K-Series Gearbox Question.

[JJT036]

I was talking to Ryan (SLO-030), and I was thinking of this.

 

If I was to keep a 4-speed k40 behind a 4K, would it be worth dragging out the diff ratio to 3.9 or 3.7, OR, get a 5-speed k50, throw in a 4.11 diff ratio, but get the 5th gear cog machined from 0.86 to 0.75?

 

I've tried the theory.......(on Forza 3) and a 0.75 5th gear will mean the Revs will drop on upshift like 1st 2nd 3rd and 4th gear does, rather than just an 800rpm difference. It'd be like 1500-2000rpm difference, and even like the other gears.

 

Ryan said there would be no point in doing the 5th gear modification, because you're only going to blow up your gearbox one day, and I agree with him 100%.

 

I just want to hear other people's opinions and ideas on this topic. :)

 

Josh :cool:

[white_sandshoe]

the key to this question is "behind a 4K"

not the torquiest of engines, taller diff ratios will not make happy in the pants for anyone driving, especially when talking about a 4K 4 speed with 3.7 ratios. 3.9 is ok if you like total grandma style driving, but for something fun and usable (and suited to the K engine) 4.11 and 5 speed would be the way to go, or even 4.3-4.4... My T18s come with a 3.9, and even with the torque of a 3T are still a bit yawn...

And while talking of the lack of torque, a 5th gear mod like that, again, works great in theory... but I'd doubt the 4K's ability to make good use of a ratio that far away from 5th. Unless you do a lot of country distance driving... A lot of it depends on usage...

Yes, it all works in theory, but so does communism.

 

[JJT036]

Thanks for that. :y:

 

I was thinking of it because the 5th Gear is suppose to help with Fuel Consumption on Highway-Driving, but it's only an 800rpm difference to a 4-speed. And to make 5th Gear like every other gear, it would improve the economy even more.

 

By having a dragged out 5-speed, it would mean you still get the same Ratio of 1st to 4th, and a 5th that would be a cruiser gear, driving at 100km/h revving at @ 2500-2800rpm.

 

I know with a 4.5 ratio diff (tested again on Forza 3 -- Redline @ 6000rpm), 1st goes to 40km/h, 2nd = 65km/h, 3rd = 100km/h, 4th = 140km/h, and 5th = 160km/h. But at 100km/h, 4th is revving at 4000-4200rpm, and 5th is revving at 3200rpm.

 

Behind a 4K "Hi-Cam", I know is not the best engine for all this, but it does have Extractors into a 2" system, and it will have a either Jetted 4K Carby, or a 28/32 Weber on it.

 

We live behind the Melbourne Airport, and to Travel to, for example, Church on a Sunday (Glenroy), More than 70-80% of the Drive is 100km/h zones. So it could be under the definition of Country Driving. (Lancefield Rd = 100km/h, Sunbury Rd (and through Bulla) = 60 and 100km/h, Tullamarine FWY = 80 and 100km/h, Western Ring Road = 80 and 100km/h, and Pascoe Vale Road = 60km/h).

 

And having said that, a longer 5th Gear will be great for Fuel Economy, and for cruising. :)

 

Josh :cool:

[ke70dave]

if i understand correctly.

 

you are trying to get a shorter final ratio for more fun in 1st-4th.

 

and then lengthn 5th to get your nice cruise back.

 

you may find that getting individial gears cut will be the deciding factor in this...its not cheap!

 

nice idea though, i would go for a 4.3 rear end if i was going to change it though!

 

there is a toyota spreadsheet somewhere that can do all the speed calcs (so not relying on forza 3). i can't find it on the net (i think i got it from a torrent), if i remember ill upload it when i get home for ya.

[JJT036]

Yeah. What I'm trying to say is:

 

Throw in a 4.11 or 4.3 diff gear, and have a standard 5-speed k50 gearbox and gears, but get 5th machined from 0.86 to 0.75 for better economy and cruising. :)

 

I may, in 5 years time, add an SC14 Supercharger with Intercooler with 8psi to the 4K, with the system like this:

 

Supercharger --> Intercooler --> (Blow-off Valve)? --> 28/32 Weber OR Jetted 4K Carby, with a Decompression plate.

