First Post to say Hi

[San Diego GTR]

I just sold my Factory Five Racing Cobra and am looking forward to my next project, an Ultima GTR. My daily driver is an '06 ZCP M3. I would love to know if there are any other GTR builders/owners anywhere close to me. I am contemplating using an LS7 powerplant and am unsure which transaxle would be the best to mate that with. I am leaning toward a Getrag. Does anyone have any thoughts on the above?
Thanks,
Paul

[steve_d]

Welcome Paul
Your first port of call should be Ultima Club US.
The site has a map of US showing where all the members are located. Not all have an Ultima but may be in the same situation as yourself.
I think most will be using the G50 'box primarily because it is almost impossible to modify or repair the Getrag.

Steve

[bluesatin]

Porsche 911 turbo (996) with X50 option or GT2 getrag gearbox are repairable and significantly stregthened.

[Hugger Z]

Paul,
From the US gathering this past September, a 6-speed trans is recommended for fuel economy reasons on any trips. I think that would be the turbo trans, but am not positive.

[steve_d]

Hugger Z said:

Paul,
From the US gathering this past September, a 6-speed trans is recommended for fuel economy reasons on any trips. I think that would be the turbo trans, but am not positive.

6 gears does not bring you an economy advantage only an improved ratio will do that.
The 6 speed G50/20 (US only) having a ratio of .755 is best but the most common choice 5 speed 'box's are the G50/50 & G50/52 both of which are only slightly worse at .756.
The 6 speed G50 turbo is worse than that at .790.

However some are now putting a higher ratio gear (.688) in the 6 speed box which will make a considerable difference.

Steve

[Hugger Z]

steve_d said:

Hugger Z said:

Paul,
From the US gathering this past September, a 6-speed trans is recommended for fuel economy reasons on any trips. I think that would be the turbo trans, but am not positive.

6 gears does not bring you an economy advantage only an improved ratio will do that.
The 6 speed G50/20 (US only) having a ratio of .755 is best but the most common choice 5 speed 'box's are the G50/50 & G50/52 both of which are only slightly worse at .756.
The 6 speed G50 turbo is worse than that at .790.

However some are now putting a higher ratio gear (.688) in the 6 speed box which will make a considerable difference.

Steve

I understand that. I meant that the extra, taller gear allows better economy for the long trips. I know the 6th gear in the stock GM boxes is something like 0.5 and that gets me 28-30mpg in my car. Just as a benchmark.

[steve_d]

Hugger Z said:

......I meant that the extra, taller gear allows better economy for the long trips. .......

Perhaps you missed that the top gear ratio in the 6 speed 'box is no better than top in the 5 speed so there is no economy advantage between them.

Steve

[Hugger Z]

steve_d said:

Hugger Z said:

......I meant that the extra, taller gear allows better economy for the long trips. .......

Perhaps you missed that the top gear ratio in the 6 speed 'box is no better than top in the 5 speed so there is no economy advantage between them.

Steve

Got it. I was just going off of what was discussed at the US gathering this past September. A few of the guys had upgraded from the 5-spd to 6-spd box. Maybe they had a 5-spd box without a taller top gear. I know there are a bunch of variants out there.

[steve_d]

Hugger Z said:

steve_d said:

Hugger Z said:

......I meant that the extra, taller gear allows better economy for the long trips. .......

Perhaps you missed that the top gear ratio in the 6 speed 'box is no better than top in the 5 speed so there is no economy advantage between them.

Steve

Got it. I was just going off of what was discussed at the US gathering this past September. A few of the guys had upgraded from the 5-spd to 6-spd box. Maybe they had a 5-spd box without a taller top gear. I know there are a bunch of variants out there.

My understanding is that the aftermarket replacement gear (.688) can be used in a 5 or 6 speed as the new top gear.
In our application with the Chevy motor there is so much torque that a 6 speed box offers no advantage. One owner used an early Porsche box with only 4 gears and it worked fine with big long pulls in each gear.

Steve

[jschwartz]

The 5 speed G50/50 and 52 Turbo boxes are becoming harder to find here in the States.
So we've been providing the GT2 6 speeds, (it has the larger ring gear like those above) again with the taller 1st gear.
Stock 6th in these is .6 something.
Jeff s

Edited by jschwartz on Saturday 6th January 04:49