12 replies to this topic

[blackbelt1990]

Afternoon all, just finished swapping my final drive and I need to shim the diff. It did have one in but a. I’ve changed the crown wheel and b. the gearbox has dubious history so I don’t believe it was right anyway.

I’ve read online that, for my type of bearing, I should have a clearance if 4 thousands of an inch. I’ve built the diff casing up with no shims and the total space is 27 thousands, so allowing for the 4, I have 23 left that I need to shim up to.

The problem is… minispares only sell 6/10/20 thousands shims, so I either have to go for 24 or 20. Is it better to be under or over?

[Spider]

Just to be clear here, the Diff Bearings needs either 0.001" or 0.004" Pre-load (not end float or 'clearance'), the different numbers here relate to the type of Bearing you are using.

 

To a point, if you can't get were you want to be, it's better to go over than under, but, not too far over. The reality of 'Pre-loading' these Bearings is they are huge and will take loads of pre-loading (or axial thrust), but going too far only flexes the side covers on the diff.

[blackbelt1990]

Just to be clear here, the Diff Bearings needs either 0.001" or 0.004" Pre-load (not end float or 'clearance'), the different numbers here relate to the type of Bearing you are using.

To a point, if you can't get were you want to be, it's better to go over than under, but, not too far over. The reality of 'Pre-loading' these Bearings is they are huge and will take loads of pre-loading (or axial thrust), but going too far only flexes the side covers on the diff.

I should probably check I am measuring this properly then. I’ve got both end covers on and I’m measuring the gap between the bearing and the side cover on the left hand side (looking from the rear).

Is this correct?

Also, by “over” loading, do you mean go for a bigger shim than is required if I can’t get the perfect shim?

Thanks for the reply!

Edited by blackbelt1990, 19 November 2023 - 07:32 PM.

[Shooter63]

I recently shimmed a diff using the RHP bearing which do not have thrust written on them, to double check I asked John Guess ( Guessworks ) what the pre-load should be, he said 0.000 to 0.001 so in your case 0.006 x 3 + 1no 0.010 would be spot on.

Shooter

[blackbelt1990]

I recently shimmed a diff using the RHP bearing which do not have thrust written on them, to double check I asked John Guess ( Guessworks ) what the pre-load should be, he said 0.000 to 0.001 so in your case 0.006 x 3 + 1no 0.010 would be spot on.

Shooter

I’ve got the Thrust type bearing which needs 0.004 of clearance. So I’m thinking if I go for 0.006 x 4, that would leave me with 0.003, better to be too tight than too slack?

[Spider]

 

Just to be clear here, the Diff Bearings needs either 0.001" or 0.004" Pre-load (not end float or 'clearance'), the different numbers here relate to the type of Bearing you are using.

To a point, if you can't get were you want to be, it's better to go over than under, but, not too far over. The reality of 'Pre-loading' these Bearings is they are huge and will take loads of pre-loading (or axial thrust), but going too far only flexes the side covers on the diff.

 

I should probably check I am measuring this properly then. I’ve got both end covers on and I’m measuring the gap between the bearing and the side cover on the left hand side (looking from the rear).

Is this correct?

Also, by “over” loading, do you mean go for a bigger shim than is required if I can’t get the perfect shim?

Thanks for the reply!

 

 

Yes, you'll set (or bias) the diff one way and fit that cover with the gasket (dry !), then fit the other side, with no gasket and measure any gap, if there is no gap, add shims until you get a gap that is your gasket thickness + the preload amount. If you are needing a preload of 0.004" and you only end up with 0.002", then add in the 0.003" shim, which will end up with a preload of 0.005". This is going 'over'.

I think the workshop manuals give a figure to allow for the gasket thickness, but that's on the assumption you are using factory gaskets. After market gaskets vary in thickness, so measure what you are actually using.
 

[blackbelt1990]

I had a horrible thought last night that I was measuring it the wrong way round and I needed to ADD the 0.004 onto the 0.027!

I’m pretty sure I’ve got it nailed now though, time to order some shims!

I already have a 10 on there, so if I order 2x6 then that will get me to 22 in total and I’ll only be 0.001 away from the magic 0.004

Edited by blackbelt1990, 20 November 2023 - 06:42 AM.

[stoneface]

I had a horrible thought last night that I was measuring it the wrong way round and I needed to ADD the 0.004 onto the 0.027!

I’m pretty sure I’ve got it nailed now though, time to order some shims!

I already have a 10 on there, so if I order 2x6 then that will get me to 22 in total and I’ll only be 0.001 away from the magic 0.004

Hi, You keep using the word "clearance" as if you want to leave a gap between the bearing and side cover.

 

Maybe I'm reading it wrongly, but, if this is what you mean then it is not correct. There is no gap. There is interference so the bearing is squashed between the side covers and pre-loaded by 0.001" or 0.004" depending on your bearing type.

 

And don't forget the gasget thickness in the calculation.

 

Sorry if I've missunderstood, just want to make sure you're doing it right.

Edited by stoneface, 20 November 2023 - 10:50 AM.

[blackbelt1990]

I had a horrible thought last night that I was measuring it the wrong way round and I needed to ADD the 0.004 onto the 0.027!

I’m pretty sure I’ve got it nailed now though, time to order some shims!

I already have a 10 on there, so if I order 2x6 then that will get me to 22 in total and I’ll only be 0.001 away from the magic 0.004

Hi, You keep using the word "clearance" as if you want to leave a gap between the bearing and side cover.

Maybe I'm reading it wrongly, but, if this is what you mean then it is not correct. There is no gap. There is interference so the bearing is squashed between the side covers and pre-loaded by 0.001" or 0.004" depending on your bearing type.

And don't forget the gasget thickness in the calculation.

Sorry if I've missunderstood, just want to make sure you're doing it right.

Thanks for the reply, this is what I was looking to clarify earlier!
All the video guides I have watched talk about being able to fit a feeler gauge between that is 0.004 thick. That is what is making me think it’s a clearance rather than a pressure?

[KTS]

it's both;  the clearance is measured and set to ensure the correct preload is applied when the side cover bolts are fastened

[blackbelt1990]

it's both; the clearance is measured and set to ensure the correct preload is applied when the side cover bolts are fastened

So I should be measuring for a gap of 0.004 between the bearing and the side cover?

[KTS]

 

it's both; the clearance is measured and set to ensure the correct preload is applied when the side cover bolts are fastened

So I should be measuring for a gap of 0.004 between the bearing and the side cover?

 

 

No - the gap you should be measuring is between the side cover and the differential housing.

 

Post #6 by Spider covers the basic process, but i'd recommend having a look at the haynes manual if you're not too sure of what to do

[Spider]

 

it's both; the clearance is measured and set to ensure the correct preload is applied when the side cover bolts are fastened

So I should be measuring for a gap of 0.004 between the bearing and the side cover?

 

 

Also add to that 0.004" your gasket thickness and then you have it.

In theory, you could leave the gasket in there and measure between that and the gearbox case looking for you 0.004", but in practice, you'll find that works out very inaccurate.