Dementor Center diff problems

[Kromeczek]

Hello, I bought used dementor as a roller, put my own electronics, almost everything works fine, car is a beast but i have 2 problems with center diffrential. Center diff have metal 7075 case, new cups and bearings, gears and spur gear are in good condition.
Firstly diffrential locks itself under load. After rebuilding everything seems to work fine, 0 grinding, smooth but as soon as load from drivetrain is applyed something inside is causing it to jam. So i tested it in my hands bit more and i noticed that when i twist diff holdnig by cups everything is ok on both direction, but when im holding by spur gear and try to twist by cup something is jamming. And that jamming is not like bit of grinding but like sudden lock after while without any prior signs. Internal gears looks fine, no wear on teeth, no shards etc.

Second problem is Centre Diff Bulkhead flex at load, part nummber C-00180-018. This hole for bearing in the middle seems to be larger than it should and bearing have to much space there no matter how tight i screw down 2 pieces. As a result when load from pinion gear is applied entire diff goes 2-3mm up in this place but stays in place at the other side where its mounted to motor mount. Then spur gear is rotating unevenly causing damage on itself and pinion gear. At first i thought that plastic bulkhead is old and give to much flex, bought new one and problem is exacly the same.

What is the answer to this problems? Buying set of diff gears, buying metal diff bulkhead? Diff gears are few euros but metal bulkhead is like 35 euro and could have same problems with hole for bearings to large

 

[DaniC]

The diff shouldn't move in it's place like that! Is the top thing that holds the bulkhead and the motor mount installed? Have you inspected all parts in that area for cracks or bends?

 

[Kromeczek]

The diff shouldn't move in it's place like that! Is the top thing that holds the bulkhead and the motor mount installed? Have you inspected all parts in that area for cracks or bends?

So i managed to find problems causing this. Holes in chasis for motor mount and center diff bulkhead were drilled to close together, probably from factory ( like 1-2mm) and center diff cover (C-00180-015) was bit to long. Screwing down this element caused the bulkhead parts to split in the middle and as a result center diff bearing had to much space. So i fixed this problem by ordering metal bulkhead and new plastic cover. Plastic cover had exactly the same dimensions as the previous one, so that is why i concluded that the problem were holes in chasis to close to each other. But at the end metal touning part fixed everything just by holding everything together much tighter and not spliting apart under load from plastic cover. Without any play car is now quieter, also wear on pinion gear and spur gear stopped

For diff i orderet set of new gears but it did not work, again locking itself under load from pinion gear. After more than 5 rebuilds in different configurations of old and new gears, shims etc I found a gear-shims combo that works. From front to back: 2shims- new gear- old planetary gears with one shim - new gear - 2 shims. Its weird because factory new gears with double shims in front and back did not work ( everything was too tight), factory new gears with only one shim at each end also did not work locking itself

 

[Marc]

For diff i orderet set of new gears but it did not work, again locking itself under load from pinion gear. After more than 5 rebuilds in different configurations of old and new gears, shims etc I found a gear-shims combo that works. From front to back: 2shims- new gear- old planetary gears with one shim - new gear - 2 shims. Its weird because factory new gears with double shims in front and back did not work ( everything was too tight), factory new gears with only one shim at each end also did not work locking itself

Same story on my Radix 6 with red alloy center diff case.
Adding a second shim on each side like you did is the only thing that helped.
I noticed wear on the case itself, behind planetary gear. But adding 4 shims there didn't work.
I still have problems on the center area, that may be related to your other issue, but Radix is quite different...

Edit: Center diff is still failling.

 

[Marc]

Perhaps 100k oil is too much? I was on 50k before.
I bought my radix new 4 months ago.
Since then, I have done about 20 runs on 4S pack, mainly on road.

 

[Marc]

Hello, I bought used dementor as a roller, put my own electronics, almost everything works fine, car is a beast but i have 2 problems with center diffrential. Center diff have metal 7075 case, new cups and bearings, gears and spur gear are in good condition.
Firstly diffrential locks itself under load. After rebuilding everything seems to work fine, 0 grinding, smooth but as soon as load from drivetrain is applyed something inside is causing it to jam. So i tested it in my hands bit more and i noticed that when i twist diff holdnig by cups everything is ok on both direction, but when im holding by spur gear and try to twist by cup something is jamming. And that jamming is not like bit of grinding but like sudden lock after while without any prior signs. Internal gears looks fine, no wear on teeth, no shards etc.

Second problem is Centre Diff Bulkhead flex at load, part nummber C-00180-018. This hole for bearing in the middle seems to be larger than it should and bearing have to much space there no matter how tight i screw down 2 pieces. As a result when load from pinion gear is applied entire diff goes 2-3mm up in this place but stays in place at the other side where its mounted to motor mount. Then spur gear is rotating unevenly causing damage on itself and pinion gear. At first i thought that plastic bulkhead is old and give to much flex, bought new one and problem is exacly the same.

What is the answer to this problems? Buying set of diff gears, buying metal diff bulkhead? Diff gears are few euros but metal bulkhead is like 35 euro and could have same problems with hole for bearings to la

Hello, I bought used dementor as a roller, put my own electronics, almost everything works fine, car is a beast but i have 2 problems with center diffrential. Center diff have metal 7075 case, new cups and bearings, gears and spur gear are in good condition.
Firstly diffrential locks itself under load. After rebuilding everything seems to work fine, 0 grinding, smooth but as soon as load from drivetrain is applyed something inside is causing it to jam. So i tested it in my hands bit more and i noticed that when i twist diff holdnig by cups everything is ok on both direction, but when im holding by spur gear and try to twist by cup something is jamming. And that jamming is not like bit of grinding but like sudden lock after while without any prior signs. Internal gears looks fine, no wear on teeth, no shards etc.

I did find out why grinding is only when holding spur gear : That's wear inside diff case!
Precisely, around planetary axle (pin?).
When in normal use (no differential), this 4 area are under constant load and get uneven wear, that generate grinding noise and locks.
I would change diff case and axle too.

 

[Kromeczek]

I did find out why grinding is only when holding spur gear : That's wear inside diff case!
Precisely, around planetary axle (pin?).
When in normal use (no differential), this 4 area are under constant load and get uneven wear, that generate grinding noise and locks.
I would change diff case and axle too.

yeah, it's weird,
in case of pins i thought about that too. for me old planetary gears rotate on pins smoothlyn new ones are bit too tight , did not see any wear on pins, front and back gears pins also looks fine, 0 play.
the housing does not look damaged in any way, its really well-machined piece of metal. Also any type of oil which I poured there has no effect on blocking. Im running configuration of gears witch i mentioned above for more than a month, zero problems, center diff is working nicely, metal diff case is really good heat conductor. I willl write another post after opening diff. For now everything is working fine, no locking issues.

For my taste issue was in gears, diff case tolerances form factory, something was not right with dimensions and gears ware locking itself. Anyway problem is fixed for me at least for now.