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buying a second-hand front diff how do i inspect

Submitted: Saturday, Dec 02, 2006 at 14:33

dirty dirty 4x4

how ya all going i just bought a surf (UNFORTUNATELY) i took it up the road only to discover it a shattered front diff ive priced a second-hand one that seems reasnoble but how do i check it to make sure it doesnt need expensive repairs i have a good basic knowledge of mechanics but havent played with diffs any advice
ThreadID: 39988 Replies: 5
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AnswerID: 208198   Submitted: Saturday, Dec 02, 2006 at 17:48

Bilbo replied:

Dirty,

I haven't done any diff work for years and I've never set up a Toyota diff. But generally speaking check the following:

The diff should be stiff to turn. When you turn the pinion, there should be a fair resistance in the crown wheel. That's the effect of pre-load on the bearings.

Inspect each tooth on the crown wheel for any signs of the case hardening breaking down on the metal surface. This can be seen as pitting or flaking of the metal.

Look for polish marks on the surface of the crown wheel teeth. These are normal but they must be in the correct place on each tooth. This is an indiaction of correct meshing of the teeth between the pinion and the crown wheel. The correct position for this "polish mark" is the centre of the tooth. And the "polish" mark shouldn't extend to the extreme edges of the teeth. The mark should be in the centre.

If possible, wash the gears of any oil and use Engineers Marking Blue Paste on the crown wheel teeth. Rotate the pinion and you should see exactky where the teeth are meshing. This is best done with a screwdriver or tyre lever UNDER the crown wheel whilst applying downward pressure, as if you were trying to liff the crown wheel.

These are just general rules and not Toyota specific.

Bilbo
Remember - "Tomorrow is todays best labour saving device!"
Reply 1 of 5
AnswerID: 208244   Submitted: Saturday, Dec 02, 2006 at 21:29

Exploder replied:

to add to above, Hear is a Drawing to show acceptable gear patterns, once agene it's not Toyota specific.

Ideally if you open it up you would want to check the backlash if you know how.





Cheers.
Reply 2 of 5
FollowupID: 468187   Submitted: Saturday, Dec 02, 2006 at 22:35

Bilbo posted:

Good stuff, Exploder. I forgot about the backlash. There was something niggling at me when I was typing it up,,,,,,,I knew I'd forgotten something.

Bilbo
Remember - "Tomorrow is todays best labour saving device!"
FollowUp 1 of 4
FollowupID: 468416   Submitted: Monday, Dec 04, 2006 at 01:06

dirty dirty 4x4 posted:

thanks for the pictures they will help and if you could let me know how to ckeck the backlash im a quick learner
FollowUp 2 of 4
FollowupID: 468417   Submitted: Monday, Dec 04, 2006 at 01:14

dirty dirty 4x4 posted:

is backlash the free play between the drive shaft diff and or axles
FollowUp 3 of 4
FollowupID: 468467   Submitted: Monday, Dec 04, 2006 at 11:19

Bilbo posted:

Dirty,

The backlash is the "slack" or running clearance between the gear teeth on crown wheel and the pinion. It's normally a very small figure, in the order of two to three thousandths of an inch. This figure varies with different makes.

It can only really be accurately tested with a "DTI" - dial test indicator, but a good diff man or mechanic can make a very good guess just by hand testing.

Some diffs are easy to set up. Others are nigh on impossible to get right. In the latter case, the old Ford Transit diffs were a barsteward to get right. The rest of the car was easy as pie to work on, but the diffs,,,,,,,. We used to buy new ones and chuck the old ones as "too much messing around".

Bilbo
Remember - "Tomorrow is todays best labour saving device!"
FollowUp 4 of 4
AnswerID: 208247   Submitted: Saturday, Dec 02, 2006 at 21:38

Member - DOZER replied:

open it up and look for damage....best way, feel the backlash for minimal amounts, use common sense, but most importantly, check the ratio is thesame as what you have in there now.....there were a few dependant on model, motor etc....seen a few diffs on ebay for the front of IFS lux/surf/etc.....

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Reply 3 of 5
AnswerID: 208532   Submitted: Monday, Dec 04, 2006 at 17:35

G.T. replied:

Hi dirty, you can also get backlash from too much clearance between the `axle ` and ` spider ` gears in the crownwheel carrier.
These gears have thrust washers and they in time ( read distance travelled ) wear and let the gears move slightly out of mesh thus creating backlash. Worth checking, they will not cost a fortune , worth replacing if worn. Regards G.T.
Reply 4 of 5
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AnswerID: 208682   Submitted: Tuesday, Dec 05, 2006 at 09:34

dirty dirty 4x4 replied:

thanks for all your help i think im on yhe right track ill let you know how it works out
Reply 5 of 5