Hi , i have a 1981 toyota 4x4 with a 4 speed transmission (engine is 2.2L Diesel with an L45 gearbox) and i am trying to do a 5 speed conversion since i am going to put larger tires on it (31.5 or 33's still not sure) and so having a 5th gear would help a lot because with larger tires i am afraid that the gears will become too low and so i would kill its already low top speed.

I already read the other posts about the conversion but i am still unsure. i already bought a power steering from this guy who has a 1991 toyota 4x4 by the looks of it, it will mount with no problems (haven't installed it yet). Now the thing is i asked him about his gearbox and went to check it out to see if it might fit mine. Problem is his engine is a 2.8L Diesel Engine and from the marlin website it shows that the 4x4 of that time came out with W56-C gearbox and from the threads I've read they only state that either L50 or L52 will fit my engine.

Do you think it would be possible to put my gearbox housing onto that one or has anyone ever done this (or knows if its possible or not). He told me that his housing fits onto the 2.4L and since gearboxes from the 2.4L Fit mine i figured i should ask to see if it's possible.

Thank you for your time and opinion i appreciate it.

 

These are 2 shots of the gearbox i mentioned (the W56-C )

https://www.flickr.com/photos/128666...5/15542763751/

 

Wouldn't larger tires mean taller gearing?

 

Just changing from 4-speed to 5-speed won't help you.

In order to run taller tires, you'll likely need lower final drive gears.

4 speeds are 1-1 ratio in high gear. As far as I know, Toyota 5-speeds are all 1-1 ratio in 4th gear, and 5th is overdrive.

 

the 5 speed box will help your freeway speeds and get rid of the sloppyness inherent in the L45 selector.

we don't see a lot of diesels in the US so can't tell you exactly what transmissions will bolt up to a diesel.

generally recommended gearing choices for 33's = 4.88's
35's= 5.29's

 

yes that is the idea , i know that the L50 and L52 gearing is identical to the L45 but it has an additional 5th gear and that will help reducing revs , that is mostly what im looking for. for the most part the truck will be daily driven so if i can reduce stress on the engine and transmission i think it would be better. im currently running 28" tires and they do fine but since upgrading by an additional 3-5 inches i think i would be shifting every 2 seconds. (Diesel Engines have less bhp then the 22r you guys have ) so i think the 5th would help a lot

 

I think you are seeing this wrong, with the bigger tires you will be shifting less, driving at higher speeds with lower revs. For example, let's say now you are at 2500 rpms at 60 mph with your 28'' tires, you'll be at 2000 rpms at 60 mph with 33'' (numbers used only as an example) in the same gear, 4th.

 

hmm , i always thought that reducing the tire size would increase speed and increasing the tire size would reduce speed but gain torque.

my theory is based on motorcycles (you increase the sprocket size to gain torque and reduce sprocket size to gain more top speed.

since with 28" the circumference would be smaller and with certain rpm it would rotate as much but with bigger tires it would take more revs to go around 1 revolution of the larger tire

i am not 100% sure about this because im very new and since i ride a motorcycle i never have to worry about this stuff so im sorry if i may sound stupid.

 

It's not too bad, it's just the oposite of what you thought Look for a gear ratio/tire size calculator on google and you can check the difference in speed and rpm you'll have with the bigger tires that should help make your decision for a transmission.

 

ok so i have read from several websites explaining how this taller tires thing works and you are right. i finally understood how it works , so now basically my problem will be torque since i have ''increased'' top end i will now be lacking torque because it takes longer to accelerate. and my engine is only like 67bhp so ill have to see how it works out. ill try to lend a set of tires to see how it goes with my engine/gearbox and then move on from there i guess

 

It might be better (or less worse) for you because you have a diesel. If not you will have to change the gearing in the diffs. I would love to fit a 6 speed transmission to a 22r one day, like from an rx-8 or something. Best of both worlds!