Gearbox rebuild - ultimate ratios
Discussion
Hi All
I have got to get my gearbox rebuilt after my last track day (it needed it anyway). It's a G50/01 5 speed.
I want to change the ratios to give more relaxed cruising at motorway speeds but still make it usable on the track. As a guide, 3rd and 4th are used most on track. 1st is pretty much useless and I estimate top speed to be about 165/170mph in 5th at about 6600rpm on a tyre with a diameter of 25.45"
I will probably fit a supercharger at some point in the near future so 600 to 650hp will be going through the box so an oil cooler will be fitted too.
The question is :- what ratios should I go for?
You might like to use two types of answer:-
1 Money no object
2 Sensible cost
Dom's gearbox spreadsheet may assist in your suggestions http://redirectingat.com/?id=1044X509854&xs=1&...
I look forward to your suggestions.
Paul
I have got to get my gearbox rebuilt after my last track day (it needed it anyway). It's a G50/01 5 speed.
I want to change the ratios to give more relaxed cruising at motorway speeds but still make it usable on the track. As a guide, 3rd and 4th are used most on track. 1st is pretty much useless and I estimate top speed to be about 165/170mph in 5th at about 6600rpm on a tyre with a diameter of 25.45"
I will probably fit a supercharger at some point in the near future so 600 to 650hp will be going through the box so an oil cooler will be fitted too.
The question is :- what ratios should I go for?
You might like to use two types of answer:-
1 Money no object
2 Sensible cost
Dom's gearbox spreadsheet may assist in your suggestions http://redirectingat.com/?id=1044X509854&xs=1&...
I look forward to your suggestions.
Paul
The basic problems are imo, 1st is too short and 5 the is also too short.
I would fit a huge 1 st gear ie 70mph in that gear or more, i would then fit a big fifth, a G50 52 ratio (.75) would give 210 mph on 335 18's at 7000 rpm, i would then space 2nd, 3rd and 4th equal between 1st and 5th. Can Am Dave has a .65 sixth i believe so i suppose that ratio would be available from CMS?
A Billet side plate is a good investment, billet selecter forks and steel syncros. A LSD would be nice i suppose, CMS do a lovely cable shifter if you want to really invest?
If you plan to blow the LS i would spend a bit on the box to help it cope!! I will send you some details on the blower route if still required, i did plan to blow the LS2 you have and even sorted a custom cam and some steel rods for it. I think the LS2 will work great with a bit of boost 620 will be fairly straight forward but 650 would be possible with a few internal upgrades. We have now got our heads round the GM ecu and superchargers so i think it would be possible to retain that.
I would fit a huge 1 st gear ie 70mph in that gear or more, i would then fit a big fifth, a G50 52 ratio (.75) would give 210 mph on 335 18's at 7000 rpm, i would then space 2nd, 3rd and 4th equal between 1st and 5th. Can Am Dave has a .65 sixth i believe so i suppose that ratio would be available from CMS?
A Billet side plate is a good investment, billet selecter forks and steel syncros. A LSD would be nice i suppose, CMS do a lovely cable shifter if you want to really invest?
If you plan to blow the LS i would spend a bit on the box to help it cope!! I will send you some details on the blower route if still required, i did plan to blow the LS2 you have and even sorted a custom cam and some steel rods for it. I think the LS2 will work great with a bit of boost 620 will be fairly straight forward but 650 would be possible with a few internal upgrades. We have now got our heads round the GM ecu and superchargers so i think it would be possible to retain that.
Hi Kyle
I am planning to get the box up to the spec required for a s/c power output. I hope to use a UK company for the rebuild probably using US/DE parts. It is one of the things I will be looking into at the Autosport Show tomorrow as well as the contacts I already have.
I have already done a simulation on Doms spreadsheet (thanks Dom - its a great spreadsheet) much along the lines of your ratio ideas. I think a 70mph 1st gear might be a bit too much though but fitting the other gears in between a higher 1st and 5th to best use the torque was my thinking too.
With the cost of the box rebuild, the respray and the sundry other parts required for the refurb I think the engine will have to wait for another 6 to 8 months (I've just spent £3.5K on my workshop upgrade too). I would be interested to hear your ideas and any costings you may have though.
Paul
I am planning to get the box up to the spec required for a s/c power output. I hope to use a UK company for the rebuild probably using US/DE parts. It is one of the things I will be looking into at the Autosport Show tomorrow as well as the contacts I already have.
I have already done a simulation on Doms spreadsheet (thanks Dom - its a great spreadsheet) much along the lines of your ratio ideas. I think a 70mph 1st gear might be a bit too much though but fitting the other gears in between a higher 1st and 5th to best use the torque was my thinking too.
With the cost of the box rebuild, the respray and the sundry other parts required for the refurb I think the engine will have to wait for another 6 to 8 months (I've just spent £3.5K on my workshop upgrade too). I would be interested to hear your ideas and any costings you may have though.
