Low Gears

[blacksheep10]

I'll always argue for deeper diff gears up to the point they become weak. We didn't have great luck with 6.17's, but part of that is LP in front, and the rears that blew up had other circumstances involved. I think I still have 3 dana 70's out back with 6.17 or 7.17 from ditch witches. Not sure if they're still free or surface rusted. Was always going to do something and didn't

 

[tallnate]

the tooth count is not as big of a deal At any given point you only have"x" amount of contact A 9 nine 6.20 pinion is like 6 tooth but the teeth are fat compared to a higher count pinion i have smashed my 400 plus HP moonbuggy into backdoor smoking sticky trep 42s full of water with Dana Spicer 6:17s ive shattered spidertrax units {old ones} 300M rcv 35 spline inners but no R&Ps

I guess my point is for example.. all things being equal a dana 60 3.73 with a much larger 11 tooth pinion is going to handle more stress load events than smaller pinion dana 60 6.17 that has 5 less pinion teeth. Because with lower gear ratio's there's less teeth to do the work in comparison to higher gear ratios. So with less teeth to drive on, the load on those teeth is going to be greater which over time leads to quicker fatigue and breakage when compared to a higher ratio that shares the load over a larger area.

 

[nvrenuf]

Your comparison should be more realistic, like 5.13's instead of 3.73's. I can't imagine anyone that was considering a ballpark of 6.17's would value a comparison to 3.73's. That's like using 22R logic on a 350 for better mpg's.

Now, my 5.86's have 7 pinion teeth whereas 5.13's have 8, so there is a difference there but not like the next step to a 6.17 which has 6.

 

[tallnate]

Your comparison should be more realistic, like 5.13's instead of 3.73's. I can't imagine anyone that was considering a ballpark of 6.17's would value a comparison to 3.73's. That's like using 22R logic on a 350 for better mpg's.

Now, my 5.86's have 7 pinion teeth whereas 5.13's have 8, so there is a difference there but not like the next step to a 6.17 which has 6.

Well obviously.. It was just an example to explain the reasoning behind why a low gear ratio is physically not as strong as a higher gear ratio. The concept is the same across the spectrum of high to low. The lower the ratio the weaker it gets due to the lesser quantity of ring and pinion teeth to share the workload.

 

[nvrenuf]

I understand the concept is the same, my point was about getting people to listen to the whole concept instead of shutting down part way through.

 

[Trailabite]

I'm leaning towards the 5.38's, maybe 5.86.

 

[nvrenuf]

I'm leaning towards the 5.38's, maybe 5.86.

5.38's have 8 teeth like a 5.86, might as well go all the way.

 

[POR]

But as the gear ratio goes lower it gains more leverage to spin, which lowers the working stress on the pinion teeth. Most of the old SN Fab cars ran 6.17's and still do to this day. One of the guys in our group runs a pretty healthy motor on 6.17's and they've been holding up for years. Ive always felt heat more than anything killed the pinions. 5.13's and 5.38's are a very good all around working low gear. They still give ya ample wheel speed when needed. I'd run 5.13's if it were me lol