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The Double S
A lot of older threads on the topic of marrying transaxles to V8s. I just finished rebuilding an LS1 and am looking to weigh current and cost effective options on the trans. G50s are out of my league but Boxter and Subaru variants sound efficient and reliable. Currently running a SBC 350 and 901 side shift.

For those of you who have had the experience of building them, or are building them now, what are your opinions, preferences, or realizations?

Planning for a street/track set up. Thank you for the help in advance.
tygaboy
To your point, it's about budget. I have an LS3 and I didn't want to worry about things breaking so I went with a Boxster S 6-speed (G86-20) as they've been proven to about 500 hp.
They can be found on ebay in the $2k range. You can get a stock shifter and cables for a couple hundred, last I looked.
Kennedy Engineering makes the adapter plate, flywheel and clutch. Or you can get the whole kit, including trans mounts from Renegade, but it's not cheap.

Best of luck with your decision.
horizontally-opposed
QUOTE(tygaboy @ Sep 13 2020, 01:55 PM) *

To your point, it's about budget. I have an LS3 and I didn't want to worry about things breaking so I went with a Boxster S 6-speed (G86-20) as they've been proven to about 500 hp.
They can be found on ebay in the $2k range. You can get a stock shifter and cables for a couple hundred, last I looked.
Kennedy Engineering makes the adapter plate, flywheel and clutch. Or you can get the whole kit, including trans mounts from Renegade, but it's not cheap.

Best of luck with your decision.



Chris, is the proven to about 500 hp with V8s or flat sixes or? Curious as the later 981 GT4 6MT signed off on by Motorsport was limited to 310 lb-ft, which arrives at 4700+ rpm in that car. The gearing is pretty bad in a 981, too, with 2nd stretching to 84 mph and 3rd to 112 mph—so not too fun on a back road.

I've started to wonder about taking a 7MT from a 991 and flipping the ring gear as people do with 915 gearboxes, as the torque limit is higher. Next question is whether there's a way to delete 7th gear or lock it out like Porsche does on the GT4 Clubsport PDK, or just enjoy 9,000,000 miles per gallon.
The Double S
QUOTE(tygaboy @ Sep 13 2020, 01:55 PM) *

To your point, it's about budget. I have an LS3 and I didn't want to worry about things breaking so I went with a Boxster S 6-speed (G86-20) as they've been proven to about 500 hp.
They can be found on ebay in the $2k range. You can get a stock shifter and cables for a couple hundred, last I looked.
Kennedy Engineering makes the adapter plate, flywheel and clutch. Or you can get the whole kit, including trans mounts from Renegade, but it's not cheap.

Best of luck with your decision.



Thank you. Did you rebuild the transaxle once you received it or run it as is?
tygaboy
QUOTE(horizontally-opposed @ Sep 13 2020, 02:19 PM) *

QUOTE(tygaboy @ Sep 13 2020, 01:55 PM) *

To your point, it's about budget. I have an LS3 and I didn't want to worry about things breaking so I went with a Boxster S 6-speed (G86-20) as they've been proven to about 500 hp.
They can be found on ebay in the $2k range. You can get a stock shifter and cables for a couple hundred, last I looked.
Kennedy Engineering makes the adapter plate, flywheel and clutch. Or you can get the whole kit, including trans mounts from Renegade, but it's not cheap.

Best of luck with your decision.



Chris, is the proven to about 500 hp with V8s or flat sixes or? Curious as the later 981 GT4 6MT signed off on by Motorsport was limited to 310 lb-ft, which arrives at 4700+ rpm in that car. The gearing is pretty bad in a 981, too, with 2nd stretching to 84 mph and 3rd to 112 mph—so not too fun on a back road.

I've started to wonder about taking a 7MT from a 991 and flipping the ring gear as people do with 915 gearboxes, as the torque limit is higher. Next question is whether there's a way to delete 7th gear or lock it out like Porsche does on the GT4 Clubsport PDK, or just enjoy 9,000,000 miles per gallon.


Pete - I was only concerned about what to use with my V8. The LS3 in my car came out of Tony's (Cracker) 914 (also running a G86-20, though he does have an LSD) and was replaced with an LS7 that dyno'd at something like 530hp at the wheels. He tracks his car so regularly sees WOT and his trans is taking virtually all that power. To date, he hasn't had any gearbox issues. I think if you don't abuse it, it'll last, especially on the street.
For fun, here's Tony on track with the LS3 before I got it.
http://www.914world.com/bbs2/index.php?showtopic=271085
tygaboy
QUOTE(The Double S @ Sep 13 2020, 03:37 PM) *

QUOTE(tygaboy @ Sep 13 2020, 01:55 PM) *

To your point, it's about budget. I have an LS3 and I didn't want to worry about things breaking so I went with a Boxster S 6-speed (G86-20) as they've been proven to about 500 hp.
They can be found on ebay in the $2k range. You can get a stock shifter and cables for a couple hundred, last I looked.
Kennedy Engineering makes the adapter plate, flywheel and clutch. Or you can get the whole kit, including trans mounts from Renegade, but it's not cheap.

