1" diff drop Q's

[BigRogers]

1 When your lower your front diff, the rear pinon bearing is running dry.

2 When you check or change your diff oil. The Oil fill is sitting lower then stock and you are actually putting in less oil then the factory specs.

Singtoe you certainly know your way around a runner so consider this a question not a flame.....

I was under the impression that the diff drop actually improved the working angle of the cv's. I figured any sort of reduction in cv angle should help the that stress and wear when lifted. It appears looking thought the assembly of a diff, the angle in which the inboard shaft goes into the diff would not change whether it is stock height as compared to lifted. So reduction of oil getting splashed or bearings running dry seem to be a bit misleading.

This is the notation in the FSM to check the fluid level in the diff:

Based on your second note I am not sure how you could fill the differential lower that what is spec'd as you should fill it up to the filler plug. Right?

I know there are many opinions on this, and have read back though some of the pro/cons stated. But to base diff failure on the drop seems a little excessive when so many factors can be a contributing factor: Age and miles on vehicle, driving style, weather, lack of maintenance.

 

[Singtoe]

You notice that the fill hole is in the front of the diff.

Imagine it lower by one inch.

How can you fill the oil back up to the one inch mark to make it at the right level?


How mileage and age doesn't mean jack on our 4runners. The front diff only gets used when in 4wd or awd. How many miles do you really get driven on the front diff.

You could probably count the number of times the differential has spun.

How many miles are driven off road multiplied by the gear ratio multiplied by the number of times driven in 4wd.


The cv's are constantly spinning but no real actual use though. CV half shafts are replaced mainly for the boots and for some hard core wheelers, the semi occasional catastrophic failure.




Here is the reality. Your CV's see more radical angles just steering lock to lock. Tilting the diff is a moot point.





One other point that I forgot to mention is drive shaft angles.

The universal joints have to be parallel for them to be vibration free.

If the pinion angle is changed, the the drive shaft will cause it to speed up and slow down during its rotation.

The only fix for this is to replace the u-joint with a Double Cardan joint or a CV joint. It lets the drive shaft spin the pinion shaft at the same speed.

 

[sn0wrunner]

Bolts are 8" long.

But yeah I wouldn't do it. Out of the thousands of them sold, nearly 50% of the vehicles have blown up and everyone died. Stay away. Call up anyone that sells them, they'll tell you death is a common side affect and they have hundreds and hundreds of people complain about issues with the diff drops.

In all seriousness, they don't make a huge difference.