SC300 Manual Swap Trans Tunnel Boot
 

Hey all, finally getting around to doing my R154 swap on my 93 SC300 hopefully sometime this week. I have a few questions going into it, one I am still unsure of is how much I will have to do to my automatic trans tunnel? I have the floor boot for the transmission for the SC/MKIV but I am unsure how I should mount it. In other R154 swaps i've seen people use a custom fabbed trans tunnel box or a trans tunnel from a different car such as a MKIII Supra. Ideally id like to keep my auto trans tunnel, can i just bolt the floor boot to the auto trans tunnel with room cut out for the shifter?

Picture
 

https://cimg7.ibsrv.net/gimg/www.clu...8b2e0314cd.png
To clarify I have the top Rubber piece and frame, but not the metal Tunnel.

It's good that you've found the upper boot part that bolts directly to the tunnel! That helps with sound and heat isolation.

There are two ways to do this:

A) You can remove the seats, center console and carpeting and then de-weld and de-rivet your SC's original automatic upper tunnel sheetmetal and replace it with an SC M/T upper tunnel sheetmetal part (there is the 92-94 M/T version and the 95-97 M/T version)

B) You can measure where your new manual transmission shifter will come up in your original tunnel and carefully cut into that to create the new shifter opening. Some people fabricate a block off plate with a gasket to cover up the excess hole and some have welded up new sheetmetal in that location. I think the simple custom cover with gasket solution to cover up whatever the new manual shifter bezel doesn't cover is the most popular solution when doing it this way.

Which W58 transmission will you be installing? A 1992-1994 SC300 W58 "toploader" or a 95-97 SC300 & 93-97 MKIV Supra W58 "tripod"?

The 92-94 SC300 M/T tunnel cover part 58260-24020 is now a discontinued part. The 95-97 SC300 & 93-97 MKIV M/T tunnel cover for tripod transmissions (W58, V160/161, R154) and Tremec Magnums is still available and that is P/N 58261-14010.

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There is also the aftermarket manual transmission conversion cover that Grannas Racing makes for MKIV Supras doing a "tripod" style conversion. I believe it will work BUT I strongly recommend you contact them directly and specifically ask IF it will fit SC's and clear our unique upper consoles. On the GrannasRacing website look for "Auto-to-Manual Transmission Swap Tunnel Cover for MKIV Supra".

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Also on eBay through seller "climb-gear" there is a similar SC auto-to-manual conversion cover which looks to be for "tripod" and JZX100 style Toyota manual transmissions. The listing is titled as "FRP Manual Transmission Tunnel panel Toyota JZZ30 Soarer Lexus SC300/ SC400"

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For a 92-94 SC300 W58 "toploader" style transmission you'd either need the 92-94 SC300 M/T tunnel cover sheetmetal or you'll have to cut and modify your tunnel to suit that transmission's shifter location being closer to the engine than it is with any of the "tripod" style manual transmissions.

Wow thanks for the detailed response! I might order that oem part (58261-14010) and see what I can do with that. Also I’m not going with a W58, I found a tripod R154 and bought myself a new bell housing for it to fit my 2JZ-GE. I’m gonna look into all the suggestions you had though, appreciate it man!

https://cimg0.ibsrv.net/gimg/www.clu...ceaf679a2.jpeg
Here she is.

which do you think would work best with my car? It’s a 93 and I’m using a tripod r154. I think the best two options are “RP Manual Transmission Tunnel panel Toyota JZZ30 Soarer Lexus SC300/ SC400” from ebay or the OEM P/N 58261-14010. Which would be better?

Excellent choice! The R154 tripod versions should all have bellhousings that fit 1JZ's and 2JZ's though. It shouldn't need to be changed on that version but looking at your current picture of it you seem to have the correct 1JZ style bellhousing fitted which has the telltale OEM purple paint marking on top.

I ran with my stock engine and correct type M/T ECU and an R154 with an inexpensive OEM Toyota Supra MKIII Turbo 5-speed clutch and pressure plate in California for several years with no issues.