 

Josh :cool:

Edited September 30, 2011 by ewt

[altezzaclub]

Toyota engineers probably worked out all the torque/revs/speed/BMEP figures before they picked that 0.86 ratio, so a lower ratio might not give better economy as you will need your boot down harder. Once you fall off a certain point in the torque curve you will battle to maintain speed. I'd say 3000 to 3100rpm at 100kph would be the lowest to go.

 

Several points involved-

 

Change the diff- I'm in Orange and went to Sydney & back yesterday, so it is all rolling hills with steep bits in the Blue Mountains descent. I'm using a 4.3 auto diff so it is running around 3500rpm in 5th, and when the revs drop to 3000rpm in hills I change down to 4th. That makes it 3300rpm & it pulls well. I don't tow boats or carry 4adults plus luggage, so I don't need low gears, and the nice thing about a diff change is that it moves 1st, 2nd & 3rd up too, so they have longer legs. The 4.1 change is on my list, but you would be using the box a lot if you have a 3.9 and hills.

 

Change 5th gear- That will give you a cruise of 3000rpm using my 4.3 diff, which would be nice, but it would fall off the revs really quickly on a hill. You'd have to change down to 4th and run it at 4000rpm, a big gap like the useless 3rd to 4th currently. Certainly you wouldn't run a 4.1 with a 0.75 5th. The nice thing about this is that it keeps the other gears low so the car is quick around town.

 

Close the box up- I would change 3rd gear actually, moving it closer to 4th. The 1000rpm gap from 3rd to 4th kills the motor in steep country. (Bells Line of Road) To raise 3rd means using an early KE box with a high 3rd and mating that to a 5th gear, or making new 3rd gears

 

The Altezza has a 6speed with all ratios quite close to each other, the gaps shrinking slowly and evenly all the way up. About 600rpm from gear to gear in 4th-5th-6th. To me that is ideal.

 

So overall, move 3rd up towards 4th and either make a 0.75 5th with a 4.3 diff or a 0.80 5th and run a 4.1 diff.

 

Sounds good- make some extras while you're at it!

 

 

 

 

 

 

 

 

 

 

 

 

 

[SLO-030]

+ Rep Altezza!

 

Josh, Get yourself a KR42r Bellhousing and a W58. Because it will be about the CHEAPEST way you will get your desired ratios. And you know you'll never bust it behind a K engine.

 

If anyone here has pulled a K50 apart? The whole counter shaft is 1 piece + a spline right on the end where the 5th gear slots onto the shaft.

 

Making 1 gear different would require a full counter shaft, output shaft to be made. Unless you got the old gearsets machined off of the shafts and attached in the same way as fifth gear..

 

By that time you would have spent easy 1-2k, plus heat treating, grinding, new bearings, seals etc. etc.

Edited September 30, 2011 by SLO-030

[kickn5k]

+ Rep Altezza!

 

Josh, Get yourself a KR42r Bellhousing and a W58. Because it will be about the CHEAPEST way you will get your desired ratios. And you know you'll never bust it behind a K engine.

 

If anyone here has pulled a K50 apart? The whole counter shaft is 1 piece + a spline right on the end where the 5th gear slots onto the shaft.

 

Making 1 gear different would require a full counter shaft, output shaft to be made. Unless you got the old gearsets machined off of the shafts and attached in the same way as fifth gear..

 

By that time you would have spent easy 1-2k, plus heat treating, grinding, new bearings, seals etc. etc.

 

Yep another 1 for altezzaclub and 1 more for you Ryan.

For me I'd be wanting to know what power loss over the k50 the w series gives. Would be a bit more than you'd like in a 4k.

