Hi all,
As i am about to buy a Reco'd Banjo to replace the very tired one in my car at present and would like to double check the ratio before i buy. I read on that holdenpedia at oldholden.com that it would most likely be 3.55:1 ratio.
Could some one confirm this or tell me where to find it as my car was built before it noted the driveline on the tags. The details of my car are as follows;
1972 LJ 4dr SL Sedan, Brisbane built in May '72,
173 with Tri Matic.
Cheers,
Mick
What Diff Ratio in my LJ
Started by
LOWS2
, May 03 2006 09:12 AM
20 replies to this topic
#1
LOWS2
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Posted 03 May 2006 - 09:12 AM
#2
_Flamenco_
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Posted 03 May 2006 - 09:54 AM
I woud've thought it would be a bit taller ratio than that (My 161 and trimatic LC had a 2.78 ratio). Check the metal ring on your diff (around the pinion before it goes inside the banjo housing), there will be the ratio stamped into that but you might have to get a torch and clean the grime off to see it...
#3
makka
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Posted 03 May 2006 - 02:25 PM
if its standard it will either be 2.78 or 3.08.
try and get either 3.08 or 3.36 on your reco diff.
try and get either 3.08 or 3.36 on your reco diff.
#4
gtrboyy
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Posted 03 May 2006 - 03:45 PM
Not really a sure-fire method but the the plate over the bearing seal/under the yoke,if you clean it you should be able to read the numbers stamped on it telling you the ratio.This method only works if the gears are the original for that housing.The sure-fire method is to count the gears.
#5
_gtr161s_
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Posted 03 May 2006 - 10:30 PM
Like everyone else has said , check the flange plate/ring behind the yoke and it will have the ratio stamped on it.
Depending on what you do with your car ie highway cruising, short trips, racing etc or whether its auto or manual, gernerally i think the 3:08 is good allround diff ratio.
Depending on what you do with your car ie highway cruising, short trips, racing etc or whether its auto or manual, gernerally i think the 3:08 is good allround diff ratio.
#6
LOWS2
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Posted 04 May 2006 - 08:37 AM
Cheers guys for the replies, i think i will be going with the 3.08:1 
as i thought the 3.55:1 sounded wrong.
Mick
as i thought the 3.55:1 sounded wrong.Mick
#7
_devilsadvocate_
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Posted 04 May 2006 - 11:02 AM
Double check!
Jack a wheel up.
Have car out of gear with handbrake off.
Put a marker on the tailshaft that you can see, piece of tape or similar.
Rotate the wheel exactly 10 times....counting how many rotations of the tailshaft you see.
Divide tailshaft rotations by 10
ie if you rotate the wheel 10 times and count 31 rotations of the tailshaft:
31/10 = 3.1 .....would be a 3.08.
Jack a wheel up.
Have car out of gear with handbrake off.
Put a marker on the tailshaft that you can see, piece of tape or similar.
Rotate the wheel exactly 10 times....counting how many rotations of the tailshaft you see.
Divide tailshaft rotations by 10
ie if you rotate the wheel 10 times and count 31 rotations of the tailshaft:
31/10 = 3.1 .....would be a 3.08.
#8
gtrboyy
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Posted 04 May 2006 - 04:25 PM
I would put 3.36 ratio,they suited the std & mild sixes that I had & were a good compromise between street driving & a little bit of highway driving.The 3.55 & 3.90 are too short for everday driving & work much better on engines with a lot of work,like the solid cammed/triple webbered engine I used to have in my lc.
#9
LOWS2
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Posted 04 May 2006 - 05:00 PM
Okay guys its either gonna be the 3.08 or 3.36 ratio. I really dont want to get the wrong ratio as its a fair chunk of $$$ for me to spend. Ive listed the driving conditions i encounter daily & mods to car to help with any suggestions you may have.
It is a 4 dr, Auto, 173 with Extractors & Exhaust (possibly a 350 holley soon). I drive mainly to work on 60km/h roads and then highway (90km/h) for 10min to & from work and when i cruise down to Wollongong on weekends.
What would suit me best ??
Cheers,
Mick
It is a 4 dr, Auto, 173 with Extractors & Exhaust (possibly a 350 holley soon). I drive mainly to work on 60km/h roads and then highway (90km/h) for 10min to & from work and when i cruise down to Wollongong on weekends.
What would suit me best ??
Cheers,
Mick
#11
_devilsadvocate_
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Posted 04 May 2006 - 07:42 PM
Have you figured out what youve got now, does it suit at present, or do you feel its revving too hard on the highway etc.Okay guys its either gonna be the 3.08 or 3.36 ratio. I really dont want to get the wrong ratio as its a fair chunk of $$$ for me to spend.
