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5/72 xu1 diff ratio change to more user friendly?


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#1 _Drag lc_

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Posted 22 February 2019 - 10:04 PM

Hi,

I’m just looking for any advice on gear sets for people with xu1’s with no less rims ,sprintmasters that get used with the frequent run on the open road.

I’m just thinking of putting a 2:78 lsd in to get the rpm down on the open road.? What’s everyone’s thoughts on this?

I know to deal with the long bolt ,short bolt housing.

Cheers H

#2 RallyRed

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Posted 23 February 2019 - 05:37 AM

Hi mate,

 

I did the 3.08 to 2.78 ratio swap in my LC GTR, as had a 600km trip + a few others on the plan. 205/60/13 and Sprinters.

 

I really like the change it made.

 

Pulls away from a standstill nicely, is heaps queiter in the car at 110km/h ....reckon it's a win all round. Assume XU1 would be similar.

 

Didn't mention economy, because who cares?



#3 _Drag lc_

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Posted 23 February 2019 - 05:42 AM

Yes it is a bit heaven on gas but my thoughts are to be a little kinder to eng.

Cheers for the feed back mate.

#4 S pack

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Posted 23 February 2019 - 06:27 AM

A 2.78:1 in an XU1 with the 2.54:1 1st gear might not be so nice around town. I'm running a 3.08:1 with the XU1 box and 205/60/13's. Standing starts require a fist full of revs or it bogs down something shocking and hill starts are ............ well lets just say I try to avoid stopping when traversing steep inclines. Cruising around town is nice & lazy but below 60kmh finds you slipping it back into 3rd gear . I put the 3.08 diff in for highway work so I am happy to live with all the aforementioned. :)


Edited by S pack, 23 February 2019 - 06:28 AM.


#5 jd lj

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Posted 23 February 2019 - 06:43 AM

It might be good for the hwy but I think that around town the rest of the traffic will leave you behind when you take off from the traffic lights. It really just depends where you'll be doing most of your driving.

#6 _Drag lc_

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Posted 23 February 2019 - 07:49 AM

Hi Dave, from memory mine has 3;08 in it now, ill do some calculations tomorrow as I've got a bit on today and see what the rpm difference will be @100k's yeah ididnt think of the first gear thats a good point. im not worried about getting left behind at the stop light grand prix , but it is a valid point for sure. if you don't mind me asking what sorta cruise speed are all you guys going if u go far in your xu1's? I'm thinking 100 no more than that. cheers

#7 S pack

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Posted 23 February 2019 - 09:23 AM

Hi Dave, from memory mine has 3;08 in it now, ill do some calculations tomorrow as I've got a bit on today and see what the rpm difference will be @100k's yeah ididnt think of the first gear thats a good point. im not worried about getting left behind at the stop light grand prix , but it is a valid point for sure. if you don't mind me asking what sorta cruise speed are all you guys going if u go far in your xu1's? I'm thinking 100 no more than that. cheers

Given the proliferation of speed cameras these days I like to stick to the posted speed limit, give or take a couple of KMH.



#8 claysummers

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Posted 23 February 2019 - 09:37 AM

It’s been said here before but the M22 4 speed is a good fit in front of the 2.78 ratio. I had one in my 186s powered EK sedan with 205 60 13 rears, but a 3.08 diff. 1280kg with me in it so bout same as LJ. Worked well but would have been better with the taller diff. Third gear around town and fourth is effectively an overdrive for the highway.


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#9 MFM

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Posted 23 February 2019 - 07:10 PM

I have been pondering this exact thing since registering my XU1 2 weeks ago. With a 3.36 its sort of difficult to take off in 1st. Feels like a 2.78 in 1st. Bogs down a bit, have to ride the clutch a bit , so would hate to try a hill start and thats with 3.36 so can only imagine a 2.78 around town would be interesting at lights. Today replaced the 3.36 with a 3.55 LSD. Its only a temporary move till I can set up a nice tight reconditioned 3.36 LSD. 3.55 is great off the line but still have to throttle tickle the take offs.



#10 S pack

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Posted 23 February 2019 - 09:06 PM

It might be good for the hwy but I think that around town the rest of the traffic will leave you behind when you take off from the traffic lights. It really just depends where you'll be doing most of your driving.

Not that bad really, once you get moving the traffic that got the jump on you often ends up behind you by the time you hit 60kmh and pop the shifter from 1st straight into 4th. :)


Edited by S pack, 23 February 2019 - 09:07 PM.


#11 Lc69

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Posted 27 February 2019 - 10:12 PM

Anyone with any experience with the 2.78, M21 with a V8?
My tyres are similar diameter to the 205/60r13
I’ve been contemplating the same issue

#12 S pack

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Posted 27 February 2019 - 10:33 PM

Anyone with any experience with the 2.78, M21 with a V8?
My tyres are similar diameter to the 205/60r13
I’ve been contemplating the same issue

Won't be a problem for a 308 V8 in an LC or LJ. I believe the 2.78:1 diff was std issue in the SL/R 5000.


Edited by S pack, 27 February 2019 - 10:34 PM.


#13 caterham2

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Posted 27 February 2019 - 10:50 PM

Just checked my spread sheet. LJ with 2.54 first gear 3.08 diff as I run in mine  7000RPM=97kph

                                                                                      2.78 diff                           7000RPM 107.7  both the above with 1.81 diameter tyre which is 205/60/13.

 

My car has a pretty ferocious cam etc , hill starts can be interesting!


Edited by caterham2, 27 February 2019 - 10:51 PM.


#14 VIXL34s

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Posted 28 February 2019 - 03:32 PM


Won't be a problem for a 308 V8 in an LC or LJ. I believe the 2.78:1 diff was std issue in the SL/R 5000.



#15 VIXL34s

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Posted 28 February 2019 - 03:39 PM

Yep i have couple l34s 2.78. V8s shit in cities good in country, i live in country. I have converted my Hz gts 308 from 3.36 to 2.78 beautiful for cruising. Jeff

Yep i have couple l34s 2.78. V8s shit in cities good in country, i live in country. I have converted my Hz gts 308 from 3.36 to 2.78 beautiful for cruising. Jeff

#16 Lc69

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Posted 02 March 2019 - 09:11 PM

Thanks guys, sounds like I’ll give it a go and see what it’s like

#17 liswar2

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Posted 14 May 2019 - 08:29 AM

I think this is why I can't find a 2.78 LSD theses days as every one else has picked them up,
I'm looking at going from 3.36 to 2.78 behind the 221/186 strocker , with the m21 ,
Thx wazza




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