I was just wonderin whats the prefferd diff for racing around the streets?Got a celica 5spd
currently got 3.55 which is great for launching and 2nd gear,but on the freeways revs out and uselss
Was thinking of 3.36?? BOC LOCKER?
Best all round street diff ?202
Started by
_troy_
, Oct 26 2006 11:04 PM
18 replies to this topic
#2
Heath
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Posted 27 October 2006 - 10:53 AM
3.36 is a good all-around ratio and with the five speed you'll still maintain pretty reasonable rpm at 60MPH
BOC LOCKER? Not following...
BOC LOCKER? Not following...
#3
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Posted 27 October 2006 - 10:59 AM
BOC locker i think means welding the diff into a locker. BOC the welding gear mob
#4
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Posted 27 October 2006 - 01:52 PM
You can calculate the effect of changing diff ratios by using the following formulae.
Change = ( 1 - ( CurrentDiff / NewDiff ) ) * 100
If the RPM is 3000 for 100 KM/H with a 3.55 then it would change by ( 1 - ( 3.55 / 3.36 ) ) * 100 = -5.6% or 3000 * 5.6 / 100 = 168 RPM to 2832 RPM for a 3.36.
If the RPM is 3000 for 100 KM/H with a 3.55 then it would change by ( 1 - ( 3.55 / 3.08 ) ) * 100 = 15.2% or 3000 * 15.2 / 100 = 456 RPM to 2544 RPM for a 3.08.
When choosing a diff ratio it is important to know what the top gear ratio of your gear box will be. For example the diff you would choose for a TH350 will be different to the diff you would choose for a TH700 because the TH350 has a top gear ratio of 1:1 whereas a TH700 has a top gear ratio of 0.7:1.
Tyre choice can also have a significant impact on the diff ratio choice. Going from 235/50/13 to 205/65/14 will increase speed by approximately 10%.
To calculate the speed of the car for a given RPM, Gearbox ratio, Diff ratio and tyre you can use the following formulae.
KM/H = EngineRPM / GearboxRatio / DiffRatio * TyreCircumference * 6 / 10000
For example.
Top gear in a non-overdrive gearbox is 1:1
A Toyo 235/40/17 has a circumference of 1.88m
Diff ratio 3.55:1
KM/H = 3000 / 1 / 3.55 * 1.88 * 6 / 100
KM/H = 95
Diff ratio 2.78
KM/H = 3000 / 1 / 2.78 * 1.88 * 6 / 100
KM/H = 121
Change = ( 1 - ( CurrentDiff / NewDiff ) ) * 100
If the RPM is 3000 for 100 KM/H with a 3.55 then it would change by ( 1 - ( 3.55 / 3.36 ) ) * 100 = -5.6% or 3000 * 5.6 / 100 = 168 RPM to 2832 RPM for a 3.36.
If the RPM is 3000 for 100 KM/H with a 3.55 then it would change by ( 1 - ( 3.55 / 3.08 ) ) * 100 = 15.2% or 3000 * 15.2 / 100 = 456 RPM to 2544 RPM for a 3.08.
When choosing a diff ratio it is important to know what the top gear ratio of your gear box will be. For example the diff you would choose for a TH350 will be different to the diff you would choose for a TH700 because the TH350 has a top gear ratio of 1:1 whereas a TH700 has a top gear ratio of 0.7:1.
Tyre choice can also have a significant impact on the diff ratio choice. Going from 235/50/13 to 205/65/14 will increase speed by approximately 10%.
To calculate the speed of the car for a given RPM, Gearbox ratio, Diff ratio and tyre you can use the following formulae.
KM/H = EngineRPM / GearboxRatio / DiffRatio * TyreCircumference * 6 / 10000
For example.
Top gear in a non-overdrive gearbox is 1:1
A Toyo 235/40/17 has a circumference of 1.88m
Diff ratio 3.55:1
KM/H = 3000 / 1 / 3.55 * 1.88 * 6 / 100
KM/H = 95
Diff ratio 2.78
KM/H = 3000 / 1 / 2.78 * 1.88 * 6 / 100
KM/H = 121
Edited by AndyCullen, 27 October 2006 - 01:54 PM.