Definitely take advantage of using the cheap OEM Toyota 1986-1992 Supra Turbo 5-speed M/T clutch and pressure plate as long as you have an NA engine up front. With the stock 225hp/210ft-lbs 2JZ-GE and no turbo you won't need any more clutch than that and it'll last a long time :thumbup:

My R154 is from a Supra MKIII which I converted with a factory Soarer R154 shift housing extension (back when they were still available), an OEM 1JZ R154 bellhousing and a custom transmission crossmember using an OEM MKIII Supra R154 mount. The reason I went with the MKIII R154 and took on the extra work to convert it with the Soarer shifter extension housing is because my early 1992-1994 SC300 W58 manual tunnel that the car was manufactured with allowed it to bolt right up. I wanted to modify as little as possible in my case and so I accepted the older style R154 as a way to achieve that.... since that's *almost* the same style of R154 that comes in 1991-1993 Toyota Soarers.

I was able to get away with doing it that way but if I had purchased a tripod R154 I'd probably have gone to the trouble of changing the transmission tunnel with the factory tripod compatible part. That's just how I would have gone about it because I want things as "factory" as I can get them. Changing out the factory transmission tunnel cover with a factory manual cover part is a lot of extra work. Dmitry (97-SC300) did this several years ago with his 2JZ-GTE V160 swapped SC.

These new auto tunnel conversion kits for the MKIV Supra and SC300 respectively are new on the market. They did not exist several years ago.

The part on eBay is around $300 and the OEM tunnel sheetmetal from, say, McGeorge Toyota, is at least 1/2 to 1/3rd of the price.

Replacing the sheetmetal is the most permanent and "factory" way to do it but it requires significant extra work. Not horrible work but the seats, console and carpet among other things have to come out, the old auto tunnel has to be removed and the new one has to be installed. Dmitry (97-SC300) covers this process in great visual detail in his build thread.

Adding on just this conversion piece on top of your existing automatic tunnel is significantly less involved. I am assuming it bolts down in a very sturdy way. So long as that is the case I see no reason not to pursue it. After all, a similar method for MKIV's is sold as a kit from Grannas Racing.

If I were doing it I would replace the sheetmetal. In fact I already have one of those upper M/T tripod tunnel sheetmetal parts in storage in case I should ever need to convert my SC from "toploader" to "tripod". But again, that's just how exacting *I* prefer to be with my own SC.

As long as that FRP upper tunnel conversion part is extremely well made and bolts down securely I think you can go either way.

I wish I had heard some reviews of that "FRP" part by now but it is certainly an option I would at least look into.

Either way the metal of the transmission tunnel has to be sealed from the interior and provide a good mounting location for the rubber dust boots.

You're a fountain of knowledge man! yeah my R154 had no bell housing when I bought it so I had to buy that one on eBay. I also went and purchased the new sheet metal tunnel from McGeorge Toyota so I guess i'm gonna have to rip everything out haha. Thanks for clearing that up man! I will have to look for that thread you mentioned as well.

I thought that was likely the reason you had to buy a new 1JZ bellhousing for it. Replacing the tunnel sheet metal will be a big job but if you want an absolutely perfect factory-style installation that's the way to go so long as you're up for the work to do it.

Here are the relevant build thread posts from 97-SC300's original build thread. Unfortunately all of his picture links seem to be broken now but the descriptions are still there. Note that in his case he was swapping from a tripod R154 to a V160 at the same time he was changing the transmission tunnel sheetmetal. In your case you can disregard all the V160-specific work such as his modifications to the manual shifter bezel. The R154 will have no such fitment issues with the shifter trim bezel.

The V160 (tripod), R154 tripod and W58 tripod transmissions all use that same tunnel sheetmetal in the SC, Soarer and MKIV.

https://www.clublexus.com/forums/per...ml#post7527188
https://www.clublexus.com/forums/per...ml#post7527189

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Aside, are you sourcing out used SC clutch pedal parts or are you going with the XCessive Manufacturing SC manual pedal kit? You will also need to purchase the OEM SC300 manual brake pedal no matter which clutch pedal solution you go with.

