To re-gear or not to re-gear? (1 Viewer)

[Octupus AUH]

14 minutes ago

Hi All, My name is Zak messaging you from the UAE and hoping that i can get some help.

I own a 2021 LC200 and very interested in modifying the gear ratio from stock and want to get more clear information about the expected results:

The engine is 5.7 V8 and 8 speed automatic.

Im not able to get a clear idea about the results of increasing my tire size and regearing.
My current tyre setup is 285/70r17 and im planning to increase to 315/70r17 (34.4 in diameter)
on the highway the car struggles to stay in 8th gear at our cruising speeds ~140kmh (87mph)

Can you share with me the following;
1. some clear information about expected results of the regear with the tyre sizes
2. a comprehensive parts list for the install, i have found links for the ring and pinion Ring and Pinion Gear Set - UZJ100/URJ200/LX570 Rear Axle Gears - 4.88 Ratio (TOYLC488R200) - https://cruiserteq.com/ring-and-pinion-gear-set-uzj100-urj200-lx570-rear-axle-gears-4-88-ratio-toylc488r200/ however I saw some webpages saying it needs more parts
3. recomendations about 4.30 or 4.88 in terms of the best ratio.

 

[linuxgod]

Yes as you increase tire size your RPMs will be lower and the transmission may need to downshift to maintain power, especially at speeds >80mph. Bigger tires will only make it worse

There are threads about the 2016+ vehicles with the 8 speed and what's required, but the short answer is you probably want 3.90 gears, not 4.30 or 4.88. The 6 speed came with 3.90 from the factory, but the 8 speed uses 3.30 gears. A ~25% increase for the 3.90 crowd are 4.88s, but for you a ~25% increase is 3.90.

 

[Octupus AUH]

Yes as you increase tire size your RPMs will be lower and the transmission may need to downshift to maintain power, especially at speeds >80mph. Bigger tires will only make it worse

There are threads about the 2016+ vehicles with the 8 speed and what's required, but the short answer is you probably want 3.90 gears, not 4.30 or 4.88. The 6 speed came with 3.90 from the factory, but the 8 speed uses 3.30 gears. A ~25% increase for the 3.90 crowd are 4.88s, but for you a ~25% increase is 3.90.

Thanks Geoff Thats very good information, i was not aware about the ratio difference between older and newer models or the existence of 3.9 gears.
Could you help me with an online source to order all of the parts?

 

[linuxgod]

Thanks Geoff Thats very good information, i was not aware about the ratio difference between older and newer models or the existence of 3.9 gears.
Could you help me with an online source to order all of the parts?

I don't have a parts list as I have a 2013. There are a few threads around here, or maybe even earlier in this one, where people have done it.

partsouq.com is your friend for tracking down official part numbers for various model years, but IIRC there's some difference in the 3rd member housing