#5
_rorym_
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Posted 27 October 2006 - 06:25 PM
Heres a tip...Dont race around the streets. Save it for a track.
R
R
#6
_keith1962_
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Posted 27 October 2006 - 06:46 PM
Thats right Rory & as for ratio i would
suggest 3.08:1 ratio for a all rounder.
cheers Keith
suggest 3.08:1 ratio for a all rounder.
cheers Keith
#7
_JBird_
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Posted 28 October 2006 - 10:53 AM
"Heres a tip...Dont race around the streets. Save it for a track.I was just wonderin whats the prefferd diff for racing around the streets?
R "
Owned.
It looks like DA has some competition as the resident "numbers" guy from Andy Cullen. Unless they're the same person
#8
Heath
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Posted 28 October 2006 - 11:14 AM
I wouldn't say that's owned at all, I assumed he was using that as a figure of speach. Even if it was literal, giving someone advice isn't owning someone anyway. Owned seems to have lost it's meaning...
#9
RIM-010
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Posted 28 October 2006 - 11:29 AM
I agree. that is in no way owned.
Check this out for ownage - www.jbird.justgotowned.com
RIM
Check this out for ownage - www.jbird.justgotowned.com
RIM
#10
_evilsim_
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Posted 28 October 2006 - 11:38 AM
Agree's with Keith ... unless your motor is gutless then go 3.55.Thats right Rory & as for ratio i would
suggest 3.08:1 ratio for a all rounder.
cheers Keith
#11
_keith1962_
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Posted 28 October 2006 - 12:06 PM
Thats why i run a 3.55:1 ratio diff because its a stocker
cheers Keith
cheers Keith
#12
_JBird_
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Posted 28 October 2006 - 01:00 PM
I retract my previous statement.
I run 3.36 with a pretty stock 202, celica 5spd. Is pretty good, had the 3.08 in before and found not a hell of a lot of difference between the two except for 1st gear. Takes off a fraction quicker. Apart from that 100rpm here and there isn't much. I'd take 3.36 over 3.08 though, can leave it in third and still go up small inclines where the 3.08 would jerk abit
plus you can re-use your short bolts.
I run 3.36 with a pretty stock 202, celica 5spd. Is pretty good, had the 3.08 in before and found not a hell of a lot of difference between the two except for 1st gear. Takes off a fraction quicker. Apart from that 100rpm here and there isn't much. I'd take 3.36 over 3.08 though, can leave it in third and still go up small inclines where the 3.08 would jerk abit
plus you can re-use your short bolts.
Edited by JBird, 28 October 2006 - 01:01 PM.
#13
_troy_
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Posted 28 October 2006 - 01:50 PM
will probably go for the 336 ratio got a pile of spare 3.55bangos ready to be blown,just wonderin how long the 5spd will put up with the punishment,if it blows will go for the supra box,How well do these welded diffs hold up for??or do the axels usually snap first>
#14
_UCV80_
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Posted 28 October 2006 - 02:06 PM
3.08 if u do a bit of highway, limited highway driveing then 3.36
3.36 revs just over 3000rpm at 100, i think thats too high, you either need a 5sp with over drive or use 3.08 gear.
3.36 revs just over 3000rpm at 100, i think thats too high, you either need a 5sp with over drive or use 3.08 gear.
#15
_wraith75_
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Posted 28 October 2006 - 03:00 PM
iv got a 202 with a talkmaster 4 speed and a 2.78 diff with 205/65/13 hankook's at 100k it's rpm is at 2700 and still got some poke left in it there has been work done to the under the bonet . long live the 202 
Edited by wraith75, 28 October 2006 - 03:01 PM.
#16
_Keithy's_UC_
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Posted 28 October 2006 - 03:48 PM
I have experience 3 different diff ratios in a 'same diameter tyre' UC with 6cyl.
3.9:1 - was in my current UC before the 179HP motor went in. Was sitting around 4000rpm at 100km/h - no way again! It went like stink, but was not good to drive above 80km/h.
