Excessive engine/gearbox movement (1 Viewer)

[DeeDogga86]

Hi Team,

this is my first thread in this forum so please be gentle if I may have missed a thread that deals with my issues already. I have been soaking up all the very valid information on this forum far a long time and have found great help so far.
However for the issue that I am dealing with atm I am struggling to find specific information hence why I start this thread.

I own a 1995 VX Limited 24V 1HDFT Auto A442F Jap import. I live in New Zealand and are a mechanic by trade ( just to outline that I am mechanically minded )

My issue:

When driving and slowing down for an intersection and coming to a full stop ( gentle but constant braking till full stop ) I keep my foot pressed on the brake pedal. When I lift my foot of the brake to take off again I then feel this very hard forward knock in the auto gear lever. Same scenario knock can also be caused when coming to a full stop and changing into neutral rather then taking the foot of the brake, gear lever will then again knock forward.
The knock can be felt going through the entire vehicle and is very harsh and concerning.

Same knock can be felt when driving under slight acceleration when shifting from 1-2 nd gear or when downshifting from 3rd OD into 3rd under acceleration.
This knock is a very harsh and hard knock that is as mentioned above very concerning and does not feel normal or to be tolerated.

Things I have checked so far:

- Adjusted line pressure correctly as per FSM, no flaring between gears. Trans shifts fine under full acceleration or when coasting through the gears.
- changed trans fluid
- checked gearbox mount ( removed it and checked for cracks or separation) OK
- checked engine mounts - could see what I thought was excessive sideways movement when loading up the drive train when stationary and in gear, swapped mounts with new ones, same movement persists
- removed drive shafts and check unis and slip joints, cleaned and greases slip joint's
- change every single bush on suspension with new rubber bushes

Probably forgot other things I have done and checked too.

The fact that the gear lever is moving indicates to me that the engine/gearbox is still moving in it's mounts as the gear lever isn't attached to the trans via cable but mechanical linkages hence why it is able to move it.

The big question is > Why and what does create the force to move the engine that much<

Really hoping I will find fellow enthusiasts that have dealt with this issue and came up with a fix as I am pulling my hair out over this and can't figure it out for the life of me.

 

[Marco Lau]

engine mount, tranny mount.

 

[DeeDogga86]

engine mount, tranny mount.

If you read my post carefully you can see that I have already replaced those.

 

[Marco Lau]

You didnt say replace tranny mount with new... just inspect?

 

[Feistl]

As much as it is a pain, pull the front driveshaft and try driving around with the centre diff locked. (If you have the button you can do it in high range, otherwise you’ll have to do it in low range).

just the thought process is there could be a lot of slop in the front end, and the loading/unloading is causing the clunk. So could be worn CV joints or even a broken axle plate. By running it in RWD you can rule out it being a front end issue (and it doesn’t take that long to pull the driveshaft).

it’s also possibly worth testing in low range 4WD anyway...

 

[DeeDogga86]

As much as it is a pain, pull the front driveshaft and try driving around with the centre diff locked. (If you have the button you can do it in high range, otherwise you’ll have to do it in low range).

just the thought process is there could be a lot of slop in the front end, and the loading/unloading is causing the clunk. So could be worn CV joints or even a broken axle plate. By running it in RWD you can rule out it being a front end issue (and it doesn’t take that long to pull the driveshaft).

it’s also possibly worth testing in low range 4WD anyway...

Hi Feistl,

I should have mentioned that I have a AISIN part time kit installed as well.
So I can definitely rule out any front end slack or damage as it is only driven in RWD on road and 4WD locked center diff when off-road.

When I drive around in low range it only makes the knock a lot worse.

 

[DeeDogga86]

You didnt say replace tranny mount with new... just inspect?

Yes you are correct, engine mounts are new and trans mount has been removed and checked for damage.

Just can't se how a still intact trans mount would cause this issue. If it was separated then yes totally.

 

[BILT4ME]

Yes you are correct, engine mounts are new and trans mount has been removed and checked for damage.

Just can't se how a still intact trans mount would cause this issue. If it was separated then yes totally.

If you have over greased or have binding splines on the yoke of the rear DS, it could be shoving the rear DS into the transfer case, pushing it more than it should.

How much movement are we REALLY talking about here? Mine moves 1/4"-1/2" when torquing on a rock or driving down the highway and on and off the throttle.

If you're talking 1" of movement (2.54 cm for those upside downers...) Then you have more of an issue that needs tracking down.

Otherwise you're in OCD overdrive.

 

[SNLC]

Drive flanges.

Cheers

 

[DeeDogga86]

If you have over greased or have binding splines on the yoke of the rear DS, it could be shoving the rear DS into the transfer case, pushing it more than it should.

