Hi all,
I have been thinking about changing the diff ratio on my LC 2 door. (Build Thread to come soon)
It has a 186, Trimatic and a 2.78 banjo diff.
As I am not looking to take it on long highway cruises and i’d like it to have a quicker take off, I am thinking of something a bit shorter like a 3.08 or a 3.36. I already have a 3.55 Centre in my shed so am wondering if it’s not too short, whether I should use that instead of buying another Centre.
Any thoughts are welcome
Cheers
HC
Yet another diff ratio question
Started by
_Housecat1977_
, Oct 26 2017 09:26 PM
20 replies to this topic
#2
Bigfella237
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Posted 27 October 2017 - 12:44 AM
G'day Paul,
It would cost you nothing but a gasket and some diff oil to try the 3.55 (providing you can do it yourself of course) so I say go for it!
It will feel like a different car around town, you'll think someone slipped a turbo under the bonnet, but it will be screaming it's lungs out on the highway with 13" wheels.
EDIT: I forgot to mention... before you start, check whether the 2.78 centre in the car has one bolt longer than the rest (at the bottom of the carrier from memory)?
I'm pretty sure the lower ratios are all short bolts so if the above is true, you'll need to source an extra short bolt for the swap?
Edited by Bigfella237, 27 October 2017 - 12:52 AM.
#3
Posted 27 October 2017 - 04:31 AM
^ The 3.08:1 also has the (two) long bolts due to the different shaped housing to clear the larger pinion gear
#4
_Housecat1977_
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Posted 27 October 2017 - 06:50 AM
Thanks guys, my main concern was any differences between the centres. It turns out I have the long bolts so need to source some new ones.
As a small win for me, I actually have a diff that I painted up years ago to get reconditioned that I thought was 2.78 but checking last night, actually is a 3.08 so, I might tear it down and check it out.
My only reservation on using the 3.55 is that it has a lot of surface rust from sitting in a damp corner before I rescued it. Shouldn’t be too much of a problem I guess.
Just checked on the 3.55 and it binds on the crown gear in one spot, I’ll need to do some further investigation.
As a small win for me, I actually have a diff that I painted up years ago to get reconditioned that I thought was 2.78 but checking last night, actually is a 3.08 so, I might tear it down and check it out.
My only reservation on using the 3.55 is that it has a lot of surface rust from sitting in a damp corner before I rescued it. Shouldn’t be too much of a problem I guess.
Just checked on the 3.55 and it binds on the crown gear in one spot, I’ll need to do some further investigation.
Edited by Housecat1977, 27 October 2017 - 06:54 AM.
#5
Bigfella237
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Posted 27 October 2017 - 07:20 AM
Ah sorry... two bolts it is then, it's been a while since I played with the little banjos.
#6
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Posted 27 October 2017 - 07:43 AM
I've actually never run a trimatic before but they generally use 2.78 and 3.08 gears for a reason don't they? Something as short as 3.55 may not work with the trimatic??
#7
_Housecat1977_
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Posted 27 October 2017 - 04:10 PM
So my decision so far is to put the 3.08 diff in and see how that goes as it will be better than the 2.78 with the view to clean up the 3.55 centre and fit it at a later stage and see how it fairs with the Trimatic.
Anyone else know of reasons why the 3.55 wouldn’t be a good fir with my setup?
Anyone else know of reasons why the 3.55 wouldn’t be a good fir with my setup?
#8
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Posted 27 October 2017 - 05:03 PM
My only reservation on using the 3.55 is that it has a lot of surface rust from sitting in a damp corner before I rescued it. Shouldn’t be too much of a problem I guess.
Just checked on the 3.55 and it binds on the crown gear in one spot, I’ll need to do some further investigation.
If the 3.55 diff gears are surface rusted then they are most likely junk by now.
#9
Posted 27 October 2017 - 08:43 PM
^ Nah, diff gears are pretty robust. I've even used gears with light pitting before with no issues. Make sure you clean them up first of course
#10
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Posted 27 October 2017 - 08:54 PM
+1
#11
_Bomber Watson_
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Posted 27 October 2017 - 09:19 PM
Personally I would be trying to graft the 3.55 center in as well.
You will frOcking love it so long as you dont need to do over 80 for more than 5 minutes or so.
My current daily has 4.3 something in the bum and i love it around town.
#12
_Housecat1977_
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Posted 27 October 2017 - 10:20 PM
I gave the 3.55 a brush off of all the dead spiders and webs then a soak with some wd40 and most of the rust has wiped off so isn’t much of a concern. Also it no longer binds and everything seems to run quite smoothly so I think I’ll give the outside a coat of paint and swap it in when I put the other diff in.
While I don’t want to be doin burnouts I also don’t want to be beaten off the line by gran in her Kia either.
While I don’t want to be doin burnouts I also don’t want to be beaten off the line by gran in her Kia either.
#13
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Posted 28 October 2017 - 05:25 PM
3:36 is the best all round ratio for a Torana I have had. And I have had all of them :-)
#14
Lima31
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Posted 29 October 2017 - 02:02 PM
What tyres / driveline did you run with that?Redslur, on 28 Oct 2017 - 15:17, said:
3:36 is the best all round ratio for a Torana I have had. And I have had all of them :-)
#15
Bigfella237
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Posted 29 October 2017 - 02:24 PM
Yep, you definitely need to consider tyre size, for example, there's almost 10% difference in rotations-per-km between a 175/75R13 and a 205/70R14
Edited by Bigfella237, 29 October 2017 - 02:26 PM.
#16
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Posted 29 October 2017 - 06:24 PM
What tyres / driveline did you run with that?
215/45/17 rear tyres. Great on acceleration and also on the highweay. Same rolling diameter as standard 13's.
#17
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Posted 30 October 2017 - 04:49 PM
For an open different centre I found 3.36 or 3.08 best or else first gear was a waste of time. That was with little 185 70 13s.
#18
_Housecat1977_
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Posted 20 November 2017 - 11:13 AM
So I managed to find a 3.36 centre.
My parts list for when I change this over will be
Gaskets for the centre and axels
Oil
Short studs to replace the long bolts of the 3.08 centre.
(edit) Anything I have missed?
Where is the best place to get the studs?
Edited by Housecat1977, 20 November 2017 - 11:14 AM.
#19
_SableMet7/73_
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Posted 20 November 2017 - 01:14 PM
Hi Paul,
I have the 3:08 housing & use 3:36 & 3:08 centers. I've left the "nuts" in the housing & utilise the
long bolts for the 3:08. For the 3:36 you just use a standard drain bolt & copper washer & the other
to the right (drivers side) I use a allen head bolt as normally theres a stud with a smaller nut due to
the carrier making room a little restrictive for a socket. I use a hex bit socket to torque that 1.
Hope the above isnt just confusing, but tried to put a pic up but no-go.
Jono
#20
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Posted 20 November 2017 - 07:29 PM
Agree with Jono. Forget about studs. When fitting a 3.36 diff in a 3.08 housing I used two short hex head bolts. One with two copper washers for the drain plug and the other with a spring washer and flat washer under the head. A little sealant on the thread of this bolt is a good idea too.
#21
_Housecat1977_
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Posted 20 November 2017 - 08:25 PM
That’s just made it much easier, thanks for the advice guys.
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