4.88 vs 5.29

I'm confused why 5.29's would be considered too much for a factory tire. I've run the numbers in comparison of a 6speed auto with 4.30 gears vs. a 6 speed manual with 4.30 gears, and the final drive and rpm @ any mph from 4th gear and up are almost identical. So if 5.29's are too much for a factory tire would it be safe to say the 6 speed auto is undergeared and the 6 speed manual overgeared from the factory?

 

Factory gearing, especially the OD gears, are selected to compenstate for both driveline power loss (auto loses a bit more) and meet EPA MPG mandates.

The are not really selected for future vehicle modifications or even your driving pleasure.

Since tire dia is a factor in final drive ratios, the reason 5.29 is a bit much on OE tire sizes is it raises cruising RPMs a good bit higher. Normally that's selected to offset the installation of a taller tire that has reduced the final drive ratio.

 

I understand. I guess the real contemplation I have is the rpm's my motor will have on it with 5.29 gears. I was concerned, having a 2.7. Then I saw the factory specs for a 5speed 2.7 running @2800rpm in 5th gear @80mph from the factory, which is a higher rpm than any 3rd gen Tacoma application. Switching over to the comparison of 5.29's in a 6sp auto vs the 6sp MT being comparable, I have to wonder why 5.29 would be too much for a 2.7L.

 

And what would the RPMs be with 5.29, OE tires and your 6spd.?

Only you can decide if you want to cruise at those RPMs and reduced MPG in your truck.

 

The comparison above was for the 2.7L 6sp AT vs the 3.5L 6sp MT with 4.30 differential gears and factory tires. The results are almost the same, save that the 2.7L may run a little higher rpm in real world applications, though it seems that Toyota intended the 2.7 to run a little higher rpm judging by the numbers of the 5sp 2.7 application coming out at a higher rpm than any other platform released for the 3rd gen.

 

There is no way the final ratio of 5th and 6th can work out to be the same between a 5.29 and a 4.30 without a gearing change in the transmission to compensate.

If your grimmjeeper calcs are assuming the only change is the axle ratio, their last two calcs are wrong on the 5.29 side.

 

I believe it is because the gearing in the transmission is different. Look at the specifications of the gearing between the two in the chart above and then see after I inputted those numbers into the calculator the final drive and the rpm@mph from 4th-6th work out to be almost the same. That's my conundrum.

 

Ok. Only solve for the transmission you have, not all the others.

 

It seems that the majority of the transmission issues, being undergeared and not utilizing both overdrives correctly comes from the 6sp AT. This is the same transmission I have. 6sp AT are the same for 2.7 and 3.5, so the transmission gearing is the same. The only difference is the pinion gear. I'm just curious if the 5.29 was too much, then why would Toyota release two applications; (2.7L 5sp MT, and the 3.5L 6sp MT to run at a higher or equal rpm than either a 3.5 or 2.7 AT with 5.29 gears?

 

put my two cents into this discussion!

cent 1. Get gears.
2020 OR AT with 275/70/18 Grabbers 32” ish from Toyota brand new 78km on the odometer and levelling block in the front. Drove it for two weeks. Crap mileage. It was winter and I went and got new nokian hakkapeliitta stubbed same size. Got better mileage but still crap. Three week ago I got 5.29 gears installed and I just got the best mileage I have ever had in this truck hands down. Not even a question in my mind. I have been driving in town as well as highway driving at 65 in Alaska. Have BF ko2 same size tires. I also have a brand new C4 not cut bumpers for the last full fuel tank. I notice the bumper weight every time I stop. Almost want to upgrade the front brakes side note. I can’t image the bumper helps with fuel mileage at all. I did notice the mileage as soon as I left the shop that installed the gears right off the hop. I have been tracking the Mileage gauge in the truck from day one. Nov 30 2019. Now that I have done one and half tanks With the gears and bumper the mileage has been impressive. It will never be my pre diesel gate VW mileage, but it is better then it was. I am sure you might get better mileage with 4.88, but right now I would say don’t bother if you have 32” with 4.88. Don’t take my word for it. I am sure you will be happy with either one. I run between 2100 and 2200 on the highway. I also seem to be in that spot a lot more in town as well.

cent 2
I believe I am noticing that the gearing seem to be helping with with the transmission gear searching. Why I can’t tell you. Maybe the force with a purple lightsaber. I am still monitoring this to confirm.

The truck is seems brand new again as it is so different. It seems like a true truck now.

 

Birks I appreciate the feedback about your application. I don't run as heavy with my rig as you, but this is definitely some good insight on what I could expect from 5.29's.

 

I run 5.29’s on 285’s. For stock tires you can run 5.29 for sure, but 4.88’s would be more ideal I would think.

 

No problem. I am not planning on adding anymore weight other than a GFC if I ever gets built. they say that is 275lbs I believe. Of course plus gear.

The bumper is probably more than what I will ever need. It was covered by insurance, as a bird did a kamikaze dive into my truck and put a full blown hole in the stock bumper. So I figured why pay for a bumper just to get it cut. I prefer no cut anyway.

 

If you wouldn't mind next time you take a drive, would you take note of the new shift points with the 5.29's? I'm curious what rpm the truck is shifting at in each gear now.

 

I just had 5.29s installed last week and I can tell you at 65mph I'm at 2100 rpms. Today I watched it shift into 4th at 25 mph. I'm also running the 5.29 OVTune which changes shift points.

 

Sure I can do that. No ovtune on my truck.

 

I'm glad to hear they have the 5.29 OVtune. Do you know if that applies to the 3rd gen 2.7L? I hear OVtune just recently cracked the ECU for the 3rd gen 2.7L, though I believe they are not doing tuned ECU's, rather releasing a flash tune platform that is end user programable.

 

The tune Im using is 3.5L specific, I'm not sure if he's doing the 2.7. But I do know he tunes Tundras and Lexus's, so he might have one in the works.