New 5th gear for the R154 - how about a taller overdrive?

[Nick M]

Yep. I built it specifically for my cross-country trip to Wyoming this summer My goal is to push 30+ MPG from the Supra on the highway

I don't think it is going to happen. Not without a custom tune. Stock is too rich. My A340E and 91 couldn't do it with cruise control at 70mph. Ford did it by using an extreme lean cruise program, and a NOx front cat with an air pump. GM too for that matter.

What is missing is what speed you are using in the opening post. I can do the math, since I know the formula. But I want to be spoon fed.

I like your project, and am in agreement. A T56 would be best, but requires work and money.

 

[Nick M]

Playing with fourth means messing with 3rd as well, for me. That's why I wanted to do something custom in an R154.... any more info you have to reveal?

Yes. 4th is direct drive, the input and output shaft are connected together. Hence, dyno pulls in 4th.

 

[got_boosted]

Used to get +/- 29 mpg in my all stock '88 NA 5spd hard top cruising avg. 70mph. Hoping that my 86.5 hard top sport package w/ a 2JZ-GE > R154 > lightweight 1pc shaft > 4.30LSD will do better (and be a lot quicker lol).

I'm interested in this mod!! How'd you like to rebuild my R154 for me?

Collin

 

[Guyana00]

Ummmm 4th isn't actually a gear so NFI how you're going to "play" with it.....

I understand what you mean Ian, lol, you and your wordplay. I deserve that though. Fourth would be a 1:1 ratio still with the main drive gear locked to the output shaft. I was referring to changing the main drive itself. Either way, I should have explained more, you caught me



I'm not starting anything Dow, all I was saying, was when I drive I shift fourth gear at 3,000 RPM and I cruise around at about 2,000 on the streets at around 70km. Lower that 2k in fifth my car starts to bog. If the ratio for fifth was lower than that when I shift at the same rpm in fourth I won't be able to go the same speed at 2000 rpm in fifth. To go 70 I'd have to stay in fourth.



That's all I was saying, I want to see how it works out for you though because as I said I always wanted to re-gear the R154.

 

[got_boosted]

I understand what you mean Ian, lol, you and your wordplay. I deserve that though. Fourth would be a 1:1 ratio still with the main drive gear locked to the output shaft. I was referring to changing the main drive itself. Either way, I should have explained more, you caught me



I'm not starting anything Dow, all I was saying, was when I drive I shift fourth gear at 3,000 RPM and I cruise around at about 2,000 on the streets at around 70km. Lower that 2k in fifth my car starts to bog. If the ratio for fifth was lower than that when I shift at the same rpm in fourth I won't be able to go the same speed at 2000 rpm in fifth. To go 70 I'd have to stay in fourth.



That's all I was saying, I want to see how it works out for you though because as I said I always wanted to re-gear the R154.

At 70km/h, roughly 45mph, I would definately expect it to bog in 5th gear. However at ~70mph, highway cruising speed for me here, 5th is almost a power gear lol. As stated in my previous post, my 88 NA got amazing fuel economy with stock gearing, but I believe that it could benifit from a slightly lower cruising rpm.

Collin

 

[SupraClaou]

I think that 0.6 5th gear would be to much,....to long.
We would need about 500+ whp to go through that gear.It will decrease
the accelaration in 5th dramaticaly. Even stock 3.7 rear is quite long.
It will only be good for those that will put 5th only for cruising & max.economy.
I wouldn't recomend this 'mod' for those who wanna push the pedal to
the metal in 5th fear.

My opinion it would be nicer to make a custom 3.5 rear ring & pinion
since no one is making this anymore!

Only my 0.02 cents :biglaugh:

p.s. I am really interested in a 3.5 rear ring & pinion.

 

[tissimo]

I see no need for it.

