bi22le
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| posted on 14/4/16 at 10:16 PM |
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making a custom diff
Im still in the hunt for higher ratio diff. I have found potential what is my best bet but. .
I have a 7" push in non LSD. The new one is 7.5" bolt on non lsd.
Now, is there potential to change the output type? I know my chassis needs to cater for the wider diff. I was also told that they are longer, can this
be confirmed.
I don't want to change my drive shafts or prop. Simple is best for me right now.
Track days ARE the best thing since sliced bread, until I get a supercharger that is!
Please read my ring story:
http://www.locostbuilders.co.uk/forum/13/viewthread.php?tid=139152&page=1
Me doing a sub 56sec lap around Brands Indy. I need a geo set up! http://www.youtube.com/watch?v=EHksfvIGB3I
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hkp57
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| posted on 15/4/16 at 06:13 AM |
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What Ratio do you have now and what are you aiming for?
Fleet
SKC Raptor R - Hayabusa
Toyota C-HR Hybrid Limited Edition
Honda VFR1200 CrossTourer
DCT
Marlin Roadster 1800
Mercedes Vito 116 Sport
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bi22le
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| posted on 15/4/16 at 06:49 AM |
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I have a 3.92 and i want higher. Im looking at a 4.27
Track days ARE the best thing since sliced bread, until I get a supercharger that is!
Please read my ring story:
http://www.locostbuilders.co.uk/forum/13/viewthread.php?tid=139152&page=1
Me doing a sub 56sec lap around Brands Indy. I need a geo set up! http://www.youtube.com/watch?v=EHksfvIGB3I
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wylliezx9r
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| posted on 15/4/16 at 07:25 AM |
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The nose on the 7.5" diff is 10mm longer (not a lot at all). When I changed up to the 7.5" in my car the 10mm difference was catered for
by the prop slider.
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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Doctor Derek Doctors
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| posted on 15/4/16 at 07:37 AM |
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I think you mean a Lower ratio diff. You get lower number of output turns for the one turn of the input shaft. And so the gear ratio of the diff is
Lower. In the same way that 1st gear is a Lower ratio that 5th in your gearbox.
1.6 MX5 differentials are 4.3:1 apparently, it would be a much more involved change but it will give you what you want. Also they do a 4.1:1 &
3.9:1 as well so you would have some choice to change back to Higher ratio if it wasn't what you wanted.
Designer and Supplier of the T89 Designs - Single Seater Locost. Build you own Single Seater Racecar for ~£5k.
Plans and Drawings available, U2U or e-mail for details.
Available Now: The Sports Racer Add-On pack, Build a full bodied Sports Racer for Trackdays, Sprints and Racing.
www.t89.co.uk
www.racecarwings.co.uk
callan@t89.co.uk
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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hkp57
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| posted on 15/4/16 at 08:05 AM |
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The easiest but not the cheapest would be to fit either a 4.1 or a 4.4 CWP to your 7" diff.
Quaife direct or Raceline supply
Fleet
SKC Raptor R - Hayabusa
Toyota C-HR Hybrid Limited Edition
Honda VFR1200 CrossTourer
DCT
Marlin Roadster 1800
Mercedes Vito 116 Sport
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adithorp
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| posted on 15/4/16 at 09:23 AM |
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quote:
Originally posted by Doctor Derek Doctors
I think you mean a Lower ratio diff....
Beat me to it.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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bi22le
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| posted on 15/4/16 at 06:35 PM |
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Still does not answer my question.
Can i take out the bolt flanges and put in my push in ones?
Track days ARE the best thing since sliced bread, until I get a supercharger that is!
Please read my ring story:
http://www.locostbuilders.co.uk/forum/13/viewthread.php?tid=139152&page=1
Me doing a sub 56sec lap around Brands Indy. I need a geo set up! http://www.youtube.com/watch?v=EHksfvIGB3I
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hkp57
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| posted on 16/4/16 at 06:46 AM |
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quote:
Originally posted by bi22le
Still does not answer my question.
Can i take out the bolt flanges and put in my push in ones?
In basic terms yes you can, take the back cover off and pull out the circlip and pull the drive flanges.
A Great Source of information is here
http://www.super7thheaven.co.uk/blog/differentials/sierra-rear-differential/
Part 16 is your Circlip.
I would guess your problem would be the 7.5" and 7" diffs have different shaft lengths and different splines.
I have not worked on a 7.5" so i am basing this on paper information.
[Edited on 16/4/16 by hkp57]
Fleet
SKC Raptor R - Hayabusa
Toyota C-HR Hybrid Limited Edition
Honda VFR1200 CrossTourer
DCT
Marlin Roadster 1800
Mercedes Vito 116 Sport
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bi22le
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| posted on 16/4/16 at 09:17 AM |
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Hmm. So its seems to me that i cant change the bolt on for push in half shafts, the nose of the diff so to long and its not going to bolt easily in to
my chassis.
