LS3 and gearbox options

[TimJM]

Quick question for some of the people who have done LS conversions. Looking at the LS3 top RPM is 6,600 so if going for a six speed box do you find you are constantly changing gear and is the .5 6th really very useful? I'm guessing .5 even at lowish RPM is going to be over 80mph.

Here are the numbers I have found (and I accept they could be wrong):
T56 magnum: 1st 2.97, 2nd 2.10, 3rd 1.46, 4th 1.00, 5th 0.74, 6th 0.50

The TKO600 is only 5 speed but would the easier installation (smaller) and the lighter weight make this a more sensible choice? The ratios I found for this box are:
TKO600: 1st 2.87, 2nd 1.89, 3rd 1.28, 4th 1.00, 5th 0.82

The 1st-3rd look more usable in the real world but is a .82 5th too high? For some background this application would be a daily driver, motorways involved and Cerbera based. From my limited knowledge the TKO sounds an easier install too.

What would interest me is people who have these boxes give me their real world view on characteristics and RPM/MPH at cruising speed.

Thanks.

[SteveSPG]

ive had about all of them in various cars

6 speed is very usable, 6th was 0.5, but in a tvr, it IS a big box, and approx 25lb heavier.

6060 shifting is much better than t56 (IMHO)

tko is available in 2 5th ratios, .8x and .6x....the inputs are a little different but swappable without splitting the box

3.45 i think is a tad short for the .8, i would prefer a 3.07, which would be about spot on

friends with the .6x 5th say it is a big jump from 4th to 5th, a real "cruise only" gear, but ive not had personal experience

Id say the best combination all things being considered f(weight, ease of fit, shifter options/cost/ratios)..for a road car...would be ls3/tko/.85/3.07.


on long runs, 6th used all the time, and more often than you'd think around the lanes

hth

[spartridge]

The timing of this post is opportune as I have been considering moving from a .8x to a .6x 5th gear (LS7/TKO600/3.07)

Anyone else done this? What are you running Brummie?

Steve - would be interested to know more of your friends experiences with this if you could possibly put me in touch?

[spartridge]

oh and sorry, in response to the OP I really like the shift of the TKO...feels a little bit slicker than previous T5 but could be imagining this.

In terms of ratios, would say a 3.07 diff is a must...in fact, the ideal for me would be to have something in the late 2s so that all the gears are a bit longer. Unfortunately don't think that's available without going to a new diff...

[SteveSPG]

spartridge said:

The timing of this post is opportune as I have been considering moving from a .8x to a .6x 5th gear (LS7/TKO600/3.07)

Anyone else done this? What are you running Brummie?

Steve - would be interested to know more of your friends experiences with this if you could possibly put me in touch?

lots of the cobra chaps use the TKO...and this is often discussed.

i had a cob rep with a ls2/tko (.85) and a 2.88. rears were 295/55/15. that was really lovely as a road car, gear changes were not required, just used the torque of the engine.

wouldnt set a track car that way, but for road use it was great.

the t56 does give you both .75 and .5, so a 3.45 is fine, but it is a big box!

[TimJM]

Thanks for the replies so far. It seems a tko600 and a 3.07 diff is looking like the most probable solution currently for me. I know a T56 would fit...I think it has been done in a cerb but a TKO seems to give more room.

I suppose if I found 5th too short I could change the ratio to lengthen it in the TKO.

Did you (people who are running LS engines in TVRs) replace or convert the current diff?

[eff eff]

I've got a TKO 600 on an LS3 with a long 5th and a standard diff, it drives well the acceleration in 2nd 3rd and 4th is bonkers and 5th is great for motorway cruising

[TimJM]

eff eff said:

I've got a TKO 600 on an LS3 with a long 5th and a standard diff, it drives well the acceleration in 2nd 3rd and 4th is bonkers and 5th is great for motorway cruising

Is that a 3.45 diff and what is the 5th long option ratio?

[eff eff]

5th is 0.82, the diff is a standard TVR 500 Hydrotrack I don't know what the ratio is I'm sure someone on here will know

[SteveSPG]

stock diff is normally 3.45 on the tvr.

[RichardD]

spartridge said:

The timing of this post is opportune as I have been considering moving from a .8x to a .6x 5th gear (LS7/TKO600/3.07)

Anyone else done this? What are you running Brummie?
...

I think the best way to think of that tall 5th is fitting a 6 speed box and then having 5th gear disappear (as the difference from 4th to 5th is more like two gearchanges, if that makes sense).

Brummmie went the other way, he had a .6x 5th TKO600 but changed to the closer ratios and at the same time went to a 3.08 diff from 3.45.

[Brummmie]

RichardD said:

I think the best way to think of that tall 5th is fitting a 6 speed box and then having 5th gear disappear (as the difference from 4th to 5th is more like two gearchanges, if that makes sense).

Brummmie went the other way, he had a .6x 5th TKO600 but changed to the closer ratios and at the same time went to a 3.08 diff from 3.45.

Yep, he's right, the high 5th was rubbish, way to bigger step.
I can run a 10, and top 200 so it can't be too far out!?

