Re-gearing the diff

[Expat]

In the quest to put larger tires on the 4Runner it is desirable to re-gear the diffs to accomodate.

Does anyone have a contact or info re gearing specialists who could handle this job?

I am currently chasing Oz suppliers for gears for the Prado 120 (same platform) but I find it hard to believe that no-one can cater to the US market in the US.

Just hoping someone has contacts.....

Thanks
Mark

 

[Thai]

I am sure that you know this already...but you have probably a better chance chasing down the aftermarket vendors for the FJ Cruiser: http://www.fjcruiserforums.com/forums/. This forum is vendor-supported so you may find a listening ear if they know that 4runner owners want to re-gear too.

Another FJ forum is: http://www.fjcruiser.cc/forum/. You can try this forum too. It is a branch off the FJ forum above after disputes among the members.

Keep me posted, Mark.

 

[Good Times]

Mark,

I'm working with an US side distributor on the gears for one of the many companies out there. They're in r&d as I've supplied many of the items needed for the r&d and hopefully will have something in the near future. Sadly we're looking like the end of this year or first of the year

as more information becomes available, I'll be slowly releasing those accordingly.

 

[Expat]

Found a company in Oz who can do it. Should have a price tomorrow. They ship to the US and elsewhere often.

Anyone got any good clear pictures of the front and rear diff housings? I need to email them to Oz.

Out of interest we are shooting for 4.56 gears.

Thanks
Mark

 

[Thai]

Out of interest we are shooting for 4.56 gears.

Thanks
Mark

You California guys are just too damn hardcore! Geez, Goodtimes, you, Alex, bulldog, etc. are going nuts on mods!:driving: :bowdown:

 

[trd2001]

Found a company in Oz who can do it. Should have a price tomorrow. They ship to the US and elsewhere often.

Anyone got any good clear pictures of the front and rear diff housings? I need to email them to Oz.

Out of interest we are shooting for 4.56 gears.

Thanks
Mark

wouldnt 4.56 be to low? i was hoping for 4.10 or 4.33's. I miss the stock tires at times.

 

[Expat]

Well, with some math calculations, using the stock tires and gear ratios at 75mph you get 2200rpms and then with regearing to 4.56 you get 2500rpms with 33".

Figure that with the additonal weight of bullbar, camping gear etc, the 4.56 looks about right.

If you were using the truck for a DD and rarely carried heavy loads (eg camping), then I would either a) leave as is ie stock, or b) maybe look at 4.11's (I thought this was the next ratio but maybe 4.10 as per your post above.)

I wouldn't bother to regear for 275's but 285's onwards ie 33-35's then I think it is a wise decision long term.

If you want to follow the technical aspects, maybe check HERE Post no 48.

I think that the time I spend with the 275's the more I have come to notice that I have lost some of the umph that I had with the stock tires. Once I'm loaded down with camping and offroading gear I am conscious of the auto tranny dropping a gear on road inclines that I never use to have the downshift occur when I was off camping. My plan is to go to bigger tires, maybe 34's, once the 275's are worn out, and at that stage I think I will really be hunting the gears. The 4.56 should be just perfect IMO for 33-34" with the additonal weight.

PS - I do use my truck as my DD too, in case anyone was wondering. 1.5-2hrs every day for work.

Cheers
Mark

 

[Expat]

You California guys are just too damn hardcore! Geez, Goodtimes, you, Alex, bulldog, etc. are going nuts on mods!:driving: :bowdown:

Yeah, Lance and Andries are really leading the way with the 4Runner development.

It will be real interesting to see what continues to come out over the next 12 months. Seems like 2 camps are working pretty hard -Lance with a few well-known manufacturers, and Andries with trial and error.

This is all really good for the consumer but also for the companies developing stuff. I am sure that as some of the 4th gens become older and cheaper, people will be buying into the secondhand market with companies prepared to offer a range of goodies that we are still trying to get developed - an example of that is the Shrockworks and ARB Bullbars that has been a real grass-roots effort by consumers demanding the product, as opposed to manufacturers (Toyota and aftermarket) taking the lead eg the FJ Cruiser goodies that are already available!

