Differential bearing replacements

Thank you very much for your help. After reading the original service manual (section about repairing a differential), I have a much better understanding of the topic. It certainly demands a mechanic with a good experience, and who will do every step carefully and correctly.

My biggest constraint in this situation is having a diesel edition. I have determined that differentials from diesel Jimnys have specific transfer ratios to them (3.416 apparently). So no petrol differential is compatible (both differentials have to have the same transfer ratio).

The only consolation is that all diesels have the same differentials, so at least there are no revisions there. I just need to find a DDiS differential.
However, finding a DDiS differential is four times as hard and at least four times as expensive than finding a petrol one. I see petrol differentials going for 70-100 pounds in UK, while in Germany a DDiS differential (if you even find it) is several hundred euros or close to a thousand, depending on the alignment of stars and the period of the moon.


I could replace both of my differentials with a pair of differentials from a petrol Jimny. The casings and spline counts on the connections with the halfshafts are the same as in petrol Jimnys.
However, as far as I know, there are two editions of differentials for petrol Jimnys (with higher and lower transfer ratios - 4.3 and 4.09). Correct? Does anyone know how to differentiate these two types?


In the case of 4.09 diff, my total transfer gear ratio would be reduced by 19,7%.
In the case of 4.3 diff, my total transfer gear ratio would be reduced by 25,8%.

Both reductions are too extreme, unless very large tyres are used to compensate (but then the mechanical stress on the driveline is increased).

For example, in the first case, my RPM at cca 100 km/h in 5th gear would increase from cca 3000 RPM (now) to cca 3600 RPM. The second case is even worse.


Regarding the gearbox, I don't know which model it is (I am eager to find that out, but don't know how). I just know it probably is not R72 because the casing looks very different (I think it is DDiS specific). But I think that the electric transfer box is the same as in petrol Jimnys.

I just pray that my DDiS gearbox does not malfunction one day, because that will be the day when a car funeral will be a cheaper ceremony than a car repair .,.



P.S.
What does this dial indicator measure? What units does it display on its gauge? Is this a dynamometer?

Why didn't you preventively replace the bearings while you had the differential dismantled to install the locker? Or you judged them to be in such a good condition as new?


My mechanic will open the differential on Monday. Then we will know the situation inside. If I am lucky, just the bearings will be worn. But should I preventively replace or somehow refurbrish anything else? Should I replace all bearings regardless if some of them are still good?

What bearing brand to recommend or to avoid (Timken, Koyo, SKF, NGK, etc.)? Most shops over here sell SKF. But some people tell me SKF is not reliable (non-consistent quality)?

Riccy wrote: Yes, Your welcome and more than helpful yourself!

The dial indicator is a simple but precise device for measuring pressure on a pin-point. Below is a link to the one i bought for the job:

www.machinemart.co.uk/p/cm220-dial-test-indicator/

Dail indicators measure distance not pressure usually in 10ths of millimetres but also in 100ths thought the finer the resolution the more expensive the tool. Test indicators are essentially the same but much more accurate and usually don't have as much range of measurement. Typically a dial will have a range of 0to25mm and a test might be 0to10mm. As i understand it from my work in machining.

The diffs are not that difficult to take to bits, but it does need you to be organised with the parts and manuals. When i did the lockers i didnt need to take the input shaft out, hence i took the 'aint broke, dont fiddle' approach to the bearings. I think it might be possible to take that shaft out from the input flange end without taking the whole planetary gear/ring gear apart.

There is a third option for petrol diffs - 3.909, which is what i have. These were fitted to manual petrol M13 jimnys 2000-2005. That would be the closest match to your original diffs. These cost me £160 for a pair in the UK.

To work out the ratio in a diff - divide the number of teeth on the crown gear by the number of teeth on the input shaft that connects to it.

You could also look at swapping the transfer box if ratios need to match better, but you would probably need a custom made prop to link to the gearbox. The 3.909 diffs would have been mated to a stick shift style transfer box with a 1.3 output. the push-button t-box's have a 1.0 output.

11/60 has a much better description of the dial indicator in his post above than mine. Its used to set the 'backlash' on the crown wheel. This is effectively a sort of balancing of the bearings and diff in the housing. If its too loose then you will get noise from the diff, too tight and it will wear prematurely and use more fuel (drag effect). The amount of backlash should be measured before taking it apart, and put back to the same amount when re-installing. This could be the issue you have if the bearings are ok?

I will not bring anything useful into this conversation but I would like to drag out some 100% confirmed information.
You mentioned about swapping over the diffs between petrol and diesel versions.
So, are the diffs fully interchangeable? If there are petrol version axles, is it possible to fit into them diesel version diffs and vice versa ? Is it just plug and play?

I cant say for certain, but would expect them to be interchangeable.

The axle housing will likely be the same in all years/models. the difference will be the tooth count on the crown wheel and corresponding input shaft. For suzuki to make completely different axle casings when they could just swap the two gears would be odd.

The axle case is definitely different between automatic transmission and later manual as my diff didn't fit when I had to replace my original axle case.