 

[Doward]

All calculations done @ 70 mph, lol - sorry - updated the first post

If you're worried (and it's a 0.66 not 0.60) about acceleration in 5th gear with a 3.73 rear gear setup, don't buy one then. Swap a 4.30 diff in and get back to me

A 3.73 / 0.66 setup would be GREAT for someone just looking to cruise in their Supra. A 3.91 / 0.66 setup would be a very good compromise for a street machine.

The big fun would be the 4.30 / 0.66 - all the acceleration of the 4.30s, with almost the gas mileage of the 3.73s

I might be doing some rebuilds on the r154s when I offer this - but that will only be 2-3 at most.

 

[got_boosted]

Thanks for clarifying the 70mph speed and ratio.

Only slightly off topic, but I'm sure that many in this thread will be wondering as well: I've rebuilt a few manual transmissions in the past, so I'm familiar with what's involved, but I have been wanting to ask somebody who has done it a few times; are there any R154 specific tricks or special tools that I should know about before cracking it open?

Thanks,
Collin

 

[Moy]

Doward it's too I don't live near you, I could have you re-vamp the R154 I have sitting on my garage floor right now and let you know the results of a taller 5th with 4.30's :evil2:

 

[SupraMan1987]

I'd be interested as well, as I planned on picking up an extra 154 and building it for that nice tight feel again. Are their going to be any bearing changes, or just the gear? I also would like to know if any Toyota SST's make it easier, as I think I could gain access to them if it makes it that much easier.

 

[Dirgle]

In due to interest. The level my RPM's sit at during highway cruises drives me batty. I was thinking about swapping to a 3.73 diff but this would give me more of what I'm looking for. I'm also running a 2jz with stock twins, as such the boost comes on early and it has a lot of torque down low. I doubt your 5th gear would be to long for it. So for my setup your fifth combined with my 3.91 is exactly what I'm looking for.

 

[Doward]

I've designed this all around my own car with 3.91 gears, but I'll be testing it on a 3.73 equipped car (let you guys see it at the lowest possible RPM)

The 4.30 guys will probably be all over something like this, lol!

The gear set is a literal drop in replacement for the stock 5th gear. Nothing else is required.

Any transmission rebuild I do, however, will be the 'total package' - bearings/synchros/thrust washer/blueprinted setup.

 

[sneakypete]

this is good stuff... subscribed

 

[Zumtizzle]

DAMN YOU DOWARD.

The transmission is going to have to come out again!

 

[IJ.]

I ran the .68 5th in my TKO with 4.30, 4.10 and 4.11 diff gears and with tall tires it was getting up there ratio wise to what a 3.0L in a fat car is happy to cruise at.

.66 should work ok just remember it's a tiny pair of cogs and won't take a lot of abuse if you have a lot of power.

 

[SupraMan1987]

I'd be interested in a set for sure. What do you do when you blueprint it all? Just tighten all clearances up, or what? Curious, as it means different things to different people.

 

[Guyana00]

The big fun would be the 4.30 / 0.66 - all the acceleration of the 4.30s, with almost the gas mileage of the 3.73s

That's what I was thinking :icon_bigg

I do also want to see it with a 3.73 in a mkiii used for longer trips and highway usage since most people go 120 on the highway (km) the RPM would be nice and low and with a nice tuning adjustment it would give some great gas mileage!

 

[Doward]

I'd be interested in a set for sure. What do you do when you blueprint it all? Just tighten all clearances up, or what? Curious, as it means different things to different people.

I check every single thing in the transmission. Every clearance, every measurement, the whole 9 yards.

And then I go over it with a fine toothed comb

Good example - i didn't like the way my nylon spacer looked in my transmission - replaced with new. All snap rings are in nice and tight, with no play in anything.

I'm looking forward to seeing what basically a brand new R154 feels like

All new bearings / seals / synchros, and going to have Redline MTL in it

 

[SupraMan1987]

Any ballpark estimate on price for your rebuild Doward? I could do it myself, but if you don't want to rape me on cost, I'd love to have it done by someone who has cracked a 154 open before. I don't mind building trannys, but this one will catch hell, and I don't want it breaking on me.