Differential plate angle tooth replace

Hello everyone,

due to damage to the bevel gear of the rear axle drive, I had to replace the bevel and crown gear.
I noticed the damage through the typical howling noise when changing loads. Running line approx. 160TKm, the oil was changed regularly - why did the damage occur now...?

Scuffing on the bevel gear - no signs of scuffing on the ring gear, but increased roughness of the tooth flanks.
[Linked Image from up.picr.de]

So I've delved deeper into the topic again and would like to pass on some information to you....

The axle drive on the Daily is a hypoid gear, as is usual with rear-wheel drive vehicles. This means that the axis of the bevel gear shaft is lower than that of the ring gear. (positive axis offset)
Advantages - smoother running, higher load capacity due to the larger bevel gear, more teeth are engaged at the same time, the lower position of the cardan shaft is advantageous in cars.

Disadvantage - due to the stronger sliding movement of the teeth, there are higher friction losses (efficiency), higher demands on material and lubricant (> hypoid gear oil)

The toothing on the IVECO is of the Klingenberg type, ie the tooth backs have a constant width.

Bevel and ring gears are always replaced as a pair (they have a pairing number) and are only available for the 4x4 from IVECO with ET 7170858, 


Bevel & ring gear and measuring dummy
[Linked Image from up.picr.de]

In addition, if you use it cpl. & want to do "right" :

- 2x tapered roller bearings bevel gear shaft 42471125 (old 7162215) original from Timken: HM803110 - inner diameter: - 41,275 mm, outer diameter: 88,900 mm, tot. Width: 30,163 mm
- 2x tapered roller bearing differential/ring gear shaft 1905216 (old 7164410) Timken original: Y32014X - Inner diameter: 70 mm, outer diameter: 110 mm, tot. Width: 25 mm

- the Simmerring on the flange (12) - has the IVECO Et Nr 40101693 (~50,-€) is from Corteco and since the article Nr 12015770B - dimensions 90mmx60mmx13mm

- the big nut on the flange - IVECO ET 7162213

- if necessary, the shims for the bevel gear shaft (2 sets in increments of 0.025 mm)
- if necessary, individual shims on the ring gear (in increments of 0.05 mm)

Adjusting/screw ring for the bearing preload of the differential housing

[Linked Image from up.picr.de]

and on special tools:

the dummy bevel gear shaft IVECO ET 99370309 (or try instead of measuring)
Dial gauge with holders
Outside micrometer for measuring the adjusting discs
Puller (separating knife)
3/4" nut 36mm
friction coefficient or Drag torque meter
counterholder for cardan flange - self-made
tool for locking the adjusting ring/screw ring - self-made
torque wrench (min.450Nm)
spotting paste

The torque on the picture is too small with 350Nm, I used a larger one - 3/4" 80cm to 750Nm.

[Linked Image from up.picr.de]

As a comparison value, I have/wanted to measure the existing drag torque of the old axle drive before disassembling it. However, this was so small (approx. 0.3Nm) that it was irrelevant for the new setting. The backlash between the bevel gear and the crown gear was now too large.

[Linked Image from up.picr.de]

The process -

drain the oil to remove, unscrew the cardan shaft at the flange, loosen the nut on the flange, which is not easy with the axle installed, since it is VERY tight (tightening torque 450Nm). To do this, I blocked the flange with a tool and operated the toggle of the 3/4" socket with a jack.
Remove the cover from the axle housing and unscrew the two bearing brackets. Unlock the bearing preload adjuster and continue screwing towards the diff to relieve the bearings. Now the diff together with the ring gear should be removed. But that didn't work because the inner ring of the right bearing was too tight on its seat. So I had to drive the bearing, which will be replaced anyway, inwards (left) with a mandrel until there was enough play, now I could remove the cpl. take out the unit. You should not mix up the adjusting and shim washers.
The bevel gear shaft can now also be easily removed, together with the spacer sleeve and the small shim. Lever out the Simmerring at the flange and drive out the two outer rings of the tapered roller bearings with a mandrel. I have a brass pick so as not to damage anything. The inner bearing ring also has a shim and a large shim.

When making the settings / measurements, various default values ​​must be achieved

- the axial installation position of the bevel gear shaft (adjusting washer) > measurement > calculation
- the correct preload of the bevel gear shaft bearings (adjusting washer) > friction value 1.2 - 2.4 Nm
- the correct preload of the bearings of the Diff housing (screw ring) > friction value 2 - 2.8 Nm
-the axial installation position of the diff housing / ring gear (adjusting washers)

resulting in the backlash from ring gear to bevel gear (0.15 - 0.20 mm) and the contact pattern > how/where the teeth touch.

So if you follow the IVECO repair instructions, the strength of the large shim for the axial alignment of the bevel gear shaft is first determined with the help of the dummy bevel gear shaft. You use the dummy because its bearing surfaces are slightly undersized and the bearing inner rings can be removed and installed for the measurements without any problems.
This is quite tricky, because you have to zero the dial gauge to the holder base and you need a VERY flat surface for this. (exact procedure in the guide)

built-in dummy
[Linked Image from up.picr.de]

dial gauge on the dummy
[Linked Image from up.picr.de]

The current bearing preload (coefficient of friction) is determined by installing the dummy shaft and tightening the flange nut (450Nm) and, if necessary, by exchanging the small Shim adjusted to the desired 1.2 Nm to 2.4 Nm.

Bevel gear shaft shims 

[Linked Image from up.picr.de]

Friction measurement
[Linked Image from up.picr.de]

Now the diff can be installed with new ring gear, new bearings and old shims. The bearings are preloaded with the screw ring according to the guideline and the backlash from the bevel gear to the crown gear (0.15 mm to 0.20 mm) is determined with the dial gauge. Depending on the deviation, the diff with the ring gear is removed again and installed with other shims and measured again.

If it's correct, the total friction torque can be measured. Here the guide gives an incorrect value of 20 Nm to 28 Nm. That can't be, since the bearings of the bevel gear shaft should have 1.2 Nm <> 2.4 Nm and those of the diff 2 Nm <> 2.8 Nm. If you want to measure the total friction torque on the flange, you have to take the ratio of 5.22 into account. Only the friction torque from the diff bearings has an effect divided by 5.22. So, for example, at min. 1.2 Nm + (2 Nm : 5.22) = 1.6 Nm (or at max. 2.4 Nm + (2.8 Nm : 5.22) = 2.9 Nm.

If backlash and coefficient of friction match, you should definitely check the contact pattern. That is, how the teeth roll off each other. To do this, the teeth of the ring gear are coated with spotting paste. Then the crown wheel is braked strongly (e.g. mounting lever between crown wheel and housing) and the bevel gear shaft is turned on the flange. This results in the imprints of the bevel gear tooth flanks on the ring gear tooth flanks. This should be approximately in the middle of the teeth.

[Linked Image from up.picr.de]

If the contact pattern is correct, you're done ;-) and can secure (caulk) the adjusting ring on the diff and the flange nut.

If not, the installation position of the ring gear or bevel gear shaft must be corrected accordingly :-(

Leave a comment

Please note, comments must be approved before they are published