buggy differential question..need some opinions.

[DwightSchrute]

i have a friend that has fallen on some hard times and me and the guys i run with are trying to hook him up with a ride.


we're looking to get him the new ultra-lx-1E. i've done alot of reading on them, and it used to be the ultras had diff issues, but apparently, the new lx-1E's have hardened diff gears and that problem isn't an issue anymore. everyone i've talked to has said they are actually really good on the street and are great for bashing.

so, that being said, i really like all the features except that monster of a spur gear it has. it's a 51t.

my buddy is a bit of a speed freak, so i was trying to find a different spur to pair with the stock diff. no luck there.

my question is...can i swap the center lx-1 diff with an 8ight diff? aren't they all pretty close to being the same?


if anyone can assist, it would really speed along the process.

thanks guys,
-rocket

[skellyo]

51T isn't large for a spur gear...why do you think you need a lower tooth count spur gear?

[lincpimp]

The bearing dimensions are different for the ultra series compared to most other 8th center diffs. Good to hear they have fixed the diff gear issues.

[snellemin]

My GTP uses the same diffs and spur as the LX and I use the plastic 51T spur and still am plenty fast.

[DwightSchrute]

Originally Posted by skellyo

51T isn't large for a spur gear...why do you think you need a lower tooth count spur gear?

Originally Posted by snellemin

My GTP uses the same diffs and spur as the LX and I use the plastic 51T spur and still am plenty fast.

we all own 1/8 buggies, and in the summer we run them at our track, and we do gear it down for the races, but it's a different story when the track is closed..

during the winter we all put in diff lockers and go pavement running. most of us are running 43/24-25 and 44-46/24-25 on 6S. we have a HUGE abandoned walmart parkinglot here where we just chase eachother around and do speed runs.

i'm concerned that the lx-1 won't be able to keep up geared 51/25, and it's no fun if you're the slow guy.

Originally Posted by lincpimp

The bearing dimensions are different for the ultra series compared to most other 8th center diffs. Good to hear they have fixed the diff gear issues.

thanks for checking into the compatibility, lincpimp. anyone have any other suggestions? i even thought about oversized pinions from SDPI, but i'm not even sure the motor mount has enough space for a 30T which is the next available size from 25 or 26T from them, i think.

[snellemin]

Is a higher kv motor not an option?

[DwightSchrute]

Originally Posted by snellemin

Is a higher kv motor not an option?

it is, but we're all running very high kv motors on 6s as it is. the 2650 is what we all use, and that seems to be running right at the motor's limit.

[snellemin]

hmmm, the next thing will be making a custom hub for the solid diff option(OFN33020), so you can run smaller traxxas spurs. This is what I'm going to do with my GTP.

[skellyo]

Originally Posted by DwightSchrute

we all own 1/8 buggies, and in the summer we run them at our track, and we do gear it down for the races, but it's a different story when the track is closed..

during the winter we all put in diff lockers and go pavement running. most of us are running 43/24-25 and 44-46/24-25 on 6S. we have a HUGE abandoned walmart parkinglot here where we just chase eachother around and do speed runs.

i'm concerned that the lx-1 won't be able to keep up geared 51/25, and it's no fun if you're the slow guy.

So let me get this straight...you're running a 2650kv on 6S and gearing it for ~120mph?

I'm quite surprised you haven't melted your motor several times over already. A ~6:1 FDR in a 1/8th buggy is going to put stupid amounts of load on the motor.

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 46
Pinion Tooth Count: 25
Total Voltage: 22.2
Motor KV: 2650
Tire Diameter (inches): 4.3
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0.0035
Spur/Pinion Ratio: 1.84 : 1
Total Ratio: 6.08615 : 1
Tire Circumference (inches): 13.51 inches (343.12 mm)
Rollout: 2.22:1
Total Motor Speed: 58830 RPM
Vehicle Speed: 123.65 mph (198.63 km/h)
Effective KV Value: 2650
KT constant: 0.51 oz-in/A

[DwightSchrute]

Originally Posted by skellyo

So let me get this straight...you're running a 2650kv on 6S and gearing it for ~120mph?

I'm quite surprised you haven't melted your motor several times over already. A ~6:1 FDR in a 1/8th buggy is going to put stupid amounts of load on the motor.

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 46
Pinion Tooth Count: 25
Total Voltage: 22.2
Motor KV: 2650
Tire Diameter (inches): 4.3
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0.0035
Spur/Pinion Ratio: 1.84 : 1
Total Ratio: 6.08615 : 1
Tire Circumference (inches): 13.51 inches (343.12 mm)
Rollout: 2.22:1
Total Motor Speed: 58830 RPM
Vehicle Speed: 123.65 mph (198.63 km/h)
Effective KV Value: 2650
KT constant: 0.51 oz-in/A

actually, you're not far off. most of us have already gotten over 95mph and a few of us have broken 100mph when it was a bit warmer with the grp rally tires.

Originally Posted by snellemin

hmmm, the next thing will be making a custom hub for the solid diff option(OFN33020), so you can run smaller traxxas spurs. This is what I'm going to do with my GTP.

excellent idea. i'll look into that. thanks a bunch!

[lincpimp]

Keep in mind the diff ratio is 44/14. So with the 51t spur and a 25t pinion you get:

Differential Ratio: 3.142857142857143
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 51
Pinion Tooth Count: 25
Tire Diameter (inches): 4
Rollout: 1.96


Std buggy diff ratio, 46t spur and 35t pinion:

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 46
Pinion Tooth Count: 25
Tire Diameter (inches): 4
Rollout: 2.06


Std buggy diff ratio, 43t spur and 25t pinion:

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 43
Pinion Tooth Count: 25
Tire Diameter (inches): 4
Rollout: 2.21

So not a huge difference to a 46/25. I would not worry.

[DwightSchrute]

Originally Posted by lincpimp

Keep in mind the diff ratio is 44/14. So with the 51t spur and a 25t pinion you get:

Differential Ratio: 3.142857142857143
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 51
Pinion Tooth Count: 25
Tire Diameter (inches): 4
Rollout: 1.96


Std buggy diff ratio, 46t spur and 35t pinion:

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 46
Pinion Tooth Count: 25
Tire Diameter (inches): 4
Rollout: 2.06


Std buggy diff ratio, 43t spur and 25t pinion:

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 43
Pinion Tooth Count: 25
Tire Diameter (inches): 4
Rollout: 2.21

So not a huge difference to a 46/25. I would not worry.

i had no idea the ultra lx-1e had a diff ratio that high. that changes everything. i gotta crunch some more numbers, but i think that might be the way to go. thanks!

[snellemin]

yes, the LX has the same diffs as the GTP. But the smaller spur mod will be a good idea still for an even greater topend.

[lincpimp]

My first buggy conversion was a lx. Way back when...I had no idea what I was doing. Plus I was using maxamps and feigao back then. At least the motors were cheap! 7xl on 4s lipo! I blew those diffs up frequently. K series diffs are not the best, that is for sure.

[Semi Pro]

Originally Posted by lincpimp

My first buggy conversion was a lx. Way back when...I had no idea what I was doing. Plus I was using maxamps and feigao back then. At least the motors were cheap! 7xl on 4s lipo! I blew those diffs up frequently. K series diffs are not the best, that is for sure.

where you shimming them back then linc?

couldnt you just toss in some hotbodies diffs?

either way couldnt you guys just buy him a used 8ight on ebay for $100-$150 then he could share parts with you too