I'm wondering how well a 28 spline 9 inch pinion holds up. Is the 35 spline pinion a necessary upgrade in a buggy with a very healthy V8, 5.14 gears, and 38" tires, weighing about 3000 lbs? Just looking for someone out there who has experience with this. Thanks.
Ford 9 Inch Pinion Spline
- Thread starter CSR
- Start date
X1994J
XJ's Bring the Uni-Suck
- Location
- Herriman, UT
I don't know a lot about the 35 spline and aftermarket stuff for the 9", but I have been running a big bearing 31 spline shaft 9" under my rig for the past Year and a half. I have a pretty heavy foot and it has held up great, my Jeep weighs about 4200 lbs on 37" tires, although I am running a little 4.0L engine. A coupe trips ago I had the case come apart on me, other than that it's been stout. Are you running a Nodular / upgraded case? I think with it only weighing 3000 lbs. you'd be fine, i'd be more worried about the case than the Pinion spline count. 
Raleigh
OMF Dave
- Location
- VIVA LAS VEGAS
This is my thought as well, but @ 3000# you may not have to worry much on that either!i'd be more worried about the case than the Pinion spline count.
TEAM FRED
Registered User
- Location
- Centerville
35 spline pinnion not needed. Nodular housing should be required.
X1994J
XJ's Bring the Uni-Suck
- Location
- Herriman, UT
RockChucker
Well-Known Member
- Location
- Highland
Chris, I don't know much about how the spline count on the pinion will be a factor. I'm sure there is some there, but correct me if I'm wrong, a pinion with 5.13's has less stress on it than a pinion with say 3.55's? Another thing to think about is which brand of gears you run. Get some good ones that aren't going to blow up on you. This might be a good thing to talk to Casey about.
-Dave
-Dave
RockChucker
Well-Known Member
- Location
- Highland
Chris, I don't know much about how the spline count on the pinion will be a factor. I'm sure there is some there, but correct me if I'm wrong, a pinion with 5.13's has less stress on it than a pinion with say 3.55's? Another thing to think about is which brand of gears you run. Get some good ones that aren't going to blow up on you. This might be a good thing to talk to Casey about.
-Dave
-Dave
UNSTUCK
But stuck more often.
A 5.13 pinion gear would have more stress on it vs. a 3.55 gear due to their size. A 3.55 gear is huge compared to a 5.13. The bigger gear has bigger teeth witch will spread the load to a bigger area decreasing the chance to a chipped or broken tooth. There is also the added torque multiplication of the 5.13 which would increase the load placed on these parts.
CJ Matt
Registered User
Yes... once we tore it apart the pinion guard was tweaked as well which probably helped contribute. It also broke a chunk out around the pinion bearing. But this as been known to happen before to others.
Looks a lot like what happened to mine.
RockChucker
Well-Known Member
- Location
- Highland
unstuck-
right. i understand the pinion itself is stronger with a higher gear ratio. but there is less stress on the pinion shaft itself, right? my logic follows this, it is a heck of a lot harder to break an axle in 4 hi than in 4 low. the torque is multiplied through each reduction, so in low range, the tranny feels less stress than high range and on down the line...or does a pinion feel the same torque no matter what?
right. i understand the pinion itself is stronger with a higher gear ratio. but there is less stress on the pinion shaft itself, right? my logic follows this, it is a heck of a lot harder to break an axle in 4 hi than in 4 low. the torque is multiplied through each reduction, so in low range, the tranny feels less stress than high range and on down the line...or does a pinion feel the same torque no matter what?
UNSTUCK
But stuck more often.
We may be getting off topic here, but here goes:
Say your engine produces 10 lbs/ft of torque at 1000 rpms. First gear in your tranny is 2:1. So now you have 20 lbs of torque, but are moving at half speed. Your tcase is also 2:1 in low range, but 1:1 in high. So in low range you are putting out 40 lbs of torque, but have cut your speed in half again.
So crawling up Waynes world in low range at 1000 rpms will put 40 lbs of torque on your pinion shaft. Do that same thing in high range your pinion shaft would see only 20 lbs of torque, but make that climb twice as fast.
Your pinion shaft has a fail point of x lbs of torque. No matter what range you are in, climbing Waynes World or mall crawling, once that number is reached, the shaft will break.
I have no numbers about breakage in hi or low range, and it doesn't matter. All this gearing does is effect the engine ability to make power. So when it seams like there is less stress in low range, that is just because the lower gears are making it easier for the engine to remain running. So to do the same thing in high range would require a heavier foot or slipping the clutch, both would produce more torque, which would see its way to the pinion shaft. So a 35 spline shaft, which can handle more torque, will last longer.
Anyways, going back to the op, from the pictures I don't see pinion failure. Just a weakish case.
There will be a test this Friday on the effects of torque multiplication on pinion shafts.
Say your engine produces 10 lbs/ft of torque at 1000 rpms. First gear in your tranny is 2:1. So now you have 20 lbs of torque, but are moving at half speed. Your tcase is also 2:1 in low range, but 1:1 in high. So in low range you are putting out 40 lbs of torque, but have cut your speed in half again.
So crawling up Waynes world in low range at 1000 rpms will put 40 lbs of torque on your pinion shaft. Do that same thing in high range your pinion shaft would see only 20 lbs of torque, but make that climb twice as fast.
Your pinion shaft has a fail point of x lbs of torque. No matter what range you are in, climbing Waynes World or mall crawling, once that number is reached, the shaft will break.
I have no numbers about breakage in hi or low range, and it doesn't matter. All this gearing does is effect the engine ability to make power. So when it seams like there is less stress in low range, that is just because the lower gears are making it easier for the engine to remain running. So to do the same thing in high range would require a heavier foot or slipping the clutch, both would produce more torque, which would see its way to the pinion shaft. So a 35 spline shaft, which can handle more torque, will last longer.
Anyways, going back to the op, from the pictures I don't see pinion failure. Just a weakish case.
There will be a test this Friday on the effects of torque multiplication on pinion shafts.
We may be getting off topic here, but here goes:
Say your engine produces 10 lbs/ft of torque at 1000 rpms. First gear in your tranny is 2:1. So now you have 20 lbs of torque, but are moving at half speed. Your tcase is also 2:1 in low range, but 1:1 in high. So in low range you are putting out 40 lbs of torque, but have cut your speed in half again.
So crawling up Waynes world in low range at 1000 rpms will put 40 lbs of torque on your pinion shaft. Do that same thing in high range your pinion shaft would see only 20 lbs of torque, but make that climb twice as fast.
Your pinion shaft has a fail point of x lbs of torque. No matter what range you are in, climbing Waynes World or mall crawling, once that number is reached, the shaft will break.
I have no numbers about breakage in hi or low range, and it doesn't matter. All this gearing does is effect the engine ability to make power. So when it seams like there is less stress in low range, that is just because the lower gears are making it easier for the engine to remain running. So to do the same thing in high range would require a heavier foot or slipping the clutch, both would produce more torque, which would see its way to the pinion shaft. So a 35 spline shaft, which can handle more torque, will last longer.
Anyways, going back to the op, from the pictures I don't see pinion failure. Just a weakish case.
There will be a test this Friday on the effects of torque multiplication on pinion shafts.
You need to go one step further--your 40 lbs of torque on the pinion shaft will be multiplied again by the axle gearing--so a deeper axle gear will put more torque through axle shafts. (and thus, with a given amount of torque on the wheels, reduce the stress on the pinion shaft compared to a taller axle gear)
RockChucker
Well-Known Member
- Location
- Highland
yep....i was totally thinking backwards. thanks for straightening me out