 

1-2k for custom k50 gearsets and shafts, is about right for mates rates. I'm looking into it at the moment mainly because I can't be arsed enlarging the tunnel for a t or w series(the manual KE-1X tunnel is tiny)

Good CnC gear cutters start at about 6-700k so that's where a fair amount of the money goes. Luckily my boss is good mates with a guy that does a fair bit of ARC stuff

 

If your not ripping fat skids or snap changing everygear I'd just use a k50 and adjust gearing and tire size to suit.

The old N/A 5k setup with twin su's used to get around 6.5ltr/100km.

 

Stu.

[SLO-030]

For me I'd be wanting to know what power loss over the k50 the w series gives. Would be a bit more than you'd like in a 4k.

 

Plus rep for Stu too!. One big ol rep-fest.

 

Definatly! The W58 was just as an example, the first G/box I came across that is able to be bolted to a K block and that had similar 5th as to what Josh is talking about

 

But realistically, thats the cheapest option... 500-700 for a W58? 100-400 for a bellhousing. Plus a few other bits like clutch, mounts etc. Say $2k max, you've got an already engineered gearbox, that you know isnt ever going to break with any K engine.

 

As opposed to a $2k K50 that may last 2seconds after you take off down the street.

 

Just play around with diff gears till you get what you like, Piece of piss really.

Edited September 30, 2011 by SLO-030

[JJT036]

Yep. All you guys are 100% correct. + Rep to Altezza, Stu, and Ryan. :yes:

 

For now, I'll just be keeping a standard k40 4-speed, and I'll toy around ideas and thoughts for Diff Ratios.

 

If I was to go for a W58 Gearbox and Bellhousing from a KR42r, should I do a 7K Conversion while I'm at it? Mounting the Gearbox will need some modification, and I thought, IF I do go for the W58 conversion, would a 7K be worth doing as well?

 

And if I do go for a 7K, would I need to upgrade the diff? Celica, Hilux or R31?

 

All of this MIGHT be done (if I choose to go down this path) to Ollie, when I find money and time to do it all.

 

But for now, it's just an idea and thought. :)

 

Josh :cool:

Edited September 30, 2011 by ewt

[altezzaclub]

7K would be a great idea if you grabbed a diff with a 3.7, 1800cc would pull that as a cruise. Get the newest diff you can, Hilux or whatever you find.

[kickn5k]

7K would be a great idea if you grabbed a diff with a 3.7, 1800cc would pull that as a cruise. Get the newest diff you can, Hilux or whatever you find.

That would be awesome would make first gear a bit more usable, tame it down so to speak. But still have the enough torque to pull from 70km/h in 5th!!

 

Oh Ryan your right the W series is the best bang for buck option for a K motor. T series is more than adequate for a K but the bellhousings are a bit scarcer. Let's see how the old K50 likes anti-lag!!

 

Stu.

[JJT036]

7K would be a great idea if you grabbed a diff with a 3.7, 1800cc would pull that as a cruise. Get the newest diff you can, Hilux or whatever you find.

So, would a 7K-ZE + W58 + Hilux Diff = A good combo?

 

If so, I might consider that option for Ollie.

 

Also, would I need to engineer it and/or get a mod plate for it?

 

Josh :cool:

[tojo2]

So, would a 7K-ZE + W58 + Hilux Diff = A good combo?

 

If so, I might consider that option for Ollie.

 

Also, would I need to engineer it and/or get a mod plate for it?

 

Josh :cool:

 

 

Sounds heavy but strong...

 

I went from 3.583 & k40 to 4.1 & k50 in my kp61. It put some life back to the tired 4k.

Milage is fine as well.

 

W58 will need a coustom driveshaft. - not cheap for a decent one.

neither is narrowing a hilux axel

 

If you found a ta22 t50 you could use your current driveshaft and gearbox x.member .Needs k-t bell tho.

(can be bought for us$ 200 from malaisia inc. freight)

 

Diff from same car (6.7") is right width for a ke3

A bit longer nose on them tho so will need driveshaft mod.

 

Just a few more options