Best of luck with your decision.



Thank you. Did you rebuild the transaxle once you received it or run it as is?


I got it via ebay, it had only 56k miles on it and the car it came from wasn't damaged at all anywhere in the back half. I've decided to give it a try as is. That said, I've only just gotten my car running. It was aligned and corner balanced two days ago and still needs some help with ITB and ECU tuning.
Give me a few weeks and I'll have a full road test report!
horizontally-opposed
QUOTE(tygaboy @ Sep 13 2020, 04:01 PM) *


Pete - I was only concerned about what to use with my V8. The LS3 in my car came out of Tony's (Cracker) 914 (also running a G86-20, though he does have an LSD) and was replaced with an LS7 that dyno'd at something like 530hp at the wheels. He tracks his car so regularly sees WOT and his trans is taking virtually all that power. To date, he hasn't had any gearbox issues. I think if you don't abuse it, it'll last, especially on the street.
For fun, here's Tony on track with the LS3 before I got it.
http://www.914world.com/bbs2/index.php?showtopic=271085


Tony's car is incredible, and I remember watching one of his Road Atlanta videos in a kind of awe. Looks like he's clean and smooth, FAST with mechanical symphathy. Perhaps Porsche's point about the GT4 6MT being at its torque limit already with the 2016 model has to do with their torture tests—which may be their way of anticipating certain…customers.

Down that road, I was in a Porsche shop years ago and a guy came walking in saying I owed him a transmission for his 993. Why, I asked? Because, apparently, I had said that his 993 had a strong transmission. He went on to say he had killed his transmission after some hard starts (5000 rpm and dumping the clutch). "Ah," I said. "I meant that transmission can probably withstand 24 hours of racing at a place like Daytona..." as I scratched my head and considered the fact that he had just gotten out of a Ford Lightning pickup.

"Strength," and "limit," can mean different things...and sounds like you'll be just fine.
ri914
I chose an LS6 with the renegade kit. super happy but I am not driving it yet as I started the build 2 months ago. lots of body work to do.

did I hear the 2nd gear in the boxster S tranny goes to 84mph? what is the top speed in 6th?
horizontally-opposed
QUOTE(ri914 @ Sep 13 2020, 06:13 PM) *

I chose an LS6 with the renegade kit. super happy but I am not driving it yet as I started the build 2 months ago. lots of body work to do.

did I hear the 2nd gear in the boxster S tranny goes to 84mph? what is the top speed in 6th?


I'd have to dig into 986 gearing, but 981 gearing was a bit of a mess—to the point I wanted to have a shift knob made for my GT4 that said:

2-4-5
3-5-5

These figures for the 981 GT4 given match up with my experience:
1st = 46mph
2nd - 83mph
3rd = 118mph
4th = 150mph
6th = 183mph

The ratios were frustrating in the GT4, as there was no need to shift on the majority of backroads, and the GT4's shifter is one of the main attractions. They also seemed to really blunt its in-gear quickness 2-3-4. Meanwhile, 6th left you turning 3200-3600 between SF and LA where a 991 7MT drops the revs down to 2200, greatly increasing its comfort as well as its fuel range, while its 2-3-4 stack are really nice for a back road.

In a 914, the lack of a need to shift might be a bonus. Engine types matter, too.

I had a couple of 986 Boxsters, and preferred the 2.5 5MT gearbox to the 2.7 setup, as it was a bit shorter (in some ratios, I think) to make up for the 2.5's lesser torque. The 986 6MT was pretty nice on the street, iirc.

Supposedly, 987.1 6MT is:
1st = 30mph
2nd = 70mph
3rd = 99mph
6th = 172mph

EDIT: Found charts below, which may be helpful. The one on its own for "Boxster S: Transmission diagram" is for the 986 Boxster S 3.2
djway
QUOTE(tygaboy @ Sep 13 2020, 04:01 PM) *

QUOTE(horizontally-opposed @ Sep 13 2020, 02:19 PM) *

QUOTE(tygaboy @ Sep 13 2020, 01:55 PM) *

To your point, it's about budget. I have an LS3 and I didn't want to worry about things breaking so I went with a Boxster S 6-speed (G86-20) as they've been proven to about 500 hp.
They can be found on ebay in the $2k range. You can get a stock shifter and cables for a couple hundred, last I looked.
Kennedy Engineering makes the adapter plate, flywheel and clutch. Or you can get the whole kit, including trans mounts from Renegade, but it's not cheap.

