Considering going to 3.727 gear/pinion in 6MT

[HotLavaMan]

Originally Posted by smbrm

5th & 6th could be lower on th AT

According to DadHawk, his AT is running at 2350 at 70 MPH whereas my MT is running a bit over 3000 rpm at same speed. That is quite a big difference.

And that is why I'm looking to get the 3.727... it would split the difference between the two.

[Jeff Lange]

Originally Posted by HotLavaMan

I spoke with my local Lexus dealer parts department. It's either a 41039-22010 or 41039-35010 and he's not sure which one would be the correct one. Price is either $172 or $197 and will take about a week to get here from central Lexus parts depot. So more research required.

Jeff Lange, do you have any suggestions on finding out which Lexus part number it would be?

No, those are not what you are looking for, that is the differential internal gear set for a non-LSD open differential. Both of those are the wrong part number. Not sure why they would have looked those up for you.

41201-80050 - Ring & Pinion Gear Set, 3.727:1
41201-80052 - Ring & Pinion Gear Set, 3.909:1
41201-19605 - Ring & Pinion Gear Set, 4.100:1
41201-29606 - Ring & Pinion Gear Set, 4.300:1

Pricing is probably going to be quite a bit higher than what you were quoted for those wrong parts.

Jeff

[HotLavaMan]

Thanks much Jeff. Great info. Do you know if those part kits would also include the appropriate "crush sleeve" (according to my mechanic this would also need to be replaced) or is that yet another part to be ordered?

[Jeff Lange]

The kit includes the ring gear, pinion gear, pinion seal, pinion stake nut, crush sleeve, ring gear bolts and ring gear bolt locking plates.

The 4.300:1 gear kit listed above is for a different model, so the pinion seal is different for that kit. If you went 4.3, you'll probably also need a new pinion seal.

Jeff

[HotLavaMan]

Originally Posted by Jeff Lange

The kit includes the ring gear, pinion gear, pinion seal, pinion stake nut, crush sleeve, ring gear bolts and ring gear bolt locking plates.

The 4.300:1 gear kit listed above is for a different model, so the pinion seal is different for that kit. If you went 4.3, you'll probably also need a new pinion seal.

Jeff

Thanks for all the great info Jeff. Then looks like the 41201-80050 is the one I'm after and has all required parts.

[Jeff Lange]

That's correct.

Jeff

[HotLavaMan]

Local pricing through my Lexus dealer for 41201-80050 is $1106... ouch.

That doesn't include tax and actually having it installed. Hm. I may reconsider priority of changing that out at that price.

[Jeff Lange]

Consider this:

http://www.lexuspartsnow.com/parts/l...201-80050.html

Jeff

[ESBjiujitsu]

this thread is full of good info!!!!!

[serialk11r]

Originally Posted by SpeedR

ya the auto could use lower gearing for better acceleration. I would do this in a second.

Only problem is, you still have the crappy ginormous gap between the ratios, so you will only get marginally better 1st gear acceleration :/

Apparently on some Japanese site the 3.727 gets about 5% better fuel economy on their test cycle, which is probably around what you can expect cruising on the highway. If you drive a lot the savings could add up quickly.

[Calum]

How much gas are people expecting to save by doing this? Why not just disconnect the sound tube after the diaphrame? That would cut down on the noise at least.

[HotLavaMan]

Originally Posted by Calum

How much gas are people expecting to save by doing this? Why not just disconnect the sound tube after the diaphrame? That would cut down on the noise at least.

Well in theory you could on the MT get the same mileage as the AT which would move it from 30 to 34 or about 13% (EPA estimates of course). I don't think it's going to be that high as the total gear ratio will still be shorter than the AT even with the 3.727. But 10% might be within reach.

[serialk11r]

Originally Posted by HotLavaMan

Well in theory you could on the MT get the same mileage as the AT which would move it from 30 to 34 or about 13% (EPA estimates of course). I don't think it's going to be that high as the total gear ratio will still be shorter than the AT even with the 3.727. But 10% might be within reach.

Naw, 3.727 is 10% lower than 4.1, you won't see 10% fuel economy increase from that. The MT revving 30% higher than the AT in 6th is likely worth 10-15% fuel economy depending on speed. 5% would be pretty good already.

[bimmerboy]

+1 this is a great idea, Cruising around 70mph would bring the rpms down a bit as well as lengthen the ratios a little. Should come in handy once power upgrades are available