Mick
What size tyre? an important factor too.
#12
_73LJWhiteSL_
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Posted 04 May 2006 - 08:17 PM
If it is a factory Auto, it should have a 2.78 diff in it. Both my car and my parts car were factory autos and both have (had) 2.78s in them.
If its just around town I would go with the 3.36 cause it will give you easier driveablitity and better launch. I smoked the LJ up (stock 173, M20 with extrators and 2 1/4"exhaust) on the first hill start i did after going from 2.78 to 3.36
If you do some highway miles i would go with a 3.08
If you are running 205/60R13 in theory your RPMs at 100KPH with each diff centre will be as follows.
2.78 ~ 2500RPM @ 100KPH
3.08 ~ 2700RPM @ 100KPH
3.36 ~ 3100RPM @ 100KPH
3.55 ~ 3300RPM @ 100KPH
I can tell you the 2.78 and 3.36 are pretty much spot as my Torana did about 2500 RPM @ 100KPH with the old 2.78 With the 3.36 i am running now it does around 3100RPM @ 100KPH which isn't great, its a bit tiring after a long drive.
Steve
If its just around town I would go with the 3.36 cause it will give you easier driveablitity and better launch. I smoked the LJ up (stock 173, M20 with extrators and 2 1/4"exhaust) on the first hill start i did after going from 2.78 to 3.36
If you do some highway miles i would go with a 3.08
If you are running 205/60R13 in theory your RPMs at 100KPH with each diff centre will be as follows.
2.78 ~ 2500RPM @ 100KPH
3.08 ~ 2700RPM @ 100KPH
3.36 ~ 3100RPM @ 100KPH
3.55 ~ 3300RPM @ 100KPH
I can tell you the 2.78 and 3.36 are pretty much spot as my Torana did about 2500 RPM @ 100KPH with the old 2.78 With the 3.36 i am running now it does around 3100RPM @ 100KPH which isn't great, its a bit tiring after a long drive.
Steve
#13
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Posted 04 May 2006 - 09:58 PM
steve: you mentioned the 3.36 giving better launch, is there a big difference between the 3.36 and 3.08 in terms of launch and getting of the line? becuase it seems to have a nice rev zone at 100KPH, so if it had a decent launch it would be ideal
#14
_73LJWhiteSL_
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Posted 04 May 2006 - 10:27 PM
I've never run a 3.08 so i have no idea how it would compare to a 2.78 or 3.36. Basically the 2.78 was very boggy (like an out of tune car) and the 3.36 spins the wheels in the dry in first fairly easily. Believe it or not but going from a 2 1/4" exhaust to 2" exhaust made a lot of difference to how easily it spins the wheels in first in the dry (more torque i would say)
Having said that i am just running a stock 173. If i had a mild anything or a stock 202 i would be running a 3.08 I assume it would give much better cruising at 100KPH.
Steve
Having said that i am just running a stock 173. If i had a mild anything or a stock 202 i would be running a 3.08 I assume it would give much better cruising at 100KPH.
Steve
#15
_devilsadvocate_
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Posted 05 May 2006 - 05:27 AM
In theory?........If you are running 205/60R13 in theory your RPMs at 100KPH with each diff centre will be as follows.
2.78 ~ 2500RPM @ 100KPH
3.08 ~ 2700RPM @ 100KPH
3.36 ~ 3100RPM @ 100KPH
3.55 ~ 3300RPM @ 100KPH
3.08 = 2836rpm/100kmh/205-60-13
2.78 = 2560rpm....
other 2 are 'about right'
But that's for a manual transmission......not sure that the torque convertor in a trimatic is supposed to lock up at 100kmh, perhaps 2-3% slip.
Edited by devilsadvocate, 05 May 2006 - 05:40 AM.
#16
LOWS2
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Posted 05 May 2006 - 09:46 AM
Alright guys i have made an executive decision...i will be putting in a 3.08 ratio. I think it will suit my needs best (launch, drivablity, etc), if i go the 3.36 i think it will be reving too hard on the highway. I will check what i have in her now just to be sure as well.
Thanks for all your help and suggestions guys
, when she goes in on the 17th i will let you know how she goes when i pick her up.
Cheers,
Mick
Thanks for all your help and suggestions guys
, when she goes in on the 17th i will let you know how she goes when i pick her up.Cheers,
Mick
#17
_73LJWhiteSL_
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Posted 05 May 2006 - 10:47 PM
I was expecting someone, mainly you, to comment on this.In theory?........
