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Discussion Starter · #1 ·
I put a Driftmotion rebuilt R154 into the car about 4 months / 1500 miles ago. i have a Cube short shifter on it and the clutch is a Clutchmaster twin disc.
I am having a hell of a time downshifting into second gear. Upshifting and downshifting through any other gear isn't an issue and engages smoothly. Even with rev matching i feel like i am forcing it into second when going down from third. There is no grinding with the shifts just the need of some extra force to get it in.
looking for some input on what might be causing this. Do i just need to do a better job of rev matching?
 

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I have had an R154 for years. Mine was a zero miles rebuild when I got it. I will say that the biggest issue I had was downshifting into 2nd. I went through 3 shifters until I ended up with the Driftmotion one. I love that shifter cause it almost eliminated the problem. The R is a known finicky trans. In the cold, (Chicago winters) it’s noisy and hard to shift until it warms up.
Now I will say I’m still not the best heel and toe guy but I started getting good enough to do it at the track and that’s when the problem reappeared. I had the same problem you described. I think it just might be a problem due to the high speed difference of the synchros. On the street mine is fine.
 

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Under what conditions is a change-down into 2nd difficult? For example, are we talking engine braking where you're at 4500 in 3rd, meaning that you'll be 6000rpm in 2nd? Or perhaps you're coasting in neutral approaching a stop light - but the light turns green while you're still rolling so you need to just slip into 2nd and go? Or maybe your cruising at 3000rpm in 3rd but want to accelerate hard so you change down into 2nd? Or maybe any/all of these conditions?

I rebuilt my R154 and it was not finicky at all - in any gear under any circumstance. In fact it was way better than W55 on a change down into 1st.

That said, mine had this style shifter on it:



The actual shifter I had was a modified cheapie chinese "short shifter" for IS300 that I got off eBay
 

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I had the downshifting into second problem to the day I got rid of it. I had a cube shifter as well which I thought was pretty good so I don't believe thats the problem.

Something that I've found completely puzzling is that my transmissions, both the R154 and the AR5, shift MUCH better when cold instead of when warm. The will be way smoother in the morning as opposed to when I'm driving in traffic where they will be all notchy and noisy. At this point I've just accepted it, I love the feeling of my morning transmissions.
 

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If the transmission shifts differently warm vs cold - you should try different lubricants to find one the trans likes best.

I've experimented with this in the past quite a bit and it can make a big difference.

Don't get too wrapped around the axle following exact manufacturers guidelines, either.

If there's nothing wrong with the shifter or shift mechanism - a difficult shift without grind points to insufficient friction between the synchronizer cone and the speedgear cone. I've had success putting some clutch-type limited slip differential "friction modifier" into the trans to make the synchs grab better.
 

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OP, do you have the early or late version of the R?
The updated R had a 3 piece synchronized 2nd gear and better shifters.
The USA version was the early version found on MK3 Supra’s, the JDM versions were the better ones.
 

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For reference, my R154 was an early model with the one piece synchs - but the replacements I put in had the revised "wedge tooth" asymmetrical teeth.
 

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Discussion Starter · #8 ·
guys, thank you for all the good info.
it is happening in all instances, when i am engine braking, downshifting from a coast, or downshifting to get higher RPMs to accelerate. there is no difference between any of these scenarios. i do feel like as i slow down (and RMPs decrease) that i can get it to engage easier. hodgdons point about friction between speed gear and synchro makes sense and adding some friction modify would be an easy place to start. anyone else have thoughts on this?
I was also thinking it could be the shifter but i feel if it was this i would have the same issue with up shifts as i do with down shifts.
how do i tell what version R154 i have?
Automotive tire Gas Asphalt Motor vehicle Engineering
 

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That tailshaft housing/shifter housing arrangement makes it the early style.

I agree with your rationale about ruling out shifter as the cause, on account of it changing up to 2nd from 1st not being an issue.
 

