241 vs 241HD

[rspinks]

Could somebody please explain the differences between the “standard” 241 t-case and the “HD” version? What do I have in my ETH/DEE? I don’t have the snowplow prep package, just camper/trailer options. I couldn’t see any “241” or “241HD” casting on the case itself.



What are the internal differences? Should I be concerned if I have the weaker case in my truck? What failures have been associated with these transfer cases?



Thanks,



RS

 

[DEZLPWR]

I also would like to know this....

I do not have the HD transfer case and was wondering if/how long it could handle the HP I'm putting out.

 

[Thomas]

DHG inside glovebox door = 241HD



Transfer Case Specs (thanks Dave Fritz).

 

[Rob Thomas]

If your tranfercase has a pto cover it's a 241HD, if not it's a 241.

 

[rspinks]

Sounds like 241D then

Thanks for the link to Fritz' page, wealth of info like usual.



Any failure reports on our transfer cases? What eventually gives and under what conditions? I know some people drag race these trucks in 4WD - I don't imagine they are all running 241HD's so the basic case must be pretty stout. Of course you could probably break it by abusing a standard trans. in the lower gears.



I'll have to check in the glove box for the mystery tag - couldn't find any tags on door jambs or rad. support like my '94 had.



RS

 

[Rob Thomas]

A freind of mine's broke once,we took it apart and found the ends of the shift fork wore through,then caused it to engage and broke the chain and various other parts. He was on the expressway when it let loose.

 

[Joseph Donnelly]

The 241HD is rated for 1400 ft lb and the regular 241 is for 1000.

 

[ramcam6]

Anyone know what code DHH for a transfer case references?



Thanks, Charlie

 

[rspinks]

I have DHH also and no PTO cover so I guess this is the standard diesel tcase (ie: not the HD).



I've been frightening myself today with the following thought: Tcase rating 1000ftlb continuous input torque. Hmmm, 505ftlb @ flywheel multiply by 5. 61 first gear = 2800ftlb @ transfer case!Maybe I should cease my full throttle 3rd gear 4wd powersliding around town on snow!



RS

 

[C.]

My truck has the NV241LD. On the back of the transfer case there is an I. D. tag. It has some red paint on it and it is round. I had to wipe it off good to read the info.



I replaced the rear extension seal on mine (leaking). Only problem I have had with the transfer case.



I just dropped the truck off at the dealer. BRAKE and ABS warning lights are on.

 

[DavidD]

I beleive but dont qoute me but the 241HD has a chain drive as well and the 241 is gear drive. Also I know the HD is shift on the fly. Dave

 

[HillCountrykid]

All of the NVG transfer cases for light duty trucks are chain driven.



Brian

 

[apkole]

I've heard of one instance of a case coming apart at highway speeds, doing a great simulation of a grenade. The drivetrain people I've spoken to indicate that most failures start with a leaking input or output shaft seal. Inattention of the owner results in driving with low fluid levels, which then contributes to the failure of the t'case components.



I park on cement most of the time and make it a habit to do a coursory check for dark spots under the truck before entering the cab. During the winter months the red fluid shows up readily on white snow.



A more frequent cause for repair in our industry is when a driveshaft u-joint fails, allowing the shaft to flop around under the truck and cause all kinds of death and distruction to the transfer and transmission housing. Again, there is no replacement for routine inspection and maintenance.



Andy

 

[Mathew Clausen]

rspinks - although in theory your mighty cummins could put out 2800 ft*lb at the back of the trans in 1st - you will never get there in the vehicle because it will spin out first.



Some quick calcs with 3. 54 rear ends, trans in high range, and 30" tires gives the following relation:



Force to tires (lb) = Transfer case input torque (ft-lb) * 2. 83



Assuming a coefficient of friction of 0. 7 for dry pavement and that your rig weighs 7000 lb - the max force your tires could see on dry pavement would be 4900 lb.



So - the max transfer case torque would be 1731 ft-lb before spinning out in 4wd on dry pavement. Change to 2wd (less than half the weight on driving tires) or snow (less coefficient of friction) and the max torque would drop significantly.



Mathew

 

[klenger]

So, are you saying you could get by with a lighter transfer case in a 2WD?

 

[rspinks]

Mathew,



Thanks, I follow your theory. What is happening at full thottle acceleration on dry pavement in 3rd gear? Assuming I am getting full boost I should be making 505ftlb and the tires aren't spinning. Guessing 2. 5 as 3rd gear ratio wouldn't I still be putting 1262ftlb into the transfer case, ie: over the continuous rating?



Rich

 

[CAM]

My vehicle option sheet says : DHHS transfer case/shift-on-the-fly 241

 

[Mathew Clausen]

For your curiosity - ratios as follow:

1st 5. 63

2nd 3. 38

3rd 2. 04

4th 1. 39

5th 1. 0

6th 0. 73

Rev 5. 63



So even with 2. 04 I guess you are correct at being over the max recommended continuous. Is there heavy enough trailers out there to keep the keep the engine pulled down in 3rd?



One other thought I had - I suspect that the max input rating for the t-case is limited when you are in Low range (more forces on output shafts). Put another way - if it will handle 1000 ft-lb in low which multiplies by another 2. 7 - high range should never be a problem.



I think you probably can't hurt the t-case in a "continuous" type load - what possibly can is spinning full rpm and then hooking up to say pavement - lots of inertia in the engine and clutch to pull down. The good thing for your transfer case is there is this max torque limiting device called a driveshaft that will probably break first .

 

[apkole]

K. Lenger,



Soooo, would that be a question for Papa Bull or Mama Bull?



Andy