Gearbox options and ratios
06 July 2005, 02:15 PM
#1
Gearbox options and ratios
Having broke my gearbox on the weekend I'm am looking at the options. My intention was to have mine re-built using STi 5/6 gearset. Having spoken to a reputable gearbox builder yesterday left me a little confused.
His view was:
- A STi gearset is no stronger than MY99/00 uk
- Rebuilding the box with sti5/6 gearset would result in slightly taller gears (and hence nicer for drags) than MY99/00 (retaining std diffs)
- Would not need an extra gearchange for 1/4mile (in otherwords 4th would be capable of 115-118mph)
- Wouldnt require an extra gearchange on a UK 6 speed either
What I am looking for:
- A box that isnt going to break every 3-6months
- Ratios similar to MY99/00 uk
- 4th gear capable of 115-118mph
- Reasonable cost (cant afford a PPG at the moment)
Would be happy to hear you views on all of the above.
Bob
His view was:
- A STi gearset is no stronger than MY99/00 uk
- Rebuilding the box with sti5/6 gearset would result in slightly taller gears (and hence nicer for drags) than MY99/00 (retaining std diffs)
- Would not need an extra gearchange for 1/4mile (in otherwords 4th would be capable of 115-118mph)
- Wouldnt require an extra gearchange on a UK 6 speed either
What I am looking for:
- A box that isnt going to break every 3-6months
- Ratios similar to MY99/00 uk
- 4th gear capable of 115-118mph
- Reasonable cost (cant afford a PPG at the moment)
Would be happy to hear you views on all of the above.
Bob
06 July 2005, 02:34 PM
#2
06 July 2005, 03:32 PM
#4
Bob, the Sti gear ratios are no longer than the UK ratios.
If you want a strong syncro box with longer ratios you should look towards the 6 speed fitted in the Forrestor Sti.
UK 5 speed gearing should have allowed you to top 130mph before clattering into the limiter in 4th
If you want a strong syncro box with longer ratios you should look towards the 6 speed fitted in the Forrestor Sti.
UK 5 speed gearing should have allowed you to top 130mph before clattering into the limiter in 4th
06 July 2005, 04:11 PM
#6
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id definitely count the 6 speeder out though bob, mainly due to its extra bulk....even if the ratios are exactly the same id say that youd put an extra 0.2-0.4 on your times minimum with the extra weight that it brings...
06 July 2005, 05:28 PM
#7
However, if you ditch the standard front seats and replace them with lightweight buckets *cough* you would more than make up for the additional weight of the 6 speed, plus have the advantage of the extra weight being low down and in the middle of the chassis 
Ratio wise:
UK 5 Speed (3.9:1 ratio diffs):
1st = 3.454
2nd = 1.947
3rd = 1.366
4th = 0.972
5th = 0.738
Sti (4/5door/P1) 5 Speed (4.444 ratio diffs):
1st = 3.166
2nd = 1.882
3rd = 1.296
4th = 0.972
5th = 0.738
UK Sti 6 speed (3.9:1 ratio diffs):
1st = 3.636
2nd = 2.375
3rd = 1.761
4th = 1.346
5th = 0.971
6th = 0.756
JDM Sti 6 Speed (3.9:1 ratio diffs)
1st = 3.636
2nd = 2.375
3rd = 1.761
4th = 1.346
5th = 1.062
6th = 0.842
JDM Forrestor Sti 6 speed (3.9:1 ratio diffs)
1st = 3.636
2nd = 2.235
3rd = 1.521
4th = 1.137
5th = 0.891
6th = 0.707
Ratio wise:
UK 5 Speed (3.9:1 ratio diffs):
1st = 3.454
2nd = 1.947
3rd = 1.366
4th = 0.972
5th = 0.738
Sti (4/5door/P1) 5 Speed (4.444 ratio diffs):
1st = 3.166
2nd = 1.882
3rd = 1.296
4th = 0.972
5th = 0.738
UK Sti 6 speed (3.9:1 ratio diffs):
1st = 3.636
2nd = 2.375
3rd = 1.761
4th = 1.346
5th = 0.971
6th = 0.756
JDM Sti 6 Speed (3.9:1 ratio diffs)
1st = 3.636
2nd = 2.375
3rd = 1.761
4th = 1.346
5th = 1.062
6th = 0.842
JDM Forrestor Sti 6 speed (3.9:1 ratio diffs)
1st = 3.636
2nd = 2.235
3rd = 1.521
4th = 1.137
5th = 0.891
6th = 0.707
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06 July 2005, 06:04 PM
#9
Bugger... I knew you would be asking me that...erm...it requires more info than I've given you...here, have a play with Wallis' spread sheet where I got the figures from in the first place: http://www.wallis2000.co.uk/uploads/ratios.xls
You can play about with diff ratios and tyres sizes with it to see what effect they have...if you have Excell that is
You can play about with diff ratios and tyres sizes with it to see what effect they have...if you have Excell that is
06 July 2005, 06:42 PM
#10
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dont have the figures here for rpm/mph but I would look for a P1 box and rear diff , especially if your looking at sourcing the parts from a breakers that may not be clued up on scoobs. if the stuffs coming off a P1 at least you should know what your getting.