I just wish I had more money to persue my ideas for a really cool offroad/expedition 4Runner.....sigh!!!

Cheers
Mark

 

[Good Times]

Mark,

I'm not sure what calculations you're doing but that's not adding up to my math that I have on file.

Rpm = mph x gear ratio x 336 / Tire diameter

30.6 = stock diameter tire
33.0 = 33" tires
34.6 = 315/75/16 mtr (as a sample)

75 x 3.727 x 336 / 30.6 = 3069rpm
75 x 3.727 x 336 / 33.0 = 2846rpm
75 x 3.727 x 336 / 34.6 = 2714rpm

75 x 3.909 x 336 / 30.6 = 3219rpm
75 x 3.909 x 336 / 33.0 = 2985rpm
75 x 3.909 x 336 / 34.6 = 2847rpm

75 x 4.11 x 336 / 30.6 = 3385rpm
75 x 4.11 x 336 / 33.0 = 3139rpm
75 x 4.11 x 336 / 34.6 = 2993rpm

75 x 4.33 x 336 / 30.6 = 3566rpm
75 x 4.33 x 336 / 33.0 = 3307rpm
75 x 4.33 x 336 / 34.6 = 3154rpm

75 x 4.56 x 336 / 30.6 = 3755rpm
75 x 4.56 x 336 / 33.0 = 3482rpm
75 x 4.56 x 336 / 34.6 = 3321rpm

75 x 4.88 x 336 / 30.6 = 4019rpm
75 x 4.88 x 336 / 33.0 = 3727rpm
75 x 4.88 x 336 / 34.6 = 3554rpm

Based on these numbers it would look as though that 4.56 would be too low. Of course doing the straight math would yield 3.93 or 4.11 (with 33" tires from 3.727 gearing) being ideal in going back to stock on the mechanical end but factoring the rotational mass involved, going one size lower to 4.33 would be more common. The unfortunate side to this is that I do not know of any vendors that carry 4.33's at all. This would mean that we're either stuck w/ going with the factory Toyota 4.10's or going up to 4.56's when they become available.

Remember that changing gears is to help restore the low end that you effectively lose when getting larger tires. On the flip side, gaining too much low end can have a reverse effect as you will lose the upper end (highway driving) if you are geared too low which would suck for daily drivers that commute on the highway.

As for real world testing on which gears is really the best, I can't say for sure right now. I would suspect 4.56's to be too low for anyone with 33's but I could be wrong. I'd like to see some actual conversions prior to making my final assessment.

Personally I'm still on the fence on which gear set to ultimately go with. Between 4.33's and 4.56's the logical route would yield me 4.33's but the lack of 4.33's right now would force me to the 4.56's which I am not comfortable going there. We'll see as I would like to have my 4runner geared for 33's rather than 35's (as I still run both sizes on a regular basis) which would lead me to 4.33's. Hopefully someone else will go down this path prior to me so I don't have to test the numbers (hint hint Mark! hehe) As bad as running 35's is on the road, it's still doable in that I'm really in no hurry to rush into this. Costs on getting them installed is not cheap and the lack of fund is also pushing me back on this mod.

 

[bulldog-yota]

Lance keep in mind that the transmission has an overdirve top gear. Your calculation assumes that the top gear in the transmission is 1:1, also you use shortened formulas instead of the proper math calculation (close enough but still).

 

[Good Times]

Andries,

Good catch, I totally forgot about that one. Here's the revised numbers.