Best of luck with your decision.



Chris, is the proven to about 500 hp with V8s or flat sixes or? Curious as the later 981 GT4 6MT signed off on by Motorsport was limited to 310 lb-ft, which arrives at 4700+ rpm in that car. The gearing is pretty bad in a 981, too, with 2nd stretching to 84 mph and 3rd to 112 mph—so not too fun on a back road.

I've started to wonder about taking a 7MT from a 991 and flipping the ring gear as people do with 915 gearboxes, as the torque limit is higher. Next question is whether there's a way to delete 7th gear or lock it out like Porsche does on the GT4 Clubsport PDK, or just enjoy 9,000,000 miles per gallon.


Pete - I was only concerned about what to use with my V8. The LS3 in my car came out of Tony's (Cracker) 914 (also running a G86-20, though he does have an LSD) and was replaced with an LS7 that dyno'd at something like 530hp at the wheels. He tracks his car so regularly sees WOT and his trans is taking virtually all that power. To date, he hasn't had any gearbox issues. I think if you don't abuse it, it'll last, especially on the street.
For fun, here's Tony on track with the LS3 before I got it.
http://www.914world.com/bbs2/index.php?showtopic=271085

Wow that shifts nice drooley.gif
ri914
QUOTE(horizontally-opposed @ Sep 13 2020, 10:37 PM) *



I'd have to dig into 986 gearing, but 981 gearing was a bit of a mess—to the point I wanted to have a shift knob made for my GT4 that said:

2-4-5
3-5-5

The 986 6MT was pretty nice on the street, iirc.

Supposedly, 987.1 6MT is:
1st = 30mph
2nd = 70mph
3rd = 99mph
6th = 172mph

EDIT: Found charts below, which may be helpful. The one on its own for "Boxster S: Transmission diagram" is for the 986 Boxster S 3.2


Great info, I guess I got lucky buying the G86.20 6 speed. Not that I know a lot now but when I bought it I had no idea.
dwillouby
I have an 04 Boxster s 6 speed behind my LS2.

Used the Kennedy adapter package and the Renegade trans mount.

Not cheap but good quality parts.

If I recall I paid $1,400 for the trans.

Got a shifter & cables on ebay for ~$170.

Don't really use 1st as starting in 2nd seems perfect for the LS.

Shifts like a new car.

David
Mueller
If money was no object..Xtrac transmission.

Guessing 10's of thousands of dollars.

cali914
QUOTE(Mueller @ Sep 14 2020, 11:21 AM) *

If money was no object..Xtrac transmission.

Guessing 10's of thousands of dollars.



Looks to Pretty to put in the car.
The Double S
QUOTE(dwillouby @ Sep 14 2020, 10:15 AM) *

I have an 04 Boxster s 6 speed behind my LS2.

Used the Kennedy adapter package and the Renegade trans mount.

Not cheap but good quality parts.

If I recall I paid $1,400 for the trans.

Got a shifter & cables on ebay for ~$170.

Don't really use 1st as starting in 2nd seems perfect for the LS.

Shifts like a new car.

David


Thanks David. Was your trans an ebay purchase? Did you rebuild before install? Also did you do the work yourself?

Army Roger
Same set up I'm starting with on my new 914 project. LS3 from Summit Racing, Boxster S 6 speed, along with KEP and Renegade/Hybrib products. This is my first post and I'm so happy that I found 914World.com........Roger, U.S. Army, stationed in Germany right now.
mepstein
QUOTE(Army Roger @ Sep 15 2020, 04:05 PM) *

Same set up I'm starting with on my new 914 project. LS3 from Summit Racing, Boxster S 6 speed, along with KEP and Renegade/Hybrib products. This is my first post and I'm so happy that I found 914World.com........Roger, U.S. Army, stationed in Germany right now.

Thank you for your service and welcome.png
djway
Several mentions that the KEP adapter and Renegade mount are Pricey. Pricey is a relative term, how about a rounded dollar amount?
tygaboy
http://www.renegadehybrids.com/
Gearup
I have an LS1 and Boxster S. Go with Stuttgart Muscle for Adapters and Spec 2 clutch. I personally feel it is better quality than Kennedy or Renegade and for less money. Google the company.
The Double S
QUOTE(tygaboy @ Sep 15 2020, 05:50 PM) *


I've reviewed Renegade's page a number of times trying to make sense of some of the figures. It's an investment for sure. Does the basic kit include trans?

