Torque Settings

[ScottR400D]

Another common question but does anyone have a definitive figure for torquing the bolts connecting the prop to the BMW diff?

My 2015 manual says 74Nm, the new manual says 47Nm. Presumably one’s a misprint but which?

I also read blogs that say ‘60Nm according to manual’. 

Also anyone know the settings for the diff to its holding bracket? In my 2015 manual it gives some figures but they refer to the older bracket, not the later one that I have. 

[Jonathan Kay]

Please check your Private Messages from yesterday.

[Geoff Brown]

Prop shaft connection - It will be difficult to get a torque wrench in there even with a multiplier extension & preventing the shaft from movement at the same time.

Thread lock & tighten to two grunts & a skinned knuckle.

[Garry7]

Hi Scott,

My build manual (Assembly Guide) from late 2011 early 2012 states:

13. Attach the propshaft to the differential output flange using the 4 caphead bolts (polythene bag 'miscellaneous'). No washers are required. Tighten to 74Nm.

However, I was sent the Workshop notice by Sean (the old Derek) during the build.

Caterham workshop notice number 530 dated 10/2/11/states the following:

12. Attach the propshaft to the differential pinnion drive flange with 4 off M10x20 supplied in the Z - pack and torque to 60Nm.

Best

Garry 

[ScottR400D]

Thanks guys. I haven’t had an issue getting in there with my smaller torque wrench. I put the car back together today and torqued them to about 50Nm, with the car in 1st gear. (No brakes on the rear at that point)

What I’ve gathered so far, Garry, is that before 2015 it was 74. In 2015 it changed to 60Nm but was left at 74 in the final check table. The latest diagrammatic manual says 47.

I’m going to redo tomorrow to 60. In truth, as Geoff implies, it’s probably not critical but I always like to have some logic in the process and these varying numbers make no sense. 

Looking on line at various manufacturer guides a 12.9 M10 is rated at 70 to 95Nm, depending on the site so 60 will be fine for the bolts and I’m pretty sure the flange is good for that. 

[DJ.]

If you re-torque the bolts now, it may disturb the thread lock which will have set in the meantime.

If you plan to adjust the torque, I would undo them, re-apply lock tight and then torque them up to the new figure. I always apply paint to mark the flange and bolt head, so I can visually check for movement while under the car without re-torquing each year.

Duncan

[ScottR400D]

Thanks Duncan. Yes that’s what I’ll do. Remove each one in turn, clean, new loctite, refit. 

I have paint marks on must of the nuts and bolts, it does speed up a check. 

[aerobod - near CYYC]

One issue I've had in the past is loss of the M12 allen lower mounting bolts between diff and diff carrier (I have lost 2 bolts at separate times and had one loosen), even with the Schnorr washers and blue loctite. The torque is only quoted at 60Nm in the 2012 assembly guide in one place and 81Nm in another, but I have upped mine to 100Nm (no problem for a 10.9 M12 bolt, but the diff casting could be the limiting factor). No further bolt loss or loosening now for about 3 years.

[ScottR400D]

That’s interesting James. They have been out for the rebuild and were put back in with 243 Loctite Blue at 81, the recommended figure. 

They've never been a problem for me but this the first time they’ve been disturbed since the car was built and the kit came with the diff assembled to the carrier. 

I’ll keep an eye on them. 

[aerobod - near CYYC]

It may depend on how the car is used, mine has had a fair number of track days and auto-x events using slicks. Although I always do a spanner check on the car before events, the bolts may have loosened during them; I lost the bolts on the road between events, then noticed a clunking from either a missing or loose bolt.

[ScottR400D]

Mine’s mainly on the road with a couple of TDs each year.