How much movement are we REALLY talking about here? Mine moves 1/4"-1/2" when torquing on a rock or driving down the highway and on and off the throttle.

If you're talking 1" of movement (2.54 cm for those upside downers...) Then you have more of an issue that needs tracking down.

Otherwise you're in OCD overdrive.

I have checked for over greased slip joints, which was the case. Only just pulled the shafts 2 nights ago and cleaned them all out spotless and only used sufficient amounts of grease to reassemble, still the issue persists!

Movement is excessive to 1/4"-1/2" of movement. I will go for a drive shortly and try to capture the movement on the gearlever on video just for reference and post it here ( if that is even possible?).

 

[DeeDogga86]

Drive flanges.

Cheers

Can you elaborate a bit more please?
Why would a drive flange cause the engine to twist and move?
When I had the shafts removed I checked for axial play, couldn't fault them.

 

[SNLC]

Can you elaborate a bit more please?
Why would a drive flange cause the engine to twist and move?
When I had the shafts removed I checked for axial play, couldn't fault them.

Sorry I just skimmed your thread. I just got home from a 10hr day in my 100+* shop and am beat having a beer.

I read “thunks” under load or put into gear-shifting which is often drive flanges. They get stripped out and cause thunks when shifting.

Ignore me if this is not the issue.

Cheers

 

[DeeDogga86]

If you have over greased or have binding splines on the yoke of the rear DS, it could be shoving the rear DS into the transfer case, pushing it more than it should.

How much movement are we REALLY talking about here? Mine moves 1/4"-1/2" when torquing on a rock or driving down the highway and on and off the throttle.

If you're talking 1" of movement (2.54 cm for those upside downers...) Then you have more of an issue that needs tracking down.

Otherwise you're in OCD overdrive.

Another thing that I noticed ... even after cleaning and re greasing the slip joint it was next to impossible to slide the joint back together all the way as it was creating a pressure bubble inside the joint, I then removed the grease nipple to allow the air to escape and screwed it back in after. Now when mounting the shaft back into the truck I had to do the same thing again to allow air into the joint as I had to lengthen the shaft to reach the flanges.

If it was the case that the slip joint doesn't allow for enough movement and then pushes back against the transfer case causing the engine to twist and move how would I fix it? As far as I know the slip joint can't be replaced, correct? When there was no grease on the joint it was sliding in and out effortlessly.

 

[BILT4ME]

Another thing that I noticed ... even after cleaning and re greasing the slip joint it was next to impossible to slide the joint back together all the way as it was creating a pressure bubble inside the joint, I then removed the grease nipple to allow the air to escape and screwed it back in after. Now when mounting the shaft back into the truck I had to do the same thing again to allow air into the joint as I had to lengthen the shaft to reach the flanges.

If it was the case that the slip joint doesn't allow for enough movement and then pushes back against the transfer case causing the engine to twist and move how would I fix it? As far as I know the slip joint can't be replaced, correct? When there was no grease on the joint it was sliding in and out effortlessly.

Thinking about frame of reference......

Check your body mounts for loose or broken mounts. Maybe it's the body moving around the shifter........

 

[DeeDogga86]

Thinking about frame of reference......

Check your body mounts for loose or broken mounts. Maybe it's the body moving around the shifter........

Been checking those as well. All are tight and no signs of excessive movement.
I am certain it has something to do with the "roll" of the rear axle and the driveshaft binding and pushing into the transfer case.
I have removed the drive shaft again last night and cleaned it out once more and used a different high pressure grease, also measured the pinion angle on transfer case and rear diff, 1 degree difference.
As I said all bushes on the rear axle are new and genuine, engine mounts are new as well.

I need to borrow a go pro of a mate and attach it to the underbody and check a few things when simulating the issue.

 

[Feistl]

Can you leave the rear shaft out and run in front wheel drive?

 

[DeeDogga86]

Can you leave the rear shaft out and run in front wheel drive?

Yep can do. Will test this as well.
Pretty certain it would eliminate my issue as the rear axle won't be attached to the drive train.

 

[pvhobo]

Check your rear axle for movement/rotation.
As you stop it may rotate forward then rotate back as you pull forward.
Or rear axle link mount bushings?

 

[DeeDogga86]

Check your rear axle for movement/rotation.
As you stop it may rotate forward then rotate back as you pull forward.
Or rear axle link mount bushings?

That is exactly what I think is happening but I don't understand why. I have replaced all bushings on the rear axle, upper and lower trailing arms as well as panhard rod.

 

[pvhobo]

Stabilizing the rear axle will eliminate axle rap.
I have not seen this before, or have not been able to verify this happening, but if the axle rotates forward with enough force, or just enough force to push the engine/trans forward when stopping then when moving forward will allow the package to shift back to stock position which flips the rear diff upward??