06 July 2005, 08:48 PM
#15
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Bob,
P1 box with a 7,000rpm rev limit you would be looking at 111.3 mph in 4th, the Jap Show at Pod I was very close to the rev limiter in 4th when crossing the line
it would of most likely been a quicker time if I had changed into 5th and back into a decent torque range.
Changing to 4.11:1 diffs would be the best option with a 120.19 mph at 7,000 rpm ratio.
Using your original 3.9:1 diffs you would have 127.26 mph at 7,000 rpm.
P1 box with a 7,000 rpm limit top speed in 5th is only 146.58 mph.
Figures were worked out using ratios posted by Harvey.
Colin.
P1 box with a 7,000rpm rev limit you would be looking at 111.3 mph in 4th, the Jap Show at Pod I was very close to the rev limiter in 4th when crossing the line
it would of most likely been a quicker time if I had changed into 5th and back into a decent torque range.Changing to 4.11:1 diffs would be the best option with a 120.19 mph at 7,000 rpm ratio.
Using your original 3.9:1 diffs you would have 127.26 mph at 7,000 rpm.
P1 box with a 7,000 rpm limit top speed in 5th is only 146.58 mph.
Figures were worked out using ratios posted by Harvey.
Colin.
06 July 2005, 10:01 PM
#16
Originally Posted by Zen Performance
phase 2 STI and STI type RA/R gears are stronger than UK versions due to a different design.
I know the SN view is the STi gearsets are stronger.
Just a little confused as the gearbox is very reputable.
06 July 2005, 11:11 PM
#18
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Originally Posted by Tim W
Nelio, they are, certainly heavy enough to make up the difference in weight between a 5 and 6 speed box!
i thought the weight difference between the 2 boxes was about 65kgs.....ive taken my passenger seat out at least and that only weighs 22kgs....replacing it with say...a 10kg bucket means a weight saving of 12....so even if the drivers one weighs 5kg or so more your only saving about 25-27kgs?
or is the weight of the boxes much closer? if so ill shut up and probably get one
07 July 2005, 12:02 AM
#19
The difference between the 5 and 6 speed 'boxes is 30kg...
Seat wise I'm looking at fitting a pair of seats (as shown in my earlier group buy link) which with runners should weigh about 7kg apiece
Seat wise I'm looking at fitting a pair of seats (as shown in my earlier group buy link) which with runners should weigh about 7kg apiece
07 July 2005, 12:53 PM
#20
Right. Here are some max gear speeds using matching diffs:
UK MY99/00
Maximum Speed per Gear:
1st: 37.3 mph
2nd: 66.1 mph
3rd: 94.3 mph
4th: 132.5 mph
5th: 174.5 mph
STi5/6/P1 with 4.444diffs
Maximum Speed per Gear:
1st: 35.7 mph
2nd: 60.0 mph
3rd: 87.2 mph
4th: 116.2 mph
5th: 153.1 mph
UK STi 6 Speed
Maximum Speed per Gear:
1st: 35.4 mph
2nd: 54.2 mph
3rd: 73.1 mph
4th: 95.7 mph
5th: 132.6 mph
6th: 170.3 mph
JDM STi 6 Speed
Maximum Speed per Gear:
1st: 35.4 mph
2nd: 54.2 mph
3rd: 73.1 mph
4th: 95.7 mph
5th: 121.2 mph
6th: 152.9 mph
STi 5/6/P1 Gearset and std uk diffs (3.9):
Maximum Speed per Gear:
1st: 40.7 mph
2nd: 68.4 mph
3rd: 99.3 mph
4th: 132.5 mph
5th: 174.5 mph
Calculated using DeltaDash on 215/40/17s and 7100RPM limit
UK MY99/00
Maximum Speed per Gear:
1st: 37.3 mph
2nd: 66.1 mph
3rd: 94.3 mph
4th: 132.5 mph
5th: 174.5 mph
STi5/6/P1 with 4.444diffs
Maximum Speed per Gear:
1st: 35.7 mph
2nd: 60.0 mph
3rd: 87.2 mph
4th: 116.2 mph
5th: 153.1 mph
UK STi 6 Speed
Maximum Speed per Gear:
1st: 35.4 mph
2nd: 54.2 mph
3rd: 73.1 mph
4th: 95.7 mph
5th: 132.6 mph
6th: 170.3 mph
JDM STi 6 Speed
Maximum Speed per Gear:
1st: 35.4 mph
2nd: 54.2 mph
3rd: 73.1 mph
4th: 95.7 mph
5th: 121.2 mph
6th: 152.9 mph
STi 5/6/P1 Gearset and std uk diffs (3.9):
Maximum Speed per Gear:
1st: 40.7 mph
2nd: 68.4 mph
3rd: 99.3 mph
4th: 132.5 mph
5th: 174.5 mph
Calculated using DeltaDash on 215/40/17s and 7100RPM limit
07 July 2005, 03:04 PM
#23
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The weight difference is only 20kg between the boxes.
