What Tranny should I put behind an LSX

I am thinking about resurecting my $2004 Challenge RX-7 as a $2010 car. Since the '04 event the engine and transmission have grown above the Challenge budget. My personal finances this year mean that I need to stay under both the Challenge budget and stay as low as possible for my personal budget. I want to redo the RX 7 using as many of the parts that I currently own as possible. I can remove the current engine and transmission and generate cash for the "personal" budget. It has an aluminum head 350 Chevy w/ ceramic headers and a built 700r4 that should be relatively easy to sell.

So.. what I have available to replace the engine is a 6.0 LQ4. I have 2 LS1 intakes, and the exhaust manifolds, water pump, crank pulley, and injectors from an 01 Trans Am. My dilema is what transmission to use. I have a T-5 from an 87 Mustang and a 4l60e from a 93 Buick Roadmaster. The RX 7 was originally an automatic, which was why I was able to buy it really cheap in great shape. I would love to convert the car to a manual. It would be more fun and the t5 would be easier to adapt to run the speedometer. I have read that the F-Body V8 T-5 cars used the ford bolt patern to bolt the trans to the bellhousing. What would I need to make the Mustang T5 work behing the LSx motor? I know that the T5 isn't likely to last long behing the LSx so please for the sake of this arguement, don't try to tell me that the t56 is way better... I know that it is ... but if you can tell me what bellhousing, flywheel, clutch and hopefully hydraulic throwout bearing would work, it would be a big help.

The 4l60e is probably the easier solution (although less fun), but I also have questions about making the one that I have work. It is an electronically controlled 4L60e, but is an earlier version from an LT1 car. What flexplate and torque converter combination will work? I have the flexplate from both the LT1 and the LQ4, but I only have the LT1 converter.

So I cant really tell, are you building an LSX powered $2010 RX7 or are you just building it for yourself? If for the challenge, I am jealous that you are able to get that nice of a motor in under challenge dollars-could you woo us with the challenge math?

I don't know why a T5 wouldn't work behind an LS. They have held up to STUPID powerful redneck built fox mustangs 302s.

never use automatic!

This is going to sound weird, but have you considered an M5R2 out of a Supercoupe? It's an F150 5-speed manual and Ford installed it because the T5 isn't rated to handle the 330 lb-ft the SC produced. I'll admit I'm not sure about the trans to bell housing bolt pattern and I have no idea what you'd do for a clutch/flywheel combo.

T5 is not going to hold up to LSx power, not without a serious rebuild. Suggested tranny behind an LS1 is a T56, that's what was stock in the F-bodies, or you could try and score one of those sweet rear-mount trannies and torque tubes from a later 'vette (it's not a transaxle).

I'm trying to think of a nice way to mock the idea of a Mazda 5-speed to LSx actually working out without a custom bellhousing or pile of adapter work, etc.

Stock T5 + LS = Kablooie!

The main difference with LS-based trannys and SBC based trannys is the bellhousing depth. The bellhousing bolt patterns differ slightly, but enough bolts line up to make it possible for the swap.

LS-engines have a shallower bellhousing on their trannys, so input shaft length, TC size, and other adaptations would apply. Certainly easy to adapt, but on a challenge budget its easy to blow the whole wad on simple little things.

Car Craft has had a number of really detailed articles on this topic, including one in the last few months on fitting SBC transmissions to an LS engine. Of course, they usually say "buy this awesome adapter" but it'll give you an idea of what's involved.

Does your local library have a subscription?

any regular sbc auto works with flexplate spacer from a 99-00 6.0 - they retained the old style 4L80 for a couple years and just used a spacer and longer bolts to bump the flexplate out to the converter. may potentially need starter too but dont remember.

patgizz wrote: any regular sbc auto works with flexplate spacer from a 99-00 6.0 - they retained the old style 4L80 for a couple years and just used a spacer and longer bolts to bump the flexplate out to the converter. may potentially need starter too but dont remember.

it's tidbits of info like that, that make the GRM forum the biggest win on the internet.

There are a ton of choices based on the old SBC bolt pattern minus one bolt. I don't think the T56 is a great idea, anyway, it's really heavy. Get an old saginaw from the dirt track guys, the kind that had three speeds. Those things can obviously handle the power, and they go for like $75. I should know, I just sold mine. You don't need more than three gears for the challenge anyway.

And Mr. 165 lbs here could bench it.

Keith wrote: Car Craft has had a number of really detailed articles on this topic, including one in the last few months on fitting SBC transmissions to an LS engine. Of course, they usually say "buy this awesome adapter" but it'll give you an idea of what's involved. Does your local library have a subscription?

I am pretty sure I have that article upstairs. If you want, I'll go and scan it for you, or mail you the issue. It wasn't bad.

If you don't want to go to the public library to read car magazines, try carcraft.com. There's a lot of good stuff there, as long as you can ignore their unhealthy obsession with carburetors :)

You can buy a 5 speed 4.8L silverado in the 2000-2005 timeframe. The 4.8 is a gen3 block, so it should all bolt together.

