What's Wrong with This Transmission?

So, the Wreck Racing V8 miata finally got the manual transmission it always deserved:

It's a used (and probably a little bit abused) Toyota R154 out of a USDM turbo MkIII Supra. It's installed on our 1UZ V8 with an adapter plate and the original Lexus bellhousing.

Problem: We finally got it up to speed last weekend and it looks like 4th gear is fubar. When I would shift from 3 into 4 it seemed good, until I let out the clutch, then it popped out of gear. If I tried to hold it in gear, it would just grind like crazy. All other gears worked ok.

What are the likely parts that need to be replaced? It isn't the syncro if the shifter moves into 4th, right? I'm thinking the dog teeth on the slider gear and/or on 4th are probably shot. Do you guys agree?

If I'm going to rebuild this, what parts do I need? Slider, and 4th, 4th syncro, maybe the fork? (plus all the relevant seals, while I'm in there) What do you guys think?

Thanks for the advice - much appreciated.

Don't get ahead of yourself!

Wait to get it open and find the problem before you go ordering parts. Problem probably started out with bearing wear from abuse then detent springs then blah blah blah eventually ending up with chewed gears and gruesome things inside your transmission.

Ojala wrote: Don't get ahead of yourself! Wait to get it open and find the problem before you go ordering parts. Problem probably started out with bearing wear from abuse then detent springs then blah blah blah eventually ending up with chewed gears and gruesome things inside your transmission.

Yeah, this is probably best. However, if there's a consensus on what's probably wrong I'd like to order the parts anyway. We can always return them, and we have a track tuning session scheduled in a couple weeks that we'd like to be able to make, so I don't want to spend too long waiting around for the parts.

Well, be sure to poke around because if 4th is out, there's a good chance somebody grinded on some others.

Well he'll...fire up that credit card and burn it up at supra store and marlin crawler! :D

Seriously though, You guys are all young and full of vitamins. If you have a lift there is no reason not to have the transmission out and at least partially torn down today.

Problem is that the root cause might be the main bearing plate or carrier. But that is just the root cause and you don't yet know how extensive the damage is yet.

Is it an expensive junkyard gearbox? If not, that is the only part I'd buy.

Once bits of gear are crunching around in there the whole thing is suspect and if you can spend $250 on another one... to hell with fixing that one.

Giant Purple Snorklewacker wrote: Is it an expensive junkyard gearbox? If not, that is the only part I'd buy. Once bits of gear are crunching around in there the whole thing is suspect and if you can spend $250 on another one... to hell with fixing that one.

Expensive and not so easy to find anymore. Any $250 R154 is going to be trash more often than not.

Ok. Well thanks for the advice guys. I was hoping to hear "oh yeah, it'll just be parts X Y and Z that cause those symptoms", but clearly that's not the case. I'll break it open this week and see what needs replacing.

Aren't the R154 boxes shared with newer GM units?

turboswede wrote: Aren't the R154 boxes shared with newer GM units?

You can bolt a 2jz to a Solstice GXP trans if that's what you mean. I don't know how useful that is in reverse for this application, but it is a thing i guess.

Swank Force One wrote:

turboswede wrote: Aren't the R154 boxes shared with newer GM units?

You can bolt a 2jz to a Solstice GXP trans if that's what you mean. I don't know how useful that is in reverse for this application, but it is a thing i guess.

Still one of my favorite photos ever:

In reply to Swank Force One:

Huh, did not know that.

I do know that the r154 is just one of about a bazillion variants of the Aisin ar5. Just like the h3, Colorado, and canyon transmission. Also the Jeep ax15 nv3550 had the same body to bell pattern.

