Just a quick hello anda few questions
danielosman - 8/3/07 at 10:18 PM
hi im building a rv8 locost, been on here a few days just searching and reading alot of topics ive picked up a mt75 gearbox and a sierra lsd diff
well the whole rear suspension.
theres a few questions, im going to use irs i havent got hold of the diff and drive shafts yet would any one know how wide they are?
also i havent got the book to hand but how wide is the front suspension has any one made there front a bit wider if the rear is wider?
thanks your reading i look forward to some of your replies
Dan
Avoneer - 8/3/07 at 11:12 PM
I think buying the new book would be a very good start.
Pat...
danielosman - 8/3/07 at 11:18 PM
ive got the new book but its in work the only time i get chance to read atm
Simon - 9/3/07 at 12:06 AM
Daniel,
Mine is based on Ron Champion's 2nd ed book (but chassis is +4" width). There are several torsional stiffness improvements that can be made
- see McSorley et al.
I have Chris Gibbs new book, and had would recommend you go this way (MK will be, from what I gather, providing a lot of backup/support, unless you
want to buy a kit, then I'd suggest visits to kitcar shows to see what takes your fancy, and so you can talk to manufacturers.
I've used Sierra rear end and homemade IRS.
Why are you using an MT75, when the LT77 box is readily available (and fits
)
I would strongly (highly emphasized) recommend that you get the lowest Sierra ratio possible (3.14) as the car will be severly undergeared otherwise.
Poor fuel consumption, useless first gear etc etc.
These diffs are getting rare and expensive, so I'm swapping mine for a Jag unit (2.88:1.00, LSD), though you may find it a better idea to go for
a BMW item - depending on ratio.
ATB
Simon
danielosman - 9/3/07 at 07:06 AM
thanks for your reply simon! i was looking at the McSorley +4 chassis last night, ill be building from scratch (im a steel fabricator) i have readily
acces to tolls that i need,
thanks for your input
Dan
wilkingj - 9/3/07 at 08:10 AM
quote:
Originally posted by Simon
Daniel,
Why are you using