On the flip side, I've heard nothing but good things about their kits. I'm looking into their cooling package also. It's said to be second to none by many people that have them.
The Double S
QUOTE(Gearup @ Sep 15 2020, 05:58 PM) *

I have an LS1 and Boxster S. Go with Stuttgart Muscle for Adapters and Spec 2 clutch. I personally feel it is better quality than Kennedy or Renegade and for less money. Google the company.


Thanks for the info Gearup. I actually ran across this company awhile back and forgot about them.

What was an indicator that the parts were better quality?
dwillouby
You can buy the parts from Kennedy.

Renegade just resells them.

LS to Boxster adapter & flywheel $1850

Clutch package $850

David
The Double S
QUOTE(dwillouby @ Sep 16 2020, 10:32 AM) *

You can buy the parts from Kennedy.

Renegade just resells them.

LS to Boxster adapter & flywheel $1850

Clutch package $850

David



Has anyone sourced the mounts from a company other than Renegade?
Mueller
QUOTE(The Double S @ Sep 16 2020, 11:15 AM) *

QUOTE(dwillouby @ Sep 16 2020, 10:32 AM) *

You can buy the parts from Kennedy.

Renegade just resells them.

LS to Boxster adapter & flywheel $1850

Clutch package $850

David



Has anyone sourced the mounts from a company other than Renegade?


Fabricate your own might be the only other option other than Renegade.

It seems the total price is only going to vary about a grand or so just purchasing all the parts. (bought conversion specific parts)
dwillouby
Renegade has the mounts made for them.

Their mount is very well made.

Others have made there own mounts.

Check with Bigkat83.

He helped me with my questions when I started my conversion.

David
The Double S
QUOTE(dwillouby @ Sep 16 2020, 02:24 PM) *

Renegade has the mounts made for them.

Their mount is very well made.

Others have made there own mounts.

Check with Bigkat83.

He helped me with my questions when I started my conversion.

David


Good to know. Thanks David.

What about axles? Are there a variety of options out there?
tygaboy
Axles will depend on what you do at the hub. If you stay with 914 stub axles, you can get axles with Boxster inner CVs/914 outer. Renegade sells them, as do others, I assume.

With the LS, I wanted as strong a set up as possible so I went with late Carrera hubs and 911 e-brake set up. I run standard late Carrera axles, as pictured. To work with the Boxster S trans, you need a 1/2" spacer between the inner CV and output shaft (make one or you can pruchase from Renegade), and accordingly longer inner CV bolts. There is also a spacer that goes over the splined end of the axle (available from Patrick Motorsports).

NOTE: since the "stub axle" no longer lives with the trailing arm (when the axle isn't in the car), you aren't supposed to put weight on the trailing arm bearings without the axles installed. (not necessarily torqued, but they should be in there to roll the car around, etc.)
This makes it a bit of a pain to work on things when the trans is out, since you have to leave the axles installed and supported.
tygaboy
@The Double S - You should make the trip up for the 2020 WCR in Petaluma on the weekend of November 5. I live in Petaluma and hope to have my car at the event. But even if I don't make that, you'd have a chance to come to my place and check out my set up.
dwillouby
With my setup I am using the early 911 cv's & the 5 bolt stubs.

To mount to the Boxster flanges I drilled out holes for the 2 roll pins in the cv to allow the use of 6 bolts at the flange.

Got my axles from Pacific Customs 22" IIRC.

Check out Tygaboy's work, you will be impressed.

David
The Double S
QUOTE(tygaboy @ Sep 17 2020, 07:20 AM) *

@The Double S - You should make the trip up for the 2020 WCR in Petaluma on the weekend of November 5. I live in Petaluma and hope to have my car at the event. But even if I don't make that, you'd have a chance to come to my place and check out my set up.


Thanks Tygaboy. If I can get up there I definitely will. Sounds like you have it dialed in. I appreciate it.
The Double S
As I have been researching this over the past year it seems like the G86 transaxles have been the go to for most recent repowers.

Has anyone dabbled with Subaru options? Or any other creative thoughts with cost and functionality in mind?
Mueller
QUOTE(The Double S @ Sep 18 2020, 12:58 PM) *

As I have been researching this over the past year it seems like the G86 transaxles have been the go to for most recent repowers.

Has anyone dabbled with Subaru options? Or any other creative thoughts with cost and functionality in mind?



http://www.subarugears.com/Adaptors/Adaptors.html

Unless you make your own parts, all of the transmission options are going to be close.


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