Boo
Track days ARE the best thing since sliced bread, until I get a supercharger that is!
Please read my ring story:
http://www.locostbuilders.co.uk/forum/13/viewthread.php?tid=139152&page=1
Me doing a sub 56sec lap around Brands Indy. I need a geo set up! http://www.youtube.com/watch?v=EHksfvIGB3I
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Flat Pack
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| posted on 16/4/16 at 12:42 PM |
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I had this same problem a few years ago and couldn't find a good solution for the diff I'm afraid.
I broke the 3rd gear synchro on my standard type-9 box and was looking at ways to sort out the gear ratios at the same time as replacing it.
One option was a bgh box and shorter diff to bring the overall gearing down. In theory custom 4.4 and 4.7 cwps exist for the 7" diff, but
they're expensive and nobody actually seemed to have one or know when they might be able to get one.
In the end I left the 3.92 diff and fitted a Caterham 6 speed box instead. 6th is a 1:1 ratio, same as your 4th. It's not cheap and it's
an engine out job, but I couldn't find a practical alternative at the time. It did completely transform the car though, the ratios are spot on
now - it's definitely worth sorting out one way or another.
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bi22le
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| posted on 16/4/16 at 04:13 PM |
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I would of thought it would of been cheaper to fit the 4.27 diff and change all three drive shafts!
You do get obvious other benefits from fitting the 6 speed if your pockets are deep enough.
What engine do you have in your striker?
Track days ARE the best thing since sliced bread, until I get a supercharger that is!
Please read my ring story:
http://www.locostbuilders.co.uk/forum/13/viewthread.php?tid=139152&page=1
Me doing a sub 56sec lap around Brands Indy. I need a geo set up! http://www.youtube.com/watch?v=EHksfvIGB3I
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Flat Pack
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| posted on 16/4/16 at 10:29 PM |
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It's a 20v Silvertop 4AGE in my car. Rev limit is 8000 rpm and it develops most of its power at the top end of the rev range. It was geared
for 170 odd mph in 5th before I changed it and about 140 in 6th now.
My gearbox was broken so I had to change it anyway and the cost of a bgh box and aftermarket diff ratio to make the ratios right was about the same as
the Caterham box and bits and pieces to do the conversion. If you've got a close ratio box already then the diff will be much cheaper (if
they're available) and should work well. I'm not sure a normal type-9 will work as well with the shorter diff though.
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bi22le
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| posted on 17/4/16 at 12:25 PM |
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Nice work, cheers for the info.
I have a 20v blacktop in mine with a 8250 limit and it sings!!
As you know these, even with the VVT, have quite a narrow power band. I only use 5th on in and out laps so anything the wrong side of 1:1 is no good.
The scorpio 4.27 seems a lot of work to get in. I would rather go for a more modern lighter diff that is cheaper and gives the same ratio.
More to think about i guess.
Track days ARE the best thing since sliced bread, until I get a supercharger that is!
Please read my ring story:
http://www.locostbuilders.co.uk/forum/13/viewthread.php?tid=139152&page=1
Me doing a sub 56sec lap around Brands Indy. I need a geo set up! http://www.youtube.com/watch?v=EHksfvIGB3I
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Flat Pack
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| posted on 18/4/16 at 05:11 PM |
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Yes you definitely need to keep them revving to make them work 
I found the rev drop between 2nd and 3rd the most frustrating thing before I changed the box - I'd be trying to use every possible rev in 2nd
(to the point I'd frequently hit the limiter) to try and get somewhere near the power band in 3rd.
Be interested to see what you come up with, something from a Subaru Impreza / Legacy might be an option too if you're going to be changing
mounts, driveshafts etc.
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Rob Allison
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| posted on 19/4/16 at 07:47 AM |
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quote:
Originally posted by bi22le
Im still in the hunt for higher ratio diff. I have found potential what is my best bet but. .
I have a 7" push in non LSD. The new one is 7.5" bolt on non lsd.
Now, is there potential to change the output type? I know my chassis needs to cater for the wider diff. I was also told that they are longer, can this
be confirmed.
I don't want to change my drive shafts or prop. Simple is best for me right now.
I assume this is a frod diff your on about?
The 7" internal parts, including output drive flanges or push in shafts are not interchangable with the 7 1/2". but you can make up a
hydrid drive shaft to use the inner lobo joint on a tripod type push in shaft. Its not easy to find the parts though. You need to measure the spline
size at the shaft end that the cv joint mounts on to. Then find a matching cv joint in the bolt on type.
I'm not sure which parts though. Its been covered on the sierra owner forum before.
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