3.36:1 - the green UC (which i have sold to a mate and it's now registered). It sits at about 3000rpm at 100km/h - not the biggest fan of that ratio without a 5speed box, but still liveable.
3.08:1 - my current ratio in my UC. Sits at about 2500rpm at 100km/h. I cruised to Melbourne and back in this car not less than 1 week ago - 3000rpm at 120km/h and i was indeed cruising at that speed. It leaves the ability to drop to 3rd at 100km/h to overtake in a hurry, or just leave it in 4th and still get some speed under the old girl in no time! I remember seeing 160km/h a couple of times!
My choice for the street is 3.08:1 because it does not sacrifice acceleration or fuel economy (1550rpm @ 60km/h) and you are not forever changing gears regardless of what people say.
Same choice for the highway...
If you have a stocker (i had a stock 202 and 4speed) with 3.08:1 ratio you will find you run a quicker 1/4 time than with 3.36 and 3.9 because you can stretch 1st gear out to a half-decent 75km/h, 2nd to 120km/h and 3rd to about 160km/h. I'm yet to test how fast it'll go in top gear because 180km/h is quick enough for me (with 2000rpm to spare)...
Your choice though mate, and whatever you do, dont weld your diff...
Cheers
Keith
3.9:1 - was in my current UC before the 179HP motor went in. Was sitting around 4000rpm at 100km/h - no way again! It went like stink, but was not good to drive above 80km/h.
3.36:1 - the green UC (which i have sold to a mate and it's now registered). It sits at about 3000rpm at 100km/h - not the biggest fan of that ratio without a 5speed box, but still liveable.
3.08:1 - my current ratio in my UC. Sits at about 2500rpm at 100km/h. I cruised to Melbourne and back in this car not less than 1 week ago - 3000rpm at 120km/h and i was indeed cruising at that speed. It leaves the ability to drop to 3rd at 100km/h to overtake in a hurry, or just leave it in 4th and still get some speed under the old girl in no time! I remember seeing 160km/h a couple of times!
My choice for the street is 3.08:1 because it does not sacrifice acceleration or fuel economy (1550rpm @ 60km/h) and you are not forever changing gears regardless of what people say.
Same choice for the highway...
If you have a stocker (i had a stock 202 and 4speed) with 3.08:1 ratio you will find you run a quicker 1/4 time than with 3.36 and 3.9 because you can stretch 1st gear out to a half-decent 75km/h, 2nd to 120km/h and 3rd to about 160km/h. I'm yet to test how fast it'll go in top gear because 180km/h is quick enough for me (with 2000rpm to spare)...
Your choice though mate, and whatever you do, dont weld your diff...
Cheers
Keith
#17
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Posted 28 October 2006 - 03:52 PM
you sure its a 2.78? haha sounds like a 3.08iv got a 202 with a talkmaster 4 speed and a 2.78 diff with 205/65/13 hankook's at 100k it's rpm is at 2700 and still got some poke left in it there has been work done to the under the bonet . long live the 202
tourque master is the 4cy philopino box hey? final ratio 1:1
#18
_devilsadvocate_
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Posted 28 October 2006 - 05:33 PM
maybe above tyres ^ are 205/60/13?, otherwise numbers 2700rpm/100kmh would be for a 3.08 ratio.
Phillipino box, or correct term being mc6 or torquemaster is a four speed with no overdrive, and was put behind 173s as well.
There's not much value in talking about which diff is best etc unless you are also quoting what size rear tyres you are running.
Phillipino box, or correct term being mc6 or torquemaster is a four speed with no overdrive, and was put behind 173s as well.
There's not much value in talking about which diff is best etc unless you are also quoting what size rear tyres you are running.
Edited by devilsadvocate, 28 October 2006 - 05:41 PM.
#19
_CHOPPER_
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Posted 28 October 2006 - 05:59 PM
My WB van will be having a Blue 202, BW 5 speed and 4.44:1 diff. With the overdrive, it effectively gives it 3.5:1 gearing. First will be nice and low, ideal when there is 1.6 tonne on the towbar and who knows how much in the cargo area.
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