Thread: Detroit rear locker

Originally Posted by Naks

chaps, I fitted an ATB in the rear of my Puma in October 2017, and recently started noticing a groaning noise that's becoming quite bad.


My indie and I eventually traced it to the rear diff: at specific rpm/speed, there is a loud, low-frequency groaning noise + vibration emanating from the rear of the car. It almost feels as if the seats have built-in massage function, especially when I hit 80-100kmh.


Has anyone else experienced this after fitting an Ashcroft, and if so, how did you fix this?


thanks

Two things to suggest...
Number 1:
- This is unlikely to be anything to do with the ATB internals, as the helical gear sets do not rotate on their own axis at high speeds. With the vehicle moving in a straight line they would barely rotate at all inside their pockets. (Both the pockets and the helical gears, the whole diff centre, would be rotating on the same axis as the crownwheel, but no real movement of the helical gears relative to their pockets)

Number 2:
- I bought two Ashcroft ATB's for front/rear of my 2013 TDCi (Puma) 110 a couple of years ago. Bought two recon diffs from Ashcroft at the same time, and had Ashcrofts assemble with the new ATBs with all new bearings etc for me as I didn't trust anyone locally (Malaysia) to do the job.

- from new I had some noises similar to what you mentioned, getting worse after several hundred km

- on checking (pulled the diff) found that there was a fair bit of runout measured at the crown wheel

- seems on some diffs there is a possibility of interference between the crownwheel and ATB. Had to chamfer off a bit...

- solved the issues. Ashcrofts came to the party covering my costs to rectify (since they had assembled the diff/ATB originally)

Thanks Neil, the crownwheel runout seems to be the culprit

edit:

Just spoke to my indie and he says all the adjustments were done during the fitment... so he's going to take it out and inspect it.

Originally Posted by Naks

Thanks Neil, the crownwheel runout seems to be the culprit

edit:

Just spoke to my indie and he says all the adjustments were done during the fitment... so he's going to take it out and inspect it.

Not sure what adjustment is being referenced. No amount of setting up of the crown wheel to pinion engagement will sort the issue I had.

The issue I had was around the crown wheel not sitting completely flat against where it mates, bolts up, to the diff centre/ATB. Kinda put a measurable warp in it (crown wheel), seen via dial gauge.

Originally Posted by Naks

Thanks Neil, the crownwheel runout seems to be the culprit

edit:

Just spoke to my indie and he says all the adjustments were done during the fitment... so he's going to take it out and inspect it.

Any runout should should be detected when setting backlash .You need a better mec

AM

I Had to buy a spacer ring for the rear diff centre when I fitted ATB's into my 2012 130.

Without the spacer I don't think it would have fitted.

Whoever assembled the diff should have been checking that everything was bolted tight and that no runout was occurring.

Ian
Bittern

Originally Posted by ian4002000

I Had to buy a spacer ring for the rear diff centre when I fitted ATB's into my 2012 130.

Without the spacer I don't think it would have fitted.

Whoever assembled the diff should have been checking that everything was bolted tight and that no runout was occurring.

Ian
Bittern

That would be because yours runs a p38 rear diff. Normally not needed

I had a Detroit in the rear of our D1 and it was excellent. Don't put one in the front as it affects steering. You need a Tru Trac in the front.

Tru Trac TBD are available as either front or rear.I have been running a rear in the front for nearly 4 years and it has been perfect with no adverse effects.It is a simple job to reconfigure the gears but can't imagine it being any better so won't bother

AM