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Yup that looks like an early model. I still don’t think you should be having that problem especially on a brand new rebuild.
Take this with a grain of salt but some old timers (fellow mechanics) would run cheap oil on fresh rebuilds then drain after 1K or so miles and refill with good oil.
As far as the friction modifier, it’s an easy try like Hodgdon said. Just use one that’s safe on synchros (pretty sure they’re brass on our trans) as LSDs obviously don’t them.
 

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guys, thank you for all the good info.
it is happening in all instances, when i am engine braking, downshifting from a coast, or downshifting to get higher RPMs to accelerate. there is no difference between any of these scenarios. i do feel like as i slow down (and RMPs decrease) that i can get it to engage easier. hodgdons point about friction between speed gear and synchro makes sense and adding some friction modify would be an easy place to start. anyone else have thoughts on this?
I was also thinking it could be the shifter but i feel if it was this i would have the same issue with up shifts as i do with down shifts.
how do i tell what version R154 i have? View attachment 138915
Early model.

I don't think its the shifter itself but it's worth ruling out, get the easy stuff out of the way up front.

As to hodgdon's point I'm all for. The issue ALWAYS felt synchro related and in my current AR5 I still feel some resistance and slight grind here and there, and it's practically brand new so go figure. On my end I run Redline but am looking at changing to Amsoil as I have heard nothing but good things.
 

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Just use one that’s safe on synchros (pretty sure they’re brass on our trans) as LSDs obviously don’t them.
Ah, the famous GL4 vs GL5 controversy! This is what I meant earlier when I wrote:

Don't get too wrapped around the axle following exact manufacturers guidelines, either.
I've followed gearbox video on the 'tube for quite some time, and I've spoken to him a number of times on the phone. I trust his input a lot. Here's what he says about various viscosities and GL4 vs GL5. The discussion begins @ 11:22. My take-away has always been to experiment with different fluids and perhaps mixtures and see what works. As far as I know, I've never hurt a transmission by doing this.

 

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Ah, the famous GL4 vs GL5 controversy! This is what I meant earlier when I wrote:



I've followed gearbox video on the 'tube for quite some time, and I've spoken to him a number of times on the phone. I trust his input a lot. Here's what he says about various viscosities and GL4 vs GL5. The discussion begins @ 11:22. My take-away has always been to experiment with different fluids and perhaps mixtures and see what works. As far as I know, I've never hurt a transmission by doing this.

I know that was a big deal years ago but I’m not necessarily talking about that. I will watch that video later at home but Toyota themselves state you can run GL4 OR GL5…
I’m talking about people running dog tooth trans fluid in a synchro box and other such things.
I run MT90 because most everyone agreed it improved shifting over whatever came stock/they had before. If someone comes out with something better I’m not opposed to it.
 

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I ran/run MT90 as an attempt to change/improve shifting but did not notice a change in my AR5/R154 boxes. I ordered Amsoil recently and will change to that whenever I get the chance to.
 

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I ran/run MT90 as an attempt to change/improve shifting but did not notice a change in my AR5/R154 boxes. I ordered Amsoil recently and will change to that whenever I get the chance to.
I'm a fan of Amsoil Torque Drive manual trans fluid. That's what I had in my R154 and what's in the T56 magnum now.
 

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may not help but i run mt90 in my high mileage w55 and it made it feel like new when shifting, also make sure our clutch pedal is adjusted correctly.
 

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I also run MT90 or MTL depending on which I can find at the time on all my Toyota manual transmissions for the last 10-15yrs. It normally makes a huge difference in the smoothness of your shifting, cold or hot.
 

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Update. Just took the car out for the first time in a while, had to charge the damn battery. Low gas so first thing I did was fill it up at 3.96. Calculations yield a frosty 18mpg.

Drained transmission, Redline MT90 looked good as new. Replaced with Amsoil and did notice a small diference, nothing earth shattering, but it does shift better. Hopefully by putting some more miles on it, it will lubricate even better....although at these gas prices I'm perma-using the mr2 or outback.
 
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