I personally have never agreed with the suggestion that the boxes off an STI MY99/00 are stronger than the UK ones, i personally think its purely down to mechanical sympathy. Something, which like me, you appear to lack when it comes to gearboxes.
IMO, based on your times and your apparent ability to drag race your car, your long term solution is a PPG kit for your CURRENT box, either that or start regarding the box as a consumable if your going drag racing as often as you are.
As for not needing an extra gearchange with a 6 speed to do the quarter, rollox, you WILL. (Been there done that on both a JDM and UK)
My 2nd UK MY00 box did more drag runs than my 1st one, and was running well when removed from the car. I happened to put 4.5 litres of oil in that box each time i changed the oil.
If you want my advice, buy a cheap MY00 box, take it easy (ie stop dragging the car) and save for the ppg kit.
Steven
I personally have never agreed with the suggestion that the boxes off an STI MY99/00 are stronger than the UK ones, i personally think its purely down to mechanical sympathy. Something, which like me, you appear to lack when it comes to gearboxes.
IMO, based on your times and your apparent ability to drag race your car, your long term solution is a PPG kit for your CURRENT box, either that or start regarding the box as a consumable if your going drag racing as often as you are.
As for not needing an extra gearchange with a 6 speed to do the quarter, rollox, you WILL. (Been there done that on both a JDM and UK)
My 2nd UK MY00 box did more drag runs than my 1st one, and was running well when removed from the car. I happened to put 4.5 litres of oil in that box each time i changed the oil.
If you want my advice, buy a cheap MY00 box, take it easy (ie stop dragging the car) and save for the ppg kit.
Steven
07 July 2005, 03:46 PM
#24
Thanks Steve. Was my feeling too, that if the MY99/00 gearsets are as strong as STi5/6 gearsets, then it would be worth just treating MY99/00 boxes as consumables. They are cheap enough after all:
1. STi5/6 Gearbox + diff (£500-750)
2. P1 box + diff (£500-750)
2. Have mine rebuilt with STi gearset (£1200)
3. Buy cheap MY99/00 boxes and replace whenever they pop (£150-300)
4. PPG (£3k?)
1. STi5/6 Gearbox + diff (£500-750)
2. P1 box + diff (£500-750)
2. Have mine rebuilt with STi gearset (£1200)
3. Buy cheap MY99/00 boxes and replace whenever they pop (£150-300)
4. PPG (£3k?)
07 July 2005, 03:58 PM
#25
Drag it!
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3. £400-£500 IMO
4. £1895 + build + parts + VAT
I dont know whether you are doing any mechanical work yourself, ie swapping the box, if not add that to the cost, and suddenly the PPG seems attractive.
4. £1895 + build + parts + VAT
I dont know whether you are doing any mechanical work yourself, ie swapping the box, if not add that to the cost, and suddenly the PPG seems attractive.
07 July 2005, 05:07 PM
#27
Speak to Paul at Zen Performance
WRT your calcs with the different diff ratios, you do realise that you would need to fit a different rear crown wheel and pinion if you go for a box that has a 1:1 transfer box (ie any of the JDM Sti/P1 gearboxes). THe stock uk rear is 3.54:1, you would need the cwp from a sport which is 3.9:1
WRT your calcs with the different diff ratios, you do realise that you would need to fit a different rear crown wheel and pinion if you go for a box that has a 1:1 transfer box (ie any of the JDM Sti/P1 gearboxes). THe stock uk rear is 3.54:1, you would need the cwp from a sport which is 3.9:1
07 July 2005, 06:07 PM
#29
Originally Posted by BOB'5
Any idea on total cost of PPG?
straight cut syncro 4 gearset 5th oe £1895+vat
labour £250+vat for fitting gearset
+ any worn parts (not usually required)
Total £2520 inc vat
http://www.ppgearbox.com.au/html/information.htm PPG website mentions dog gearset capable of 600bhp
Last edited by andy97; 07 July 2005 at 06:13 PM.
07 July 2005, 06:09 PM
#30
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the STI gears have a different tooth profile, they use a larger tooth and are definitely larger than the standard UK gears including the my01 new age uk gears I have here in a bad way.