RPM = (MPH x 5th Gear x Transfer Case Hi x Diff Gear) / (Tire Size x 0.003)

With that you get:

(75 x 0.716 x 1 x 3.727) / (30.6 x 0.003) = 2180rpm
(75 x 0.716 x 1 x 3.727) / (33.0 x 0.003) = 2022rpm
(75 x 0.716 x 1 x 3.727) / (34.6 x 0.003) = 1928rpm

(75 x 0.716 x 1 x 3.909) / (30.6 x 0.003) = 2287rpm
(75 x 0.716 x 1 x 3.909) / (33.0 x 0.003) = 2120rpm
(75 x 0.716 x 1 x 3.909) / (34.6 x 0.003) = 2022rpm

(75 x 0.716 x 1 x 4.11) / (30.6 x 0.003) = 2404rpm
(75 x 0.716 x 1 x 4.11) / (33.0 x 0.003) = 2229rpm
(75 x 0.716 x 1 x 4.11) / (34.6 x 0.003) = 2126rpm

(75 x 0.716 x 1 x 4.33) / (30.6 x 0.003) = 2533rpm
(75 x 0.716 x 1 x 4.33) / (33.0 x 0.003) = 2349rpm
(75 x 0.716 x 1 x 4.33) / (34.6 x 0.003) = 2240rpm

(75 x 0.716 x 1 x 4.56) / (30.6 x 0.003) = 2667rpm
(75 x 0.716 x 1 x 4.56) / (33.0 x 0.003) = 2473rpm
(75 x 0.716 x 1 x 4.56) / (34.6 x 0.003) = 2359rpm

(75 x 0.716 x 1 x 4.88) / (30.6 x 0.003) = 2855rpm
(75 x 0.716 x 1 x 4.88) / (33.0 x 0.003) = 2647rpm
(75 x 0.716 x 1 x 4.88) / (34.6 x 0.003) = 2775rpm

 

[Expat]

(75 x 0.716 x 1 x 4.56) / (33.0 x 0.003) = 2473rpm
(75 x 0.716 x 1 x 4.56) / (34.6 x 0.003) = 2359rpm

There's the money numbers...just right for our trucks with all the additional weight from bullbars etc and greater wind resistance from a lifted truck. I also like the idea of a little more pep from our trucks afforded by this ratio.

I'm getting quite a few no's from the US suppliers so we are still hanging on to the Oz guys to come thru....better go make that call.

Later
Mark

 

[mtnracer]

I thought the 4.56, 4.11, etc only represents the final drive ratio? You can't use that number to calculate the RPM at any given speed. What we need is the ratio for each individual gear. What would each gear look like in a 4.56 final drive ratio? What would be the RPM in a speciific gear at Speed X mph?

 

[bulldog-yota]

I thought the 4.56, 4.11, etc only represents the final drive ratio? You can't use that number to calculate the RPM at any given speed. What we need is the ratio for each individual gear. What would each gear look like in a 4.56 final drive ratio? What would be the RPM in a speciific gear at Speed X mph?

Take you gearbox ratios and calculate if for every gear and tire/diff combo, then you will know. Enjoy

 

[AlexJet]

You California guys are just too damn hardcore! Geez, Goodtimes, you, Alex, bulldog, etc. are going nuts on mods!:driving: :bowdown:

Are you talking about me???? I'm in Toronto, Ontario, Canada. :
I might be nuts, but I like it. There is some major things coming into my list of mods soon....

 

[Thai]

Are you talking about me???? I'm in Toronto, Ontario, Canada. :
I might be nuts, but I like it. There is some major things coming into my list of mods soon....

Shit...sorry...i must have been having a brainfart when i posted that!

 

[AlexJet]

Shit...sorry...i must have been having a brainfart when i posted that!

It

 

[Expat]

Ok. I'll start a new thread Clicky here but just to flag it in this thread too...

I have been able to source 4.56 gears from Australia for $410USD shipped for front and rear ring and pinion.

If you would like to express interest in purcahsing these gears in the future, please indicate in the alternate thread.

I don't know if I can get them any cheaper by avoiding shipping..I am going to Oz in December 06 so maybe I can bring them back then in my luggage allowance for 4 people!

If you have any questions, then post in this thread.

Cheers
Mark