242 transfer case maximum torque

[Jeepinpete]

Just want to run some figures pass you guys, I'm going to fit a 242 transfer case to my diesel XJ instead of the 231 to get fulltime 4 wheel drive. Seemed like a good idea!
Checking out some torque figures I reckon my XJ put's out 300Nm max at 2000 rpm. So assuming worst case that's 1st gear (3.75:1) TC lo ratio (2:1) Max torque will therefore be 300 x 3.75 x 2 = 2250Nm.
Max torque of a normal 242 case is specified at 2015Nm. So I'm exceeding max torque by 200Nm.
So cut to the chase Is this really going to be an issue? there is going to be a safety margin surely and I very rarely use 1st gear 2000 rpm drop the clutch in lo ratio!! so am I ever likely to reach this sort of torque.
I could upgrade it to the 242HD but that is not an option at the moment. For info the 4.0l and the AW4 autobox is only 1647Nm so is well inside spec and the 231 is specd at 2556Nm which is why only the 231 was fitted to manual gearboxes and diesels.

So opinions please Am I going break it!

Cheers
Pete

 

[creeperjeep]

Dude, Imperial?
IT will prolly break at some point, J.ust E.xpect E.very P.roblem
Diesel,,, you mean a renault or you have a swap-in from like a yota?

 

[Jeepinpete]

Nm lb/Ft it's all relative!! 300Nm is 220 ft/Lbs roughly
The diesel is DCs VM 2.5TD as is available in europe and fitted to my XJ.

 

[Root Moose]

Nm lb/Ft it's all relative!! 300Nm is 220 ft/Lbs roughly
The diesel is DCs VM 2.5TD as is available in europe and fitted to my XJ.

Given it's only 200 N.m or so, go for the 242. How often will the t-case really see that? Very rarely, if ever.

Generally, automatics are gentler on the downstream mechanicals than a stick. That's the "joy" of a TC.

_IF_ you run into problems then you can start experimenting with the external coolers and such fitted to the 242 as seen in Dodge Durangos and Hummer H1s.

FWIW, I'm going to run a 242 behind a Chev 5.0 liter V-8 (~260 lb-ft) and a 700R4 transmission (3.06:1 first). We may be able to commiserate on how bad an idea it was in the future. LOL

HTH

r@m

 

[motorcityxj]

this link gives the max torque capacity of the different NV tc's.

http://www.newventuregear.com/tcases.html

 

[old_man]

Nice link. Got to save that one.

 

[woody]

Just an observation that the low range ratio in the US spec 231 and 242 are 2.72:1. Are the UK spec 2:1 reduction? If not, that twists things up to 3060Nm or thereabouts...

At the same time... I wouldn't hesitate to put a healthy 242 behind either a diesel or gas motor with a manual transmission... Assuming it's not driven like a WRC car, it should do fine.

 

[Jeepinpete]

Your right, my error the transfercase is 2.72:1, but I have a feeling from doing it a bit more searching that the torque capacity quoted at the new venture gear website is for lo range already in which case the 2.72:1 comes out the equation and we are both ok.
I was hoping somone may confirm it!

Pete

 

[MarcoXJ]

You can find many Diesel XJs in Europe and there are also a few guys who did this swap and it works great.

 

[Root Moose]

For the purpose of this discussion the transfer case ratio is irrelevant, no? We are talking transfer case input torque, that is, upstream of the transfer case.

I took the original poster's TC to mean the torque converter and the normal rule of thumb for that is to apply a 2:1 ratio to that to model the action of the torque converter. IIRC, the civilian Hummer H1 brochure uses 2.2:1 for the torque converter in gearing calculations. That would be for the 700R4/4L60 transmission.

So, his numbers are valid even if that is not what he intended. LOL

r@m