http://www.naxja.org/forum/showthread.php?t=13106

CRASH said: CRASH >>>>>>>>>>>>>>>>>>>>>>><<<<<<<<<<<<<<<<<<<<<<< As an alternative to the T5, ight I reccommend the Toyota R154 out of the 87-93 Turbo Supra. Some quick (and dirty) info on Toyota transmissions. The Toyota "W" series, "R" series and "AX" series are all built by Aisin-Warner of Japan. Good boxes but with some differences. "W" series consists of the W55, W56, W57, W58 & W59. The only major differences are the gear ratio's used between them. Also, truck versions used shorter input shafts than the passenger car versions. The "R" series consists of the R150F, R151F and R154. These are the heavy duty boxes. They are physically larger that the "W" series boxes. The R150F and R151F were used in Toyota V6 and Turbo trucks. Both 2WD and 4WD. The R154 was used in Supra Turbo's from 87-93. It has a longer input shaft than the truck boxes and came in 2WD only. It also has better gear ratio's than the truck trannies. The AX-15 is a Jeep version of the "R" series boxe. It's case and transmission to bellhousing bolt pattern is identical with "R" series but it also has a much longer input shaft and different tail housing. It came in 4.0L L6 Jeep Wranglers and 3.9L Dodge Dakota V6's. It is considered to be a medium duty transmission but can easily handle most V8 power. The R154 input shaft is less than 1/4" shorter than the AX-15 input shaft and will bolt up to ANY AX-15 bellhousing. Input spline is 1 1/8" X 21. Since any bellhousing that an AX-15 bolts up to, so will an R154. This has some interesting permutations. Photo from left to right: Bell #1: Stock Toyota 3.0L Turbo L6 to R154. Bell #2: Factory AX-15 to Jeep 4.0L six. This bellhousing shares it's engine side bolt pattern with all American Motors 290/304/343/360/401 V8's and can be used to bolt up an R154 to any of them. This particular bell uses an hydrualic throw out bearing. The 94-98 versions used a slave cylinder. Bell #3: Factory AX-15 to Dodge 3.9L V6 in Dodge Dakota pickups. This bellhousing shares it's engine side bolt pattern with ALL Chrysler 273/318/340/360 V8 small blocks. The 3.9L V6 is a 318 V8 with two cylinders lopped off. The R154 can be bolted up to any of them with this bell. Item #4: This is the adapter plate available from Novak Enterprises in Utah. This bolts an AX-15 to any GM 4-speed bellhousing. It can also be used to bolt up an R154 to any Chevrolet/Buick/Olds/Pontiac bell or any bell that works with a Muncie 4-speed. Cost is $295.

More info on R154/AX15 interchange:

http://www.moparchat.com/forums/showthread.php?t=71020

Here's some info on rebuilding an R154:

http://www.supramania.com/forums/showthread.php?33310-Some-R154-Transmission-Rebuild-In-Progress-Pictures&s=5189273538b31d5e106be4fae28f35be

BRB putting a 2jz in my Cherokee.

In reply to turboswede:

Wow, I only knew what I had worked on. I am a subaru guy and I never knew there were so many swap options between for these transmissions.

Damn you people are a bad influence I'm off to Craigslist

Ojala wrote: In reply to turboswede: Wow, I only knew what I had worked on. I am a subaru guy and I never knew there were so many swap options between for these transmissions. Damn you people are a bad influence I'm off to Craigslist

Yeah, I've got a built 2.5L SOHC Chrysler turbo motor in my garage along with a Dakota 2.5L bellhousing. Just need an R154 variant and a chassis to put it in...

Pulled it apart earlier this evening. I still need to check for more subtle damage, but the 3-4 fork was broken and probably bent a bit. This was keeping the slider gear for 4th from engaging all the way, hence the popping out of gear. 4th gear dog teeth and syncro are a little chewed up too, but everything else looks pretty great. Looks to have received new bearings and possibly new syncros in the not too distant past. Also, no metal shavings or bits in the case (except one tiny bit - maybe a piece of a dog tooth), though I think we bought it dry and had only driven it ~10 miles on the current oil.

Case came apart very easily - quite simple compared to the RX-8 6-speed I did a while back.

Here's the broken shift fork:

And the chewed up 4th dogs and syncros:

Here's one of the other gears for reference:

So, here's where I could use some help again. Although this isn't my first time tearing down and replacing busted bits in a transmission, I just don't have enough experience to say how bad those worn dog teeth and syncro teeth are. They look pretty messed up, but I could still get it into gear pretty easily. Now I know that the slider just wasn't engaging far enough and hence the popping out of gear. It would be great if everything was reusable except the fork. (I can wish can't I?) What do you guys think?

Cleaning all that blue crap off would help in judging the condition of everything.

In reply to Kenny_McCormic:

Yeah, I blew it off with an air hose for 5 minutes and wiped up as much as I could with a rag. I guess I'll have to get some acetone or something on there to help wash out the rest of the oil.

I would replace them because they will crunch, but seeing as how you are tight on time and money It might be worth taking a chance to just let it ride.

Could try cleaning up the worst of the dog teeth with a small file if you can't afford to replace them under the budget.

Realistically, you'll only need 4th for the drags and driving on the street. Might be worth spinning the wheel.

I would replace them unless i really felt like i couldnt justify the time/expense of it vs other things. Depends a lot on parts price for me, i guess. Is it $50 or $250?

Vigo wrote: Is it $50 or $250?

Looks like ~$400 from Toyota. Assuming they still have them.

turboswede wrote: Could try cleaning up the worst of the dog teeth with a small file if you can't afford to replace them under the budget.

The car won't be back to the GRM Challenge (We're running it in UTCC this year and it's going to be our road race car going forward), but the club certainly isn't made of money and we do want to keep it as close to the Challenge budget as possible. It does look like there's plenty of material left to file down, so maybe I'll give that a shot.