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Advice please re knock in drivetrain


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Evening All.

I have knock (possibly better described as a clunk) from the drivetrain when I lift the clutch and the wheels start to move. I can also hear it at low speeds when releasing the clutch after changing gears 2 - 4. Cannot hear it at high speed. The car drives beautifully apart from this.

Could this be the problem?

The play seems to be only in the nearside diff yoke and I cannot detect any play in either side shaft splines or UJ's which are all new.

Can anyone tell me what the problem might be here and what the fix might involve? The diff has not been rebuilt, but CTM replaced the seals and bearings about 5 years ago after which it sat in my garage during my re-build.

Many thanks,

Sean 

 

 

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The most common transmission knock from an IRS TR is from worn universal joints, usually in rear half shafts, sometimes in the prop shaft. Next most common clunk is worn splines in the half shafts.

Nigel

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Sean,

If you press the UJ’s and splines full with grease and still hear the clonk you can eliminate those I think.

Based on the movie (very good) it sounds like the diff.

Waldi

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Sean - if you decide you want to go down the route of a  replacement diff , I have a couple of newly refurbished 3.45 diffs sitting on a shelf, which are surplus to my requirements - have sent you a PM with full details

cheers

Rich

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Thank you all for your input so far.

I'm pretty sure it is not the UJ's as these are all new and greased (including the propshaft). I can find no manual play in the splines on the shafts. I have had them off again to check. When I rock the inner part of the drive shaft only, the play and noise (audible in the video) is still there and as I say above appears to be only in the passenger side of the diff.

3 hours ago, RogerH said:

           Assuming the splines and UJ's are OK on the drive shafts then  it could be excess backlash on the diff crown wheel. I have a similar knock.

 

1 hour ago, Waldi said:

Based on the movie (very good) it sounds like the diff

Roger, if its excess backlash, is this something that can be lived with, or is damage being done by ignoring it? What is the fix?

Thanks again.

Sean

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Diff back lash. A bit worse than usual but I wouldn't be spending a lot of money or time fixing it yet. 

These cars are not perfect, trying to make everything perfect will cause a lot of heartache and financial pain.

Edited by John McCormack
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Hi Sean,

              as you know it is there then try and drive around it. I shall live with mine through the summer and think about a 4th rebuild in the autumn.

On start up lift the clutch slowly to engage drive. Changing gear shouldn't be a problem. Slowing down can cause backlash so I dip the clutch.

As mentioned by GT6M (Markus) even a rebuild may not solve it.

 

Roger

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23 minutes ago, RogerH said:

Hi Sean,

              as you know it is there then try and drive around it. I shall live with mine through the summer and think about a 4th rebuild in the autumn.

On start up lift the clutch slowly to engage drive. Changing gear shouldn't be a problem. Slowing down can cause backlash so I dip the clutch.

As mentioned by GT6M (Markus) even a rebuild may not solve it.

 

Roger

+1. Smooth driving almost eliminates the noise and you can still give it a gut full of throttle when in gear.

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10 hours ago, John McCormack said:

Diff back lash. A bit worse than usual but I wouldn't be spending a lot of money or time fixing it yet. 

These cars are not perfect, trying to make everything perfect will cause a lot of heartache and financial pain.

I agree with John, they all do this to a lesser or greater degree and its probably very difficult/expensive to eliminate entirely.

Daz

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  • 1 year later...

Afternoon all.

I am following up on this post from last year where I described my "Knock". See video in first post above.

I still have the knock and if anything it is getting worse. On Saturday I allowed the car to freewheel downhill with the engine off and noticed that I could hear a knocking noise just from the revolution of the wheels. Today I jacked the back up to investigate and isolated it to the rear wheels. Definitely coming from the diff.

I would welcome everyone's opinion on whether this is something that needs attention soon or if it still something that I can "drive around" Is this a major fix or is a reconditioned diff a better option?

You can hear it in the video link below.

Many thanks,

Sean

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Had exactly the same on my last 6. Jack up the rear on axle stands and hold the prop shaft with some gripping gloves and turn each way and see what you hear, then do the same on the drive shafts, you may find its is a UJ, or worn splines on the shaft or prop. 