Additionally you will need to have your SC300 Automatic front driveshaft modified by a professional driveline shop to fit the R154. It will need to be extended by approximately 50mm / 1.96 inches and then re-balanced with your center bearing and rear driveshaft on a two-piece driveshaft re-balancing machine. The SC rear driveshaft does not need to be re-balanced, just the front driveshaft after it has been modified.

The slip-yoke of the SC300 Auto front driveshaft fits right into an R154 even though as-is it is MUCH too short and will barely engage the splines which will spill transmission oil all over the undercarriage if it is installed without being extended. A true Soarer R154 front driveshaft is rare and very expensive if ever listed for sale and the MKIII R154 front driveshaft also requires some modification to fit the SC properly (it's 3/4" too long). Either the SC300 Auto front driveshaft or Supra MKIII R154 front driveshaft can be modified to the correct length but the cheapest donor part for this will be the SC300 Auto front driveshaft that your car already has. Plus, once the SC300 Auto front d/s length has been changed and a fresh coating of black paint is sprayed on it will look pretty much exactly like a factory Soarer 1JZ-R154 front driveshaft.

https://www.clublexus.com/forums/per...l#post10967561

I can't recall if it was you whom I spoke to recently about the driveshaft solution or someone else. Sorry if I've already covered this with you.

For the most part I’m going with parts from driftmotion. For clutch and pressure plate I’ve gone with just a stage 1R154 clutch kit from driftmotion. I was also going to buy a one piece driveshaft from them once I get the trans in so I can measure the length it needs to be. Also I already have the new pedals and master cylinder installed! Thanks for all your help man, really can’t say it enough!
https://cimg1.ibsrv.net/gimg/www.clu...d1c7d1b3f.jpeg

It looks perfect under there! I'm glad to have helped! All sounds good with your next plans. Aaron @ Driftmotion will take care of you with getting the new driveshaft made. Always great experiences with them! :thumbup:

If I remember right (its been a while), the tripod transmissions will have the shifter come up pretty close to the hole for the original auto transmission.
I think quickgs did this a few times, I want to say just have to make the hole larger.
found it, here is the thread
https://www.clublexus.com/forums/sc-...sc300-why.html

If you had an early manual sc300 92-94, then the shifter hole would be so far forward you would want to swap the tunnel when using a tripod trans.
same if you had an auto and wanted to install an older manual without the tripod, like a mk3 r154 setup.
But for tripod (later soarer style r154) into an auto car, I think you can just cut the hole open larger in the right direction, no need to swap out the tunnels unless you want it to be perfectly oem.

I didn't know the SC Automatic tunnel hole was so close for tripod (or JZX100 style?) shifter location. Maybe this is why the FRP Auto-to-Manual tunnel cover part was developed since only a little bit of cutting is required?

Your notes in that thread you linked say everything, Ali. I wasn't aware it was such a case of "almost fits" with an SC300 Auto tunnel and manual tripod transmission.

It's odd I don't see that many threads of swapping in tripod R154's but I am sure people who do it on auto cars figure it out one way or another.
I think 99SC42 has done every kind of R154 into every kind of SC, I learned a ton from him back in the day but I don't think he is active on the forums much now.

I saw Ali say it above, but in my opinion the 95+ SC300 trans tunnel (JZA80 Supra manual trans tunnel) is basically required for swapping in a tripod transmission [and any other large transmissions] into any 92-00 SC3/400. This gives clearance around the tripod assembly and makes it so the trans has room to "breathe" (aka better airflow around those parts). The earlier SC manual tunnels are good for non-tripod transmissions, while auto tunnels have to be modified (a little or a LOT) to fit ANY manual trans (it's less work to mod to fit a early trans vs a tripod).

Now you can swap any trans into any car and modify your existing trans tunnel to fit. BUT, if you want to seal off the engine bay heat, noise, and exhaust gases like your car came factory manual - use the correct trans tunnel. I can't tell you how many friends I know who have manual converted cars that complain about noises or smells from the trans area that they can't fix no matter how many attempts they do. I think I only know of 1-2 people in the whole Chicago are who did the trans tunnel conversion with OEM grommets and boots and they were very happy with how much it improves things vs before.