4L60E Lurches forward between 3rd & 4th gear at times (2004 VY2)

[vk4akp]

Hi guy's,

My 4L60E Transmission has started to develop a bit of a lurch or dump-in effect at times when it shifts from 3rd to 4th gear.
More so when your gliding.
I also notice that when in park with the hand break on you can get a bit of play in the tail shaft (rotating it) that follows through the diff and into the axels.
To me this is not right as the CV's / Uni's should be a solid hold to the rear wheels when the hand break is on.

So my questions are. Is this issue likely to be the rear independent axel uni's? Or could it be the gear box? Maybe shift solenoids etc?
I've tried to Google info on this box and how it works but I haven't found anything yet to explain what solenoids do what for 3rd to 4th shift.

Any help appreciated.

.-.-.

 

[vk4akp]

OK. I've run tuner pro on the car while taking it for a spin. I drove it a little harder then normal and the clunk seems to be coming from the back of the car so I'm now suspecting the LSD diff or the CV's more so then the box.

I'll attach the Log file if anyone wants to have a look and comment.

.-.-.

 

[Tonner Matt]

Hi guy's,

My 4L60E Transmission has started to develop a bit of a lurch or dump-in effect at times when it shifts from 3rd to 4th gear.
More so when your gliding.
I also notice that when in park with the hand break on you can get a bit of play in the tail shaft (rotating it) that follows through the diff and into the axels.
To me this is not right as the CV's / Uni's should be a solid hold to the rear wheels when the hand break is on.

So my questions are. Is this issue likely to be the rear independent axel uni's? Or could it be the gear box? Maybe shift solenoids etc?
I've tried to Google info on this box and how it works but I haven't found anything yet to explain what solenoids do what for 3rd to 4th shift.

Any help appreciated.

.-.-.

I used to own a VX V6 Series II that started doing the exact same thing.
Gave it a transmission service and added a bottle of this Lucas Additive while I was at it.
Can't say whether it was the additive or the service & fresh fluid that sorted it out, but it worked and never done it again.

http://lucasoil.com.au/products/transmission-products/lucas-transmission-fix

That little bit of rotational play you get when turning the tailshaft is just backlash in the diff.
Unless it is clunking/thudding violently or making terrible metallic pinging sounds it is nothing to be worried about....But if you are concerned that something isn't right, by all means get someone to take a look at it for you.

 

[vk4akp]

Thanks. It's not looking like the transmission at this stage. Could be the LSD, CV's, or even mounts somewhere. Once someone looks at the Tuner Pro log's I'm pretty sure it will rule out the transmission not shifting properly .-.-.

 

[vk4akp]

So a bit of an update. I got a friend who's been a mechanic most of his life to get under the back of the car and sus it out.
He said that although there is a small amount of play (in his words normal) there is nothing worn or defective that would cause the issue.
The only thing he did spot is he felt the diff was too hot for the amount of driving done to get there.
He suggested I check the oil level in it. And suspected that it was not full.
So today I will try and get time to drop the oil out and replace it totally.
See what sort of outcome that gives.

I assume the bottom bolt in the housing is the drain plug?​

.-.-.

 

[psycho_smurf]

The most common cause of hard shifts is a low fluid level. Jerky shifts can also be caused by excessive line pressure due to a clog or malfunctioning shift solenoid. If it was the drive shaft or diff etc it should occur on every gear change. Get ya tranny serviced mate.

 

[vk4akp]

Found this last night

https://gobdp.com/blog/why-is-my-transmission-shifting-hard/

Why Does My Transmission Jerk When Shifting Gears?
As we talked about, erratic shifting can be the sign of a transmission problem and that would include jerky shifts. If your transmission shifts too quickly into a gear it will make your car “jerk” or accelerate too quickly on that shift. The most common cause of hard shifts is a low fluid level, so check your fluid level and add BlueDevil Transmission Sealer if it is low. Jerky shifts can also be caused by excessive line pressure due to a clog or malfunctioning shift solenoid.

So low fluid. Or
Excess pressure due to blocked solenoids.

Next effort. Maybe drop the pan, change the oil, and replace all solenoids

 

[vk4akp]

Had to try 5 times retyping that last message before it finally saved.

So doing this one as a separate one.

I also took the car to the local Transmission shop.
They test drove it but didn't make it play up much. (I should have drove).

They suggested end play in the transmission shafts caused by bearing wear.

But I think that's yet another incorrect guess as it only happens between 3-4 change.

He also said no way it can be solenoids. (Conflicts with previous info).

.-.-.

 

[vk4akp]

OK. So just had the car to *yet another* mechanic.

He said there is nothing wrong with the box and that it's some sort of gap / looseness in a mount or joint when coasting the gear change gap allows for a slight bit of "take up" and causes the harsh jump or lurch in 3-4. When under load it's mostly not there so once again this makes sense.
I have wondered this all the way through and it was why I replaced the CV's and axels etc.

It's becoming a pain this thing.

Will now look at the engine mounts, gearbox & Diff mounts, and centre tail shaft bearing surrounding rubber case.
.-.-.

 

[vk4akp]

Looked at the engine, gearbox, & Diff mounts today. All look good. Most have been replaced by the previous owner.
About 1cm of movement / flex in the centre tail shaft bearings surrounding rubber but I am told that's normal.

I came across this today.
http://forums.whirlpool.net.au/archive/1976448

A few interesting points in that thread that have merit and worth exploring.

"Strangely enough in my experience, the decel/accel clunk with 4L60E's (Commodore auto's) in 4th has on quite a few occasions come down to the IAC and/or the throttle position sensor being clagged up, combined with a need for fresh trans fluid. The clunk is a confused torque converter lockup, due to bad info from the above mentioned sensors."

Anyone know a good cheap source for the IAC & TPS Sensors? Are they the same on all EcoTec Commodores? (Mines VY2).

This is something I can investigate with Tuner Pro once I get it going again. (Laptop upgrade / re-install). Have forgotton what config files ADX etc come from where on the net and go to where in the software. ???

.-.-.