I found the rear wheel could be turned three quarters of an inch each way without moving the diff. The whole lot was replaced which I obtained from Prop Tech. it is just a case of elimination, good luck. 

 

Rob

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Hi Sean,

that is a bu66er indeed.

Isolate each drive shaft ;- somehow lock the output from the diff so that both UJ's and the wheel can be wobbled back and forthwith nothing from the diff at all.

Any noises then you have found it.

If the drive shafts are good then it must be coming from the Diff.

if you need to take it off and get it sorted these people were high;y recommended 2 years ago in doing a TR6

http://www.testransmissions.co.uk/tes-transmissions-contact-us-2008.html

 

Roger

 

 

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4 hours ago, RogerH said:

Hi Sean,

that is a bu66er indeed.

Isolate each drive shaft ;- somehow lock the output from the diff so that both UJ's and the wheel can be wobbled back and forthwith nothing from the diff at all.

Any noises then you have found it.

If the drive shafts are good then it must be coming from the Diff.

if you need to take it off and get it sorted these people were high;y recommended 2 years ago in doing a TR6

http://www.testransmissions.co.uk/tes-transmissions-contact-us-2008.html

 

Roger

 

 

Thanks Roger,

Any suggestions on ways to "somehow lock the output from the diff so that both UJ's and the wheel can be wobbled back and forthwith nothing from the diff at all."?

I'm sure you've done it before :D

Cheers,

Sean

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Hi Seran,

never done this but I'm sure it is do'able.

Very large Mole grip or G clamp holding onto the output flange and another clamp hoilding that against something solid.

Report back on the lash up engineered design you conceive.

 

Roger

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15 hours ago, RogerH said:

Report back on the lash up engineered design you conceive.

Roger

Roger and all,

I managed to engineer a diff immobilisation tool using the very latest nano-technology. See the photo below.

The resulting immobilisation is, I would say, 99% rather than 100%, but......

With the diff immobilised, my offside wheel has zero play. There is some play in my near side wheel as captured in the video linked here. This is very little compared to the movement and noise I have with the diff unleashed as can be seen in my two earlier videos above.

What do you all think on whether my problem is diff or driveshaft or both?

Many thanks,

Sean

 

 

Diff Immobilisation pic.jpg

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As your subtle immobiliser has removed all the play then the becomes the prime suspect.

If you can quickly remove it and tie up with a local diff builder then go that way. Otherwise wait for the autumn/Winter and get it sorted then.

Mine has a clonk when taking up drive and I can live with that. Your knocking noise is a worry.

Roger

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2 hours ago, Mark69 said:

Sean, what happens if you unleash the offside diff, leaving the near side. 

Mark,

Thank you for suggesting this. With the offside output shaft released and the nearside one still immobilised, I clearly hear the knocking noise when I spin the offside wheel (ie with the nearside wheel not moving). I think this strongly suggests that the knock is in the diff because

1. The nearside which has some minor play in the driveshaft is not moving

2. I know the offside driveshaft has zero play

therefore the knocking noise cannot be from driveshaft play so must be from the diff.

QED

Thank you all for your help.

Sean

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13 hours ago, SeanF said:

Mark,

Thank you for suggesting this. With the offside output shaft released and the nearside one still immobilised, I clearly hear the knocking noise when I spin the offside wheel (ie with the nearside wheel not moving). I think this strongly suggests that the knock is in the diff because

1. The nearside which has some minor play in the driveshaft is not moving

2. I know the offside driveshaft has zero play

therefore the knocking noise cannot be from driveshaft play so must be from the diff.

QED

Thank you all for your help.

Sean

This might indicate the bearing in the diff is at fault. Is there any grinding noise from the diff near the axle when you spin the wheel? Diff backlash shouldn't give a knocking  when it is rotating, only on take up and back off.

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1 hour ago, ntc said:

Sounds like you may have a broken tooth on the crown wheel 

Yep, that too!

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