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pistonfields

Member Since: 29 Mar 2022
Location: Zurich
Posts: 72

LT230 front differential bearing preload

Hi all
I'm rebuilding my LT230 (Puma) and have troubles setting the front differential bearing preload. I had to set it as I have put in an ashcroft diff, have replaced all the bearings and got a case swap. I followed the manual and have used Nigel's method of measuring preload with shimming the case, measuring play and adding the power of math. yeah.

Having all the dials and tools at hand helped a lot! I aimed for the 0.05mm preload and might have been a tad over it (0.06mm, not sure tbh).
It took me way more tries to get it right than I would have guessed (mainly because my math skills aren't as good as they used to be... well no, they seem to be as bad as I remember them

).
The rear output housing with output shaft is now on with propper sealant (rear bearing race was pushed in correctly with the case torqued to spec whilst dry fitting and setting preload), and I have now the front case including the front output shaft on (dry), torqued to spec.

My problem: the assembly turns rather hard now. Way harder than when I was setting preload (without the front and rear output shafts in). I then used the string method to get an idea of how much force it would require and measured something around 4-4.8kg, but sometimes around 3kg. Readings aren't consistent which adds to the frustration.
Having found an old LT230 manual I got 1.36kg to 4.53kg for the string method, without the front and rear output shaft in. That's my reference for now.

My question: what's going on? Do the front and rear output shaft add that much drag? Or have I cocked up my preload in the first place? Do 0.01 (give or take a bit) really add that much preload? Having only 0.05mm shims makes it rather difficult to get it spot on, so I imagine there must be some margin (the rather wide range for the string method seems to confirm this).

(PS: I used ashcrofts shim kit. The shims seem to be lasercut out of sheet metal and have nasty burs. I thus debured them before installing them. Took me some tries to realize that this was adding to the problem of not being able to get consistent readings when initally measuring shim thickness whilst setting preload. The rest of their stuff, including his support, is top-notch though.

)

27th Apr 2022 7:43pm

blackwolf

Member Since: 03 Nov 2009
Location: South West England
Posts: 17442

2007 Defender 110 Puma 2.4 DCPU Stornoway Grey

If oil seals and flanges are fitted then the additional torque to turn the shafts will be significant.

27th Apr 2022 7:51pm

pistonfields

Member Since: 29 Mar 2022
Location: Zurich
Posts: 72

The flanges haven't been fittet yet, the oil seals are in. All the bearings got oiled. I measured it again for a couple of times and got something between 3.5 and 4kg with the China scale, which is within specs of that old manual, albeit being on the upper end.

27th Apr 2022 8:00pm

blackwolf

Member Since: 03 Nov 2009
Location: South West England
Posts: 17442

It sounds as though you don't have much to worry about, I wouldn't be too concerned.

27th Apr 2022 8:05pm

pistonfields

Member Since: 29 Mar 2022
Location: Zurich
Posts: 72

May I ask a related question: I have assembled the input shaft too and this time I feel the preload was waaaay to low. With the scale it only required 0.2kg of force to turn it (without intermediate gears). I initially set it using Nigels method with shims between the case. After disassembling and cleaning it I measured again: 0.03mm. So I'm doubting the dial / arm I'm using. Might be too unstable and giving me a too high margin of error.
That's why I went with the scale method next, again referencing the old manual that specifies between 2.26 to 9kg preload for the input shaft (a rather large margin). After adding shims and measuring again and again I'm currently at around 3.9kg force required to turn the input shaft (string wraped around the cross drilled part of the shaft). To me that feels rather tight, but then again I have no experience with the LT 230.

28th Apr 2022 10:14pm

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