If you are running 205/60R13 in theory your RPMs at 100KPH with each diff centre will be as follows.
2.78 ~ 2500RPM @ 100KPH
3.08 ~ 2700RPM @ 100KPH
3.36 ~ 3100RPM @ 100KPH
3.55 ~ 3300RPM @ 100KPH
3.08 = 2836rpm/100kmh/205-60-13
2.78 = 2560rpm....
other 2 are 'about right'
But that's for a manual transmission......not sure that the torque convertor in a trimatic is supposed to lock up at 100kmh, perhaps 2-3% slip.
I agree they are not exact, but they are ball park. And 205/60R13s can have different circumference depening on preasure and manufacturer. The only way to get the revs exactly would be by measuring the wheel. And then unless you have a digital tacho, you won't be able to tell anyways.
Yes i did forget to mention manual transmittion, but the the Trimatic has a 1:1 top right?
Glad to see you got your conclusion LOWS2. Hope you are happy with the setup. I am starting to consider a Celica 5 speed with the 3.36
Steve
Edited by 73LJWhiteSL, 05 May 2006 - 10:48 PM.
#18
_devilsadvocate_
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Posted 06 May 2006 - 12:27 AM
What is the point of your response Steve?I was expecting someone, mainly you, to comment on this.�
I agree they are not exact, but they are ball park. And 205/60R13s can have different circumference depening on preasure and manufacturer. The only way to get the revs exactly would be by measuring the wheel. And then unless you have a digital tacho, you won't be able to tell anyways.�
Yes i did forget to mention manual transmittion, but the the Trimatic has a 1:1 top right?
Steve
Why state "in theory" and then complain when someone points out that your figures are as you put it "ballpark"?
You did use the ~sign, but two of your figures were not within the tolerances suggested by your post. ie ~2700RPM would indicate true value anywhere from 2650-2750rpm, whereas the correct value was 2838rpm.
You've been around the forum long enough and have read/contributed to similar threads b4 where Ive posted formulae on how to calculate this figures to a high level of accuracy and a technique to measure your rolling wheel circumference , so I do find it puzzling/annoying that you would claim "in theory", when you have obviously not used any formula to post your figures? If its possible to be accurate, why not be?
Trimatic has a torque convertor, possibly 2-3% slip when warm at 100kmh, but open to suggestions on this.
Edited by devilsadvocate, 06 May 2006 - 12:39 AM.
#19
rodomo
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Posted 06 May 2006 - 01:29 AM
Would I be right to say that "lock up" (within a percentage) would be proportional to throttle position?
If you are changing the axle anyway I would suggest removing the centre as the crownwheel will have the exact "diff ratio" stamped on it regardless of the flange splash sheid and/or tyre size. From there you should be able to choose your replacement. Personally, I'm with Flamenco with the 3.08 for a stocky.
Good Luck!
If you are changing the axle anyway I would suggest removing the centre as the crownwheel will have the exact "diff ratio" stamped on it regardless of the flange splash sheid and/or tyre size. From there you should be able to choose your replacement. Personally, I'm with Flamenco with the 3.08 for a stocky.
Good Luck!
Edited by rodomo, 06 May 2006 - 01:44 AM.
#20
_73LJWhiteSL_
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Posted 06 May 2006 - 01:49 PM
I have worked these figures out in the past, but i couldn't remember them exactly. I wasn't meaning to cause problems but i couldn't remember the exact figures and i didn't have time to sit down work them out at that time. So i typed them up as i remembered them, but i miss remembered the 3.08 post
Please understand devilsadvocate I was not taking a swipe at you for correcting my post, it was ment to be taken in fun, but i do apolige if my post came across in any other way than in the light humor i intended. My point for posting was in humor and not to put you down or your post.
Steve
Please understand devilsadvocate I was not taking a swipe at you for correcting my post, it was ment to be taken in fun, but i do apolige if my post came across in any other way than in the light humor i intended. My point for posting was in humor and not to put you down or your post.
Steve
#21
_devilsadvocate_
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Posted 06 May 2006 - 02:03 PM
Thanks for that ^ Steve, yes I think I did interpret your post as defensive rather than as humour, those little characters doing the pulled faces thing.......possibly sent me the wrong messg.
Anyway, glad we've sorted that out.
Cheers.
Anyway, glad we've sorted that out.
Cheers.
Edited by devilsadvocate, 06 May 2006 - 02:05 PM.
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