[TimJM]

Brummmie said:

Yep, he's right, the high 5th was rubbish, way to bigger step.
I can run a 10, and top 200 so it can't be too far out!?

Sounds fine!

I presume this is with the 3.08 diff but what ratio is your 5th now then? Is it back to .82 or .64?

I've just found a really interesting page that discusses various diffs with 5th gear tko/diff configs here:
http://www.5speedtransmissions.com/5sp_comparison....

[Brummmie]

TimJM said:

Sounds fine!

I presume this is with the 3.08 diff but what ratio is your 5th now then? Is it back to .82 or .64?

I've just found a really interesting page that discusses various diffs with 5th gear tko/diff configs here:
http://www.5speedtransmissions.com/5sp_comparison....

Yes, 3.08 and .82, the .64 was so crap i swapped it at a cost of nearly £500, at the same time i changed the standard diff ratio, it was a really good change for the better, you have hindsight here to pull from, if you want it!

[RichardD]

TimJM said:

Sounds fine!

I presume this is with the 3.08 diff but what ratio is your 5th now then? Is it back to .82 or .64?

I've just found a really interesting page that discusses various diffs with 5th gear tko/diff configs here:
http://www.5speedtransmissions.com/5sp_comparison....

Paul has the 0.82 5th. This was the ratio for doing more than 200mph. But then he has done a lot tweaking (like getting the best power at the top of the rev range) .

Some in gear max mph numbers for LS3/430 gearing combinations:-

(3.45 diff, close ratio tko600) 50, 76, 113, 145, 173
(3.08 diff, close ratio tko600) 56, 85, 127, 163, 179
(3.45 diff, wide ratio tko600) 50, 76, 113, 145, 184

Approx top gear rpm at 80mph:
3000rpm (cr, 3.45) vs
2700rpm (cr, 3.08) vs
2400rpm (wr, 3.45).

I don't like the massive 4th to 5th jump (in theory), but it seems to work!

I like the taller gearing overall, it seems more balanced (what is the point in having more power in low gears than you can get to the tarmac?), but with a LS3 and 3.08 diff there would be a little less in gear grunt than a good 5.0 RV8 because of the much taller gearing ! Which would seem strange after doing a big conversion...

[spartridge]

Will give you a shout to discuss Brummie.

[Brummmie]

spartridge said:

Will give you a shout to discuss Brummie.

Sure thing, is there a 3.23 or whatever?
This might be a good shout with a close ratio box on a smaller (standard) LS3 than mine?, you REALLY do not want that sh!tty high ratio 5th, it would work even worse with less grunt, i have the T-shirt...

[TimJM]

Brummmie said:

Yes, 3.08 and .82, the .64 was so crap i swapped it at a cost of nearly £500, at the same time i changed the standard diff ratio, it was a really good change for the better, you have hindsight here to pull from, if you want it!

Happy to pull all the hindsight from you guys that have already gone down the LS conversion road.

My current thinking is to stick with the std .82 TKO600 5th and the std TVR 3.45 diff (trying to keep initial costs low) and then once the engine is run in (and hopefully I have a little more cash) go to a 3.08 or similar diff.

[tvrolet]

I have the 0.82 top gear on the TKO600 in the tvrolet. It's a 'natural' change up from 4th and not an overdrive. However, you're not going to be in to the 200mph club with the 0.82 unless you've got big revs. Here are the top speeds for 6500rpm on a TKO600 with the different diff ratios available - based in 18" Dynags and road tyres (888s), so close to what anyone else would get on 18" wheels.

----3.91---3.73---3.45---3.23---3.07
----MPH----MPH----MPH----MPH----MPH
1-----43-----45-----48-----52-----54
2-----65-----68-----74-----79-----83
3-----96----100----109----116----122
4----123----129----139----148----156
5----150----157----170----181----191

I started out with a 3.73 diff and it was fine on the road - and if that was the only place I used the car I would have kept it. But at the local track (Knockhill) I was on the limiter on 2nd and 3rd at two points but not enough time to change up so I swapped to a 3.45. Better at Knockhill but in truth not terribly noticeable on the road. Despite the kudos of a 191 mph potential of a 3.07 diff, I think it would make 2nd,3rd and 4th just a little high for 'spirited driving'. On the 3.45 you've a reasonable opportunity of pulling peak revs in 4th on very short stretches of road or track.

But that was with a 500hp motor. Not far off firing-up the LS7 - that has a few more ponies so perhaps I'll be finding the 3.45 is too short But 3.45 was fine for me on 500hp and a 6500 rev limit.

[RichardD]

tvrolet said:

But that was with a 500hp motor. Not far off firing-up the LS7 - that has a few more ponies so perhaps I'll be finding the 3.45 is too short But 3.45 was fine for me on 500hp and a 6500 rev limit.

Won't the LS7 be a revvier engine than previous (7k redline), so you'll automatically get a similar result to a taller final drive anyway? (Along with a bit more acceleration at the same rpm as before anyway .)