looking for someone with a similar issue. When driving at a slight downhill incline between approximately 35-50mph the transmission will go into neutral and rev freely. Manually shifting into 3 will reengage it as will letting off the gas and letting it slow down. It also seems to me like it doesn't like to shift into 4th readily, I have to accelerate hard and then let off for it to shift sometime. It could be normal though, the vehicle is new to me and my first vehicle with the 4l30e.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Buster28 » Fri Dec 04, 2020 10:09 am

What year and model is your truck?
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Larryf » Fri Dec 04, 2020 2:27 pm

Buster28 wrote:What year and model is your truck?

USA 1997 Trooper, 3.2 single cam 4x4.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Buster28 » Fri Dec 04, 2020 4:51 pm

In 4th, 3rd and 2nd gear the rear wheels are connected to the engine by the torque converter so there is limited engine compression braking. In Drive 1st, the sprag unidirectional clutch inside the transmission can unlock disconnecting the engine from rear wheels allowing the vehicle to coast to a stop. However, in L (Manual 1st gear) the 3rd clutch is applied, the sprag does not unlock so there is engine compression braking in L.

The transmission cannot shift into Neutral unless you manually place it in Neutral so it is unclear what is happening from your description.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Larryf » Fri Dec 04, 2020 5:15 pm

Under light load, slight downhill constant speed, the transmission will "shift" into a "false neutral" meaning the engine is not connected to the wheels, I can rev it freely. I believe this is happening when the transmission would normally shift to 4th as when I manually select 3 it engages into 3rd gear, usually around 2500-3000 rpm. This never happens when accelerating or under normal load such as flat ground or on the frewway.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Buster28 » Fri Dec 04, 2020 5:56 pm

To shift from 3rd gear into 4th gear the Overdrive (4th) clutch is applied and the Overrun Clutch is released. When this happens the planetary gear set inside the overdrive section of the transmission assembly shifts from a 1:1 ratio to a 0.723 : 1 ratio. With the transmission in 3rd gear (1:1) and the overdrive section operating at a 0.723 : 1 ratio the overall ratio is 0.723 : 1 which is the 4th gear ratio. However, if the Overrun Clutch releases and the Overdrive (4th) clutch does not apply there is nothing driving the transmission input so the transmission is effectively disconnected from the engine. What happens when your cruising in 3rd and get moving fast enough to shift into 4th gear?
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Re: 4l30e false nuetral 3-4 shift light load.

Postby 02Axiompower » Mon Dec 07, 2020 8:19 pm

I have a 2002 Axiom 4x2 with the 4L30E trans and had the exact problem you describe. It would go to shift into 4th, but would "miss" the gear and go into a "neutral state."

I do not have the problem anymore and I didn't do anything except change fluid and filter multiple times using Valvoline Dexron III ATF in the blue jug.

I'm not exactly sure if it was the old, unknown brand of fluid itself that was causing the problem, or that the fluid level was causing the problem, but after changing fluid a few times and using the Valvoline in the blue jug, at the proper level, the problem is gone. It shifts perfect now, not one little hiccup.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Larryf » Wed Dec 09, 2020 3:56 am

Buster28 wrote:To shift from 3rd gear into 4th gear the Overdrive (4th) clutch is applied and the Overrun Clutch is released. When this happens the planetary gear set inside the overdrive section of the transmission assembly shifts from a 1:1 ratio to a 0.723 : 1 ratio. With the transmission in 3rd gear (1:1) and the overdrive section operating at a 0.723 : 1 ratio the overall ratio is 0.723 : 1 which is the 4th gear ratio. However, if the Overrun Clutch releases and the Overdrive (4th) clutch does not apply there is nothing driving the transmission input so the transmission is effectively disconnected from the engine. What happens when your cruising in 3rd and get moving fast enough to shift into 4th gear?


Thank you for responding, you are very helpful. Now that I know this I've have been paying attention very carefully to how it shifts. I haven't driven the Trooper much so I haven't gotten to replicate the issue since the first post. however seems to shift normally all gears, I can see the torque converter lock up under throttle and then unlock when I coast on the freeway which all seems normal. I do get a pretty nasty chatter when making turns from a stop, which I've only noticed when the trooper is cold. Could this be the limited slip differential, is that normal? I will update with a new post when I replicate the problem, it was doing it pretty consistently when I was driving it more.