Paul
Storer said:
Hi Kyle
I am planning to get the box up to the spec required for a s/c power output. I hope to use a UK company for the rebuild probably using US/DE parts. It is one of the things I will be looking into at the Autosport Show tomorrow as well as the contacts I already have.
I have already done a simulation on Doms spreadsheet (thanks Dom - its a great spreadsheet) much along the lines of your ratio ideas. I think a 70mph 1st gear might be a bit too much though but fitting the other gears in between a higher 1st and 5th to best use the torque was my thinking too.
With the cost of the box rebuild, the respray and the sundry other parts required for the refurb I think the engine will have to wait for another 6 to 8 months (I've just spent £3.5K on my workshop upgrade too). I would be interested to hear your ideas and any costings you may have though.
Paul
No problem PaulI am planning to get the box up to the spec required for a s/c power output. I hope to use a UK company for the rebuild probably using US/DE parts. It is one of the things I will be looking into at the Autosport Show tomorrow as well as the contacts I already have.
I have already done a simulation on Doms spreadsheet (thanks Dom - its a great spreadsheet) much along the lines of your ratio ideas. I think a 70mph 1st gear might be a bit too much though but fitting the other gears in between a higher 1st and 5th to best use the torque was my thinking too.
With the cost of the box rebuild, the respray and the sundry other parts required for the refurb I think the engine will have to wait for another 6 to 8 months (I've just spent £3.5K on my workshop upgrade too). I would be interested to hear your ideas and any costings you may have though.
Paul
I think the little LS2 may need a little refresh after youve given it a hard time for 12 months anyway?
....with V8 torque you need fewer gears..... as already stated big first and tighten the rest up.
I looked at the CWP route too, it will work fine but do the overall reductions for each gear/CWP combo and see what happens.
I think CMS offer a bit of bulk-buy discount if you take a set of gears, maybe more if they do your whole trans.
I looked at the CWP route too, it will work fine but do the overall reductions for each gear/CWP combo and see what happens.
I think CMS offer a bit of bulk-buy discount if you take a set of gears, maybe more if they do your whole trans.
JoulesCanAm said:
Here is what Powerhaus recommended for my G50/52
1st 2.06; 2nd 1.5; 3rd 1.15; 4th 0.85 and 5th 0.68 along with billet side plate, billet shifter forks, steel synchros, LSD, oil spray bar, side shifter etc.
Julian
Julian1st 2.06; 2nd 1.5; 3rd 1.15; 4th 0.85 and 5th 0.68 along with billet side plate, billet shifter forks, steel synchros, LSD, oil spray bar, side shifter etc.
Julian
Edited by JoulesCanAm on Thursday 13th January 05:08
Wow, 70 in 1st at 6500 is a very tall first (10mph at tickover!!!!).
How do you find that in on road driving and parking/pulling away/stop start traffic?
There is also a big jump between 3rd and 4th. Do you do any trackdays and is this too big to be ideal?
Paul
Storer said:
Julian
Wow, 70 in 1st at 6500 is a very tall first (10mph at tickover!!!!).
How do you find that in on road driving and parking/pulling away/stop start traffic?
There is also a big jump between 3rd and 4th. Do you do any trackdays and is this too big to be ideal?
Paul
With the 427 stroker motor I have the rev limiter set at 6,000 to keep maximum piston speed in check, but it's over 500 ft/lb torque so it pulls like a freight train.Wow, 70 in 1st at 6500 is a very tall first (10mph at tickover!!!!).
How do you find that in on road driving and parking/pulling away/stop start traffic?
There is also a big jump between 3rd and 4th. Do you do any trackdays and is this too big to be ideal?
Paul
In traffic it's a b
h, a lot of clutch work, but the car has only covered 2,000 miles since 2004 build and probably 1,800 of those are track miles. It wouldn't do for an everyday commuter.... that's what one of the Pantera's is for 
The 3rd to 4th shift is a 1,500 rpm difference, not a problem behind a torque monster V8 IMO.
Julian
As I mentioned some where else, the problem isn't the gearbox, it's the combination, curbweight,enginetorquecurve and gearboxratio's.
If you look at the total package, the gearbox isn't the problem. The torquecurve of the engine most people are using is wrong.
The gearbox comes from a porsche 911. They have huge amount of development in the gearbox, in combination with THEIR engine. So if you want the ideal combination at least look at the torquecurves of the Porsche engine before you choose the engine for the Ultima.
I have been looking at those figures and I chose to go a total different direction, with a highrev torqueband, similar to the porsche only a lot more. If you take a normal USA enginebuilder, they will deliver you the opposite of what you need for the carweight/G50 combination.
A racecar will always have a very long first, to have smaller ratios between 2nd and 5th or 6th.
For daily roadusage this is impossible use, or accept clutch rebuild every 10000miles.
