pugwash Posted August 13, 2006 Share Posted August 13, 2006 So a portal axle will sginificantly reduce the stress across the axle when accelerating, but, if you are going down a hill and using engine breaking, is the portal axle multiplying torque "up" the drivetrain. e.g. You are descending a hill and need 300 ft/lb to maintain your current speed. A normal axle is revolving the propshaft at 30 rpm. Now a portal will have dropped that gearing, so 300 ft/lb will be pushing an a prop shaft at say 20 rpm. Now by my calculations that means the lower turning prop shaft will be under more torque. For an auto box this would be a bad thing yes? so what i have got wrong with this thinking? or am i right- and in reality it's not a problem? Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted August 13, 2006 Share Posted August 13, 2006 So a portal axle will sginificantly reduce the stress across the axle when accelerating, it's not a problem? Erm Not with a diesel vs a nice V8 Sorry, couldn't resist I'm going.............................. Nige Quote Link to comment Share on other sites More sharing options...
dollythelw Posted August 13, 2006 Share Posted August 13, 2006 prop shaft spins faster with a portal than a non-portal, as the ratio is higher, the higher ratio will give greater control down hills as your engines torque is multiplied, if you had a weedy v8 you would need 400+ ft/lbs of torque to equal a portal'd diesel coat on........ chugging off sedately leaving a plume of cheap-to-run, nutritous black smoke thanks for the biccies Nige Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted August 13, 2006 Share Posted August 13, 2006 Nige Quote Link to comment Share on other sites More sharing options...
dirtydiesel Posted August 14, 2006 Share Posted August 14, 2006 The prop will be turning at roughly twice the speed but it will have half the load to deal with. Any back loads that make it through the portal gears, diff gearing and transfer gearing is unlikely to do any damage. Because of the (roughly) 2:1 gearing of the portal boxes, your entire driveline "behind" them is equivalent to twice the strength. Quote Link to comment Share on other sites More sharing options...
pugwash Posted August 14, 2006 Author Share Posted August 14, 2006 , if you had a weedy v8 you would need 400+ ft/lbs of torque to equal a portal'd diesel 400 lb/ft is no problem for those of us with a properly built V8 Coat on Accelerating out of the door leaving the stinky Diseasels behind The prop will be turning at roughly twice the speed but it will have half the load to deal with. DOH knew i'd have got it wrong somewhere- i was working out the gearing the wrong way round. Idiot Quote Link to comment Share on other sites More sharing options...
dollythelw Posted August 14, 2006 Share Posted August 14, 2006 you're gonna have to find 635ft/lbs to out tug petal next season oh the joy of 24mpg............. tum de dum ooooo wheres that puddle? a spark what? oh plug yes I remember those... (mmm black planet warming lovelyness) Quote Link to comment Share on other sites More sharing options...
bill van snorkle Posted August 14, 2006 Share Posted August 14, 2006 So a portal axle will sginificantly reduce the stress across the axle when accelerating, but, if you are going down a hill and using engine breaking, is the portal axle multiplying torque "up" the drivetrain. e.g. You are descending a hill and need 300 ft/lb to maintain your current speed. A normal axle is revolving the propshaft at 30 rpm. Now a portal will have dropped that gearing, so 300 ft/lb will be pushing an a prop shaft at say 20 rpm. Now by my calculations that means the lower turning prop shaft will be under more torque. For an auto box this would be a bad thing yes? so what i have got wrong with this thinking? or am i right- and in reality it's not a problem? I am too Portalled and 3 linked out to respond to this thread. Bill. Quote Link to comment Share on other sites More sharing options...
pugwash Posted August 14, 2006 Author Share Posted August 14, 2006 you're gonna have to find 635ft/lbs to out tug petal next seasonoh the joy of 24mpg............. tum de dum ooooo wheres that puddle? a spark what? oh plug yes I remember those... (mmm black planet warming lovelyness) Right that's it i warned you. i have just been offered a written off 5.0 V10 TDi from a Toureag. Recokn after a bit of fettling it'll eat you for breakfast. pah- i fart on your 635 puny pieces of torque. I reckon this bad boy'll do 1000! would have to get a seriously funky drivetrain to match though. on second thoughts i'll stick with my Rv8 which makes a proper noise (next upgrade would be a stroked LSx anyway- 6.3L of pure ali american muscle- hmmmmmmmmmmm). My last 4.0 V8 would quite happily do 21mpg when all kitted up- so don't think you're saving too much! Quote Link to comment Share on other sites More sharing options...
dollythelw Posted August 14, 2006 Share Posted August 14, 2006 I'll save the last 3mpg for towing you to the petrol station its all good the key though is get the projects finished! Quote Link to comment Share on other sites More sharing options...
pugwash Posted August 14, 2006 Author Share Posted August 14, 2006 its all good the key though is get the projects finished! Not for me- getting them started is hard enough :D let alone getting them finished! Quote Link to comment Share on other sites More sharing options...
jules Posted August 14, 2006 Share Posted August 14, 2006 My last 4.0 V8 would quite happily do 21mpg when all kitted up- so don't think you're saving too much! The challenge truck I would measure fuel over time as it was not worth looking at the mpg. 1 x tank of fuel = 5 hrs playing or competing The greenies love me Quote Link to comment Share on other sites More sharing options...
GBMUD Posted August 14, 2006 Share Posted August 14, 2006 The challenge truck I would measure fuel over time as it was not worth looking at the mpg. 1 x tank of fuel = 5 hrs playing or competing The greenies love me I am not sure that TDi engines use fuel off road. Do they? Chris Quote Link to comment Share on other sites More sharing options...
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