Also in case it matters, I did lift and put 35" tires on the trooper shortly after getting it but I noticed all these issues before those modifications as well.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Larryf » Wed Dec 09, 2020 9:38 pm

I drove it more, the "chattering" happens warm or cold when I accelerate hard from a stop, straight or turning, at about 2500rpm a car length or two from the stop. I can't seem to repeat it unless I come to a full stop.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Larryf » Sat Dec 19, 2020 1:38 am

I can replicate the issue reliably. Approximately 35mph when on a slight downhill, just fast enough with no throttle and it will shift out of 3rd but not into 4th. Manually selecting 3 engages 3rd gear, back to d and it goes back into the false neutral. It will naturally go back into 3rd if I slow down enough or if I give it enough throttle it will rev freely until it shifts into 1st.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Buster28 » Sun Dec 20, 2020 9:37 am

Does the truck ever shift into 4th gear and stay in 4th when cruising down the highway?
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Larryf » Fri Dec 25, 2020 1:36 am

Yes it drives totally normally other than the issues stated. Can cruise on the hwy in 4th.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Buster28 » Fri Dec 25, 2020 4:56 am

How good is the compression braking when you shift from 4th to 3rd going down the hill?
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Larryf » Wed Jan 20, 2021 9:31 pm

Buster28 wrote:How good is the compression braking when you shift from 4th to 3rd going down the hill?

Comparable to any other vehicle I drive. I have gotten a transmission check light to flash on two occasions and it started shifting hard when it did. I need to get a scanner that reads transmission codes.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Larryf » Thu Apr 08, 2021 7:49 pm

Bumping this because it's still and issue and I just found something!

This little piece was in the front small transmission pan:
20210408_161255.jpg

And the other bits were caught up here:
20210408_161302.jpg

All together:
20210408_161650.jpg


What is it and could it be effecting my odd shift behavior.

I have just been driving around town in 3 and shifting to D only when I'm on the highway to avoid the issue.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Larryf » Thu Apr 08, 2021 8:04 pm

I have found out it is a thrust bearing. It is talked about in this aricle. Apparently there are two plastic ones and they commonly break.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Buster28 » Fri Apr 09, 2021 6:49 am

It is a selective fit washer, it is used to reduce 2nd and 4th clutch end play.
The color indicates the thickness of the washer.
(0.060 – 0.064) Yellow
(0.068 – 0.072) Red
(0.075 – 0.079) Black
(0.083 – 0.087) Natural
(0.090 – 0.094) Green
0.098 – 0.102) Blue

You have to disassemble transmission to replace the washer. The one you found is for the 4th ("Overdrive") clutch.
Driving around in 3rd prevents the 4th clutch from being applied, so the broken washer could cause of your shift problem.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Larryf » Sat Apr 10, 2021 1:59 pm

What sort of other negative effects do you think will occur without the thrust bearing? So far the truck is at 195000. It's been like this for as long as I've owned it (192k) and probably well before. I'll definitely report back here if it gets worse.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Buster28 » Sat Apr 10, 2021 3:04 pm

Do you think the truck has the original transmission installed?
Have you considered replacing the transmission?
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Larryf » Sat Apr 10, 2021 6:49 pm

I considered it and I will when this one blows up. As long as it works and doesn't get worse I'm not gonna worry too much about it. When it does I'll probably swap in a manual as I don't want to rebuild the auto myself and from reading that article I doubt anyone else these days would rebuild it to the quality and price I'd be happy with. Too many factory "issues" to be remedied like these plastic thrust bearings.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Larryf » Tue May 11, 2021 10:37 pm

Well I overheated it and fried the clutch packs. Got the auto rebuilt, $1500, tax, parts and labor. No more problems.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Buster28 » Wed May 12, 2021 6:05 am

Larryf wrote:Well I overheated it and fried the clutch packs. Got the auto rebuilt, $1500, tax, parts and labor. No more problems.

That is a really good price for a rebuild.
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Re: 4l30e false nuetral 3-4 shift light load.

Postby Larryf » Wed May 12, 2021 1:32 pm

I'm aware, I could barely do a manual swap for that price. That's why I went with it. If anyone is in the Los Angeles area Duarte Transmissions in Pacoima is where I went.
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