The engine used by most of the Ultimadrivers still has the same caracteristics of old USA musclecars, so accept this and go for the three speed automatic which belongs to that configuration.
Writing this, makes me realize there is a transaxle gearbox which has exactly what you need..
the Audi diesel!
If you look at the total package, the gearbox isn't the problem. The torquecurve of the engine most people are using is wrong.
The gearbox comes from a porsche 911. They have huge amount of development in the gearbox, in combination with THEIR engine. So if you want the ideal combination at least look at the torquecurves of the Porsche engine before you choose the engine for the Ultima.
I have been looking at those figures and I chose to go a total different direction, with a highrev torqueband, similar to the porsche only a lot more. If you take a normal USA enginebuilder, they will deliver you the opposite of what you need for the carweight/G50 combination.
A racecar will always have a very long first, to have smaller ratios between 2nd and 5th or 6th.
For daily roadusage this is impossible use, or accept clutch rebuild every 10000miles.
The engine used by most of the Ultimadrivers still has the same caracteristics of old USA musclecars, so accept this and go for the three speed automatic which belongs to that configuration.
Writing this, makes me realize there is a transaxle gearbox which has exactly what you need..
the Audi diesel!
Dear Harry,
it is not as bad as you describe, I would say the G50 with standard ratios is a very good fit albeit not perfect. I have installed a longer 5th gear 0,76 which is great for highway cruising and the jump from 4th to 5th is tolerable. The car is doing great in 3rd and fourth which is what you use most of the times on country raods. I thing choosing the right gears and gearbox is very depending what the car is going to be used for. In my case mainly road as I have a smaller version of Nordschleife in front of the house.
I got a AUDI gear box for Grant and it was 1000 EURO new !, not sure if it can take the torque of the LS7 ?
it is not as bad as you describe, I would say the G50 with standard ratios is a very good fit albeit not perfect. I have installed a longer 5th gear 0,76 which is great for highway cruising and the jump from 4th to 5th is tolerable. The car is doing great in 3rd and fourth which is what you use most of the times on country raods. I thing choosing the right gears and gearbox is very depending what the car is going to be used for. In my case mainly road as I have a smaller version of Nordschleife in front of the house.
I got a AUDI gear box for Grant and it was 1000 EURO new !, not sure if it can take the torque of the LS7 ?
spatz said:
Dear Harry,
it is not as bad as you describe, I would say the G50 with standard ratios is a very good fit albeit not perfect. I have installed a longer 5th gear 0,76 which is great for highway cruising and the jump from 4th to 5th is tolerable. The car is doing great in 3rd and fourth which is what you use most of the times on country raods. I thing choosing the right gears and gearbox is very depending what the car is going to be used for. In my case mainly road as I have a smaller version of Nordschleife in front of the house.
I got a AUDI gear box for Grant and it was 1000 EURO new !, not sure if it can take the torque of the LS7 ?
My remark has a cynical undertone, so do not take it 100% serious. If the gearbox comes from a diesel it will be fine for an LS7.it is not as bad as you describe, I would say the G50 with standard ratios is a very good fit albeit not perfect. I have installed a longer 5th gear 0,76 which is great for highway cruising and the jump from 4th to 5th is tolerable. The car is doing great in 3rd and fourth which is what you use most of the times on country raods. I thing choosing the right gears and gearbox is very depending what the car is going to be used for. In my case mainly road as I have a smaller version of Nordschleife in front of the house.
I got a AUDI gear box for Grant and it was 1000 EURO new !, not sure if it can take the torque of the LS7 ?
So if I understand it right, the big question with the choice of the gearbox is, are you (not you) a showoff cruising through town, or a diehard trackday warrior??
Not keen on the audi box... in order to fit an audi I would have to raise my engine 8inches over my porsche unit!
I am using a GT3 race box (and have a GT2 box to steal ratios from if needed) which had fantastic spaced ratios, but a higher than normal final drive making all the gears too low (160mph top speed!) hence fitting a lower final drive is the best solution for me.
The change give me a 230mph top gear and 60mph ish 1st.... my canam had a 4 speed box and a 60mph 1st and 212mph 4th... the only place it wasnt devastatingly fast was above 160mph were it could have done with an extra gear when you changed into 4th!
Worth noting that my canam SBC rev'd past 7,000rpm and I plan my V12 to go beyond 7,500rpm
I am using a GT3 race box (and have a GT2 box to steal ratios from if needed) which had fantastic spaced ratios, but a higher than normal final drive making all the gears too low (160mph top speed!) hence fitting a lower final drive is the best solution for me.
The change give me a 230mph top gear and 60mph ish 1st.... my canam had a 4 speed box and a 60mph 1st and 212mph 4th... the only place it wasnt devastatingly fast was above 160mph were it could have done with an extra gear when you changed into 4th!
Worth noting that my canam SBC rev'd past 7,000rpm and I plan my V12 to go beyond 7,500rpm
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