Tech:Drivetrain/Bellhousing

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Recently it has become much easier to source upgraded Bellhousings. Here are some of the common ones with information on how / where to obtain them if at all possible.

In a nutshell, people are finding more power from smaller Toyota engines, this extra power tends to break things, the next thing in line after your engine is your gearbox. Rather than buy six million gearboxes for every time you know you will break one, it may be wise to consider upgrading to a stronger Gearbox.


In Terms of strength in Toyotas, the more common boxes are (very generally) ordered here from Weak to Strong.


Weak

K40, K50 (used on K series engines)

T40, T50 (used on T and A series engines)

W50 (different to W5x - used behind R and M? series engines)

W55, W56, W57 (Used on Celicas and Supras)

W58 (Supra Turbo etc)

R154 (Turbo Supras / Soarers etc)

Strong

I found an article that compares the Toyota gearboxes which was apparently scanned from Street Commodores magazine originally and can be found [[1]]

Things to keep in mind / Disclaimer

  • Bigger is NOT always better - putting an R154 behind a K series engine is hardly going to be affordable or worthwhile
  • Flywheel & Starter - Remember also that you need to find out what flywheel and starter motor are best suited to use with the upgraded bellhousing.
  • Tailshaft - If you upgrade your gearbox, chances are that you will need a stonger replacement tailshaft or possibly have yours modified / customised
  • Diff / Axles / etc - Remember the weakest link of your drivetrain dictates how much power you can put to the ground. If you keep blowing up gearboxes, chances are that after you upgrade your diff is going to shatter with that big horsepower going through it, it might be time to think about upgrading that as well ;)
  • Brakes - Ok well this isn't part of your driveline but I couldn't help but add something here about making your monster-engined-whatever STOP when you hit the brakes. This is something which is too-often overlooked and as far as I am concerned the thing most overlooked in engine conversions. Safety FIRST, not second!


K to T

Now that people are milking out 160 horsepower from the K series engines, it is clear that the K40 / K50 box is becoming the weak link. Fortunately for us, Toyota saved us the hassle and actually made a FACTORY K-to-T bellhousing. This was used in the KT140, KT141, KT142, KT147 series Corona's and KE74 corolla wagon (as far as I know only JDM or Jap import into New Zealand) which came from the factory with a 5K-U hooked up to a T40 gearbox! Swap it over to a T50 and this is quite a sensible package


K-To-T is the perfect upgrade for those who have lost faith in the strength of K series gearboxes. I myself have recently purchased one privately for $205 New Zealand Dollars / $184 Australian Dollars / $138 US Dollars from Trademe.co.nz which doesn't include shipping.


Availability : Second hand there are quite a few on the ground in New Zealand, and using Trademe.co.nz will be your best option at this stage. I have not yet heard of aftermarket (brand new) manufactured K-to-T's but there would probably be someone out there who would have produced them by now if you searched hard enough.

K to W

This is starting to borderline overkill! A W55 gearbox is nearing 43kg alone, to go completely overkill you can use a KR## van bell housing which has a G5# gearbox behind it to adapt a K-engine-to-W5x box. As it is the W55 that is known to be able to withstand 300+ horsepower of punishment, a far cry from the best of 165+HP from a K series engine that I have seen proof of. The other W box, the steel case W50 can also be adapted using the earlier KM20 van bell housing which has a cable clutch L40 box behind it. (same bolt pattern as the steel case W50).


Availability : A KM36 or KR3# series townace van has the K-W bellhousing, these will bolt up to a W series supra alloy box with only a change from cable to hydraulic clutch.

A to T

Standard equipment behind all RWD 4age engined cars, ie AE86's, AA63 celica and Carina, AT141 corona. Theres also the 2nd version with clutch fork on the L/H side that come in aussie 4a-c AE71 or jdm 3a-u AA60 celica. Bellhousing is removable. Not an upgrade as such, but worthwhile mentioning :)

A to W

Never produced by toyota, but there are a few aftermarket manufacturers so probably available second hand all over the place. You have to love aftermarket go-fast-bits and bolt-ons!


Perfect upgrade for anyone looking to put a stonger box behind a particularly rambunctious 4A-GE / 4A-GZE / 4A-GTE / 7AFE / 7AGE / 7AGTE etc etc. With claims of being able to handle upwards of 300 horsepower with ease, the W55 style gearbox is what you want.


Sources:

I am aware of a source in Malaysia that can supply these for approx AUS $~400 landed anywhere in Mainland Australia, but unsure if this offer is still being extended to anyone else. also Dellow (Australia),(research their feedback before purchasing heh), Nite Parts (NZ), Conversion Components (NZ).

S to T

came fitted to jdm SA60 celica, possibly ST14# corona. also available aftermarket mostly used in kitcars like the fraser clubman.

S to W

Factory fitted behind jdm 1S and 2S engines in SA6# celica, ST14# corona with a W55. these need to be modified to fit a 3S(GE) block because the gearbox input shaft does not reach the spigot bearing. The diesel C series engine 1C/2C have an identical bellhousing with a W box behind it. But interestingly most commonly found in vans with a 1C or 2C engine and G series gearbox (G52, G55) which has same bolt pattern as the supra W55 box. Other bellhousings have been known to be adapted like the 2Y/3Y to W bellhousing by slotting some holes.