I'm not sure that its challenge budget worthy, but certaintly cheaper than a T56, and might be worth a trip around ebay and car-parts.com to price it out.

MrJoshua wrote: So I cant really tell, are you building an LSX powered $2010 RX7 or are you just building it for yourself? If for the challenge, I am jealous that you are able to get that nice of a motor in under challenge dollars-could you woo us with the challenge math?

Yes I am planning an LSX Challenge car if I can solve a couple of issues economically. The basic budget plan is:

1) '88 RX 7 bought for $350 and Rotary engine and trans sold to Zero out the car. 2) 6.0L Lq4 found on Craigslist for $400. complete except eshaust Manifolds. 3) LS1 intake, fuel injectors, water pump, and exaust manifolds w/ O2 sensors found on Craigslist for $140. 4) Above mentioned Transmissions at "Fair Market Value" I can buy the same 4L60e right now at Pull a Part for $54. 5) Sell the truck Intake and injectors. $50 ish? 6) custom wiring harnesses are available on ebay, $450for the 4L60, $350 for the manual.
7) $150 for a reprogrammed computer

That puts me at between $1050 and $1150, leaving $866 for a driveshaft, motor mount fabrication, and race tires. Should be doable.

I'll check out the Car Craft articles. I have access to back issues. I lnow that the T5 won't last long, but I do have a T5 living pretty happily behing a 330HP 5.0 in a Miata. The light body helps quite a bit. I ran the 1.6 liter Miata rear end in that car for a year, with everyone telling me that the time bomb was ticking, and it lasted with some easy treatment.

traction helps more than the weight. In other words, differentials and transmissions made of glass can live in front of crappy snow tires, or the like. If you're going to drag race this car, it will launch - and that's bad.

The stock rear end has already gone 12.3 @ 113 mph with the current motor and drag radials. But you are right that if the tires break loose before parts break it will be slower but there will be less carnage.

Will wrote: This is going to sound weird, but have you considered an M5R2 out of a Supercoupe? It's an F150 5-speed manual and Ford installed it because the T5 isn't rated to handle the 330 lb-ft the SC produced. I'll admit I'm not sure about the trans to bell housing bolt pattern and I have no idea what you'd do for a clutch/flywheel combo.

I thought the Supercoupe tranny was some ultra-rare Mazda piece, if it's an F150 tranny, that's news to me.

In reply to ReverendDexter:

I think they're the same trans, maybe with revised ratios.

I'm really curious what Mazda was doing with these things, it's really hard to find information on them beyond guys rebuilding them for use in their Rangers or whatever, I'm talking more like history and various applications they showed up in, etc.

I had a 98 F150 with the mazda M5R2 trans in it

Darn! You guys are going with all sorts of serious stuff! I and If I do show up to race at the $2010 Running a 1990 RX7 With 4.30 VLSD from my GTUs 91 Turbo II motor ported and Stock Turbo modified. Stock Turbo II Transmission S5 Aluminum Shaft made to fit NA rear end As for engine management I think I am gonna stick with a Stock ecu with HKS F-Con.

Question** Does a Piggyback Fuel/Timing and Boost controllers have to be figured into the Budget?

junpower wrote: Darn! You guys are going with all sorts of serious stuff! I and If I do show up to race at the $2010 Running a 1990 RX7 With 4.30 VLSD from my GTUs 91 Turbo II motor ported and Stock Turbo modified. Stock Turbo II Transmission S5 Aluminum Shaft made to fit NA rear end As for engine management I think I am gonna stick with a Stock ecu with HKS F-Con. Question** Does a Piggyback Fuel/Timing and Boost controllers have to be figured into the Budget?

You will also want to bring a clutch and maybe a hood along with you, previous Challenge experience states these are commonly replaced items!

junpower wrote: Darn! You guys are going with all sorts of serious stuff! I and If I do show up to race at the $2010 Running a 1990 RX7 With 4.30 VLSD from my GTUs 91 Turbo II motor ported and Stock Turbo modified. Stock Turbo II Transmission S5 Aluminum Shaft made to fit NA rear end As for engine management I think I am gonna stick with a Stock ecu with HKS F-Con. Question** Does a Piggyback Fuel/Timing and Boost controllers have to be figured into the Budget?

Tools or items used on the car that are not on the car during the contest do not count against budget. Certain types of rollbars or cages don't count. Stock quality brake parts don't count. Fluids don't count. Everything else on the car in any part of the competition counts. The things that count are counted at the amount you paid and can verify. If you can't document your purchase price you need to somehow show evidence that the value assigned is reasonable. Finished Ebay auctions, craigslist advertisements, car-part.com listings, etc... work well for this purpose. If all else fails, start a thread posting a description of the part in question and let us determine FMV. Then print out the thread and put it in your budget. Thats the gist of the budgeting process. Their is some weirdness when it comes to trading, but most of it is pretty straight forward and logical.