Low range 4,7 gear questions (1 Viewer)

[Dewil]

Hi!
Im entertaining the idea of swapping my standard 2.88:1 gears in my transfercase to lower range 4,7:1 gears. When doing the math it seems like the original low range overlaps 1st gear high when in 3:d gear low.
If changing to 4,7 gears all low range gears are below 1st gear high (except for 5th gear low which is he same as 1st gear high). Se the excel below sinse I realize its messy to explain.

Gear	1st	2nd	3rd	4th	5th
	3,954​	2,141​	1,384​	1​	0,85​
T-case Gear 2,88​	11,38752​	6,16608​	3,98592​	2,88​	2,448​
T-case Gear 4,7​	18,5838​	10,0627​	6,5048​	4,7​	3,995​

Is there any drawback to using 4.7 gears (except additional cost and labour) since it seems to produce more uniqe gear ratios? Is it somehow bad to put the transfercase in lowrange and start on 3rd,4th or 5th gear?
Input is appreciated!
//Will

 

[Heretic]

In my Toyota pickups (both stock XFer cases), I rarely use 3rd or 4th gear in 4Low, since it overlaps with 1stHi, and never 5thLo (unless it is a 6 speed - i.e., I believe that overdrive gearing is weaker than direct drive) - although it would be more convenient to be able to use 3rd & 4th if I was going to stay in 4Low - but then I don't do a lot of serious 4 wheeling.

Other than that, your table/chart does point out an additional benefit of the 4.7 reduction; i.e., a wider range of gear than the 2.88 reduction.

 

[gnob]

imo 4.7 is too low for a single case unless all you do is rock crawl. 2.28 low is better for fireroads, in between trails and snow.

 

[Dewil]

Thanks for your input! If I haven’t calculated or thought about it wrong 4,7 gears offer a wider range of gears and less overlapping with “high” gears. I would have 1st low really low and if 5th low is to slow I’ll just put it in 1st or 2nd high.
seems good in theory at least to me.
Question is, is it bad for the driveline to start from a standstill in example 4th gear low?

 

[gnob]

as mentioned, not a good idea to use 5th with the underdrive.
also understand the difference between ratios and torque advantage.

 

[Heretic]

I was reading (somewhere - maybe the Marlin forum?), that it was not good to use the 4.7 gears in the stock xfer case - something about too much torque for the design? I think the inference was that it should be used in the secondary case?

 

[aztoyman]

I have personally tried the 4.7 gears in a single case. It's awesome for crawling but too low for the easier parts of the trail as @gnob mentioned.

I also thought I could just use the higher gears in my transmission to compensate. On paper it looks good but in reality your gears are screaming and I thought something is going to fail if I keep this up. I was "told" that the higher transmission gears aren't made for this.

I already have the 4.7's so I'm still running them. But if I had to do it again I would just go with dual cases with the stock gears and used the 4.7 gear money for the dual adapter.

With stock geared dual cases you can cruise around in the stock low ratio as needed and easily engage the second case and have your super low range. You benefit with a better front drive shaft angle. The trade off is having to shorten the rear drive shaft (relatively cheap) and getting the front re-tubed to be longer. Plus the trans tunnel mods for the shifters.

 

[Heretic]

With stock geared dual cases you can cruise around in the stock low ratio as needed and easily engage the second case and have your super low range. You benefit with a better front drive shaft angle. The trade off is having to shorten the rear drive shaft (relatively cheap) and getting the front re-tubed to be longer. Plus the trans tunnel mods for the shifters.

Also, if one is doing hard 4 wheeling, one should maybe opt for the thicker wall driveshafts (aftermarket) to better handle the torque?

I am also considering the rear wheel disconnect option (Trail Gear) so I have the ability to flat tow my LN172H behind my truck. The alternative would be to go for full floating axles with manual hubs (and maybe disc brakes) - but that is probably more expensive (although the full floating axles would be more robust).

Or, I could do both.

For now, I would stick with what I have and learn whether I think I need the option of adding the extra case, and additional lower gearing. First, I want to level out my pickup; the front suspension is noticeably lower than the rear and I am pretty sure the the shocks are toast. Once I do that I will probably get taller tires, then lockers or LSD. When I have the diffs done, I want to get taller gears; I am pretty sure I have 4.56 diffs, and I think I want 4.1 or 3.9 gearing to give me lower RPM at highway speeds, but taller tires first, then gearing.

 

[Dewil]

as mentioned, not a good idea to use 5th with the underdrive.
also understand the difference between ratios and torque advantage.

That’s why im asking, i don’t understand the difference between rations and torque advantage. I did have a feeling it wouldnt be all benefits lowering the underdrive. Can you explain the difference or Link me to an article? Appreciate the help!

 

[gnob]

im probably not the best to explain.
but for example idle around in 1st gear hi range find an incline to drive. note where it falls off and wants to stall or struggle.
now go 3rd gear low range and try again.
you're getting extra torque from the reduction even though the final drive output is similar.

and stock case is 2.28 not 2.88.

imo if you are serious about it, i think duals are the best route, especially with the 22r.
you end up with 2.28 and 5.19 ratios.
i found even dual stock cases to be a little high for some stuff i wanted to do with the 22re
moving to the 5v made tons more torque and will idle over stuff the 22re would not

 

[Dewil]

I have personally tried the 4.7 gears in a single case. It's awesome for crawling but too low for the easier parts of the trail as @gnob mentioned.

I also thought I could just use the higher gears in my transmission to compensate. On paper it looks good but in reality your gears are screaming and I thought something is going to fail if I keep this up. I was "told" that the higher transmission gears aren't made for this.

I already have the 4.7's so I'm still running them. But if I had to do it again I would just go with dual cases with the stock gears and used the 4.7 gear money for the dual adapter.

With stock geared dual cases you can cruise around in the stock low ratio as needed and easily engage the second case and have your super low range. You benefit with a better front drive shaft angle. The trade off is having to shorten the rear drive shaft (relatively cheap) and getting the front re-tubed to be longer. Plus the trans tunnel mods for the shifters.

Didn’t see your post until now but great info and thanks for sharing your experience. Seems like 4,7 is better in theory than in practice.
I’ll stick with the 2.88 for now and see later on what I will do with gearing. There are plenty of areas that can be covered before that anyway

 

[Dewil]

im probably not the best to explain.
but for example idle around in 1st gear hi range find an incline to drive. note where it falls off and wants to stall or struggle.
now go 3rd gear low range and try again.
you're getting extra torque from the reduction even though the final drive output is similar.

and stock case is 2.28 not 2.88.

imo if you are serious about it, i think duals are the best route, especially with the 22r.
you end up with 2.28 and 5.19 ratios.
i found even dual stock cases to be a little high for some stuff i wanted to do with the 22re
moving to the 5v made tons more torque and will idle over stuff the 22re would not

Thanks for clarifying and also pointing out the correct ratio. I’ll see if I can change my first post so it doesn’t confuse anyone else!