high pinion????

Nuts · 08-14-2011, 07:47 PM

Always heard not to run a high pinion in the rear but is it really that much weaker? If the gears are designed to run that way how does it matter if its in front or out back?

94Dodge Truggy · 08-14-2011, 08:27 PM

I have heard that it is 20-30% weaker. If you are low HP and mild tire size it may survive.

carwash · 08-14-2011, 10:21 PM

Reverse cut gears are stronger in front application, but at least 20% weaker in the rear. There is a lot of tooth deflection on these due to the type of engagement they have. Most manufacturers suggest no more than a 35" tire and mild horsepower.

But i've seen guys run them and beat the snot out of them and have no issues at all.

blazerbrad · 08-15-2011, 11:21 PM

As mentioned above, a high pinion (or reverse rotation) gears were designed for the front so they were powered on the drive side of the gears = stronger. Put a high pinion in the rear and you are now running on the cost sides = not as strong. Same type of situation but reverse of a low pinion (standard rotation) gears......powered on the drive side when in the rear but cost side if in the front.

I periodically hear about people blowing out the R&P in high pinion rear 60's in rigs like TJ's with 38's, but this is all second hand and I'm sure only a small percentage. A guy in our club has one in his YJ with 37" Boggers with the 4.0L, NV4500, and 4-speed Atlas (manual combined with low gears = more stress). He's been beating on it pretty hard for a couple of years now, including a stint on a set of borrowed 42's, with no issues so far.

Nuts · 08-16-2011, 04:46 PM

I saw one yesterday that was blown apart so I think I'll go with plan B:mad:

flatlander757 · 08-16-2011, 08:44 PM

See how there is a flat side and an angled side of each tooth?

The flat side is the drive side, the angled side is the coast side.

High pinion in the rear = driving forwards on the coast side... so the pinion is basically pushing the ring gear away from itself about as hard as it is trying to turn forward.

If you want a high pinion rear it needs to be BEEFY to handle the abuse... I would consider a HP D70 as minimum... and even then I'd consider pinion bearing replacements as a normal maintenance item every few years.

Nuts · 08-17-2011, 10:14 AM

That makes sense, thanks.

T-bird · 08-17-2011, 10:40 AM

The same thing is true for a low pinion when you are driving in reverse ( you are pushing on the coast side of the gears). That is why you should not recover someone in reverse because it puts a lot of stress on the drivetrain and they are getting pushed away from each other.

flatlander757 · 08-17-2011, 11:24 PM

Quote:

Originally Posted by T-bird

The same thing is true for a low pinion when you are driving in reverse ( you are pushing on the coast side of the gears). That is why you should not recover someone in reverse because it puts a lot of stress on the drivetrain and they are getting pushed away from each other.

Right.

At the same time though, if you have a low pinion front then you're at least driving on the drive side if you do something dumb is reverse... but I would still never pull anyone out because stuff breaking up front is about 2x more expensive

kirbyiv · 08-18-2011, 10:51 PM

not sure why everyone calls it "reverse rotation"...the gears rotate the exact same way as a standard gearset.

There are "standard cut" gears and "reverse cut" gears. The difference being the direction the teeth are cut onto the gears so they mesh together since one is low pinion and one is high pinion

08-14-2011, 07:47 PM	#1
Nuts Join Date: Feb 2008 Location: middletown,oh Posts: 508	high pinion???? Always heard not to run a high pinion in the rear but is it really that much weaker? If the gears are designed to run that way how does it matter if its in front or out back?

08-14-2011, 08:27 PM	#2
94Dodge Truggy EX-Vice President Join Date: Jan 2007 Location: Fairfield, Ohio Posts: 3,048	I have heard that it is 20-30% weaker. If you are low HP and mild tire size it may survive. __________________

08-14-2011, 10:21 PM	#3
carwash pimpin' IS easy Join Date: Jan 2007 Location: Union, KY Posts: 3,344 Images: 605	Reverse cut gears are stronger in front application, but at least 20% weaker in the rear. There is a lot of tooth deflection on these due to the type of engagement they have. Most manufacturers suggest no more than a 35" tire and mild horsepower. But i've seen guys run them and beat the snot out of them and have no issues at all. __________________

08-15-2011, 11:21 PM	#4
blazerbrad - CORE Member - Join Date: Feb 2007 Posts: 831 Images: 6	As mentioned above, a high pinion (or reverse rotation) gears were designed for the front so they were powered on the drive side of the gears = stronger. Put a high pinion in the rear and you are now running on the cost sides = not as strong. Same type of situation but reverse of a low pinion (standard rotation) gears......powered on the drive side when in the rear but cost side if in the front. I periodically hear about people blowing out the R&P in high pinion rear 60's in rigs like TJ's with 38's, but this is all second hand and I'm sure only a small percentage. A guy in our club has one in his YJ with 37" Boggers with the 4.0L, NV4500, and 4-speed Atlas (manual combined with low gears = more stress). He's been beating on it pretty hard for a couple of years now, including a stint on a set of borrowed 42's, with no issues so far.

08-16-2011, 04:46 PM	#5
Nuts Join Date: Feb 2008 Location: middletown,oh Posts: 508	I saw one yesterday that was blown apart so I think I'll go with plan B:mad:

08-16-2011, 08:44 PM	#6
flatlander757 Fartface extrordinair Join Date: Aug 2010 Location: West Carrollton Posts: 127	See how there is a flat side and an angled side of each tooth? The flat side is the drive side, the angled side is the coast side. High pinion in the rear = driving forwards on the coast side... so the pinion is basically pushing the ring gear away from itself about as hard as it is trying to turn forward. If you want a high pinion rear it needs to be BEEFY to handle the abuse... I would consider a HP D70 as minimum... and even then I'd consider pinion bearing replacements as a normal maintenance item every few years.

08-17-2011, 10:14 AM	#7
Nuts Join Date: Feb 2008 Location: middletown,oh Posts: 508	That makes sense, thanks.

08-17-2011, 10:40 AM	#8
T-bird Join Date: Sep 2010 Location: Centerville Posts: 123	The same thing is true for a low pinion when you are driving in reverse ( you are pushing on the coast side of the gears). That is why you should not recover someone in reverse because it puts a lot of stress on the drivetrain and they are getting pushed away from each other.

08-18-2011, 10:51 PM	#10
kirbyiv Join Date: Apr 2009 Location: Cincinnati Posts: 27	not sure why everyone calls it "reverse rotation"...the gears rotate the exact same way as a standard gearset. There are "standard cut" gears and "reverse cut" gears. The difference being the direction the teeth are cut onto the gears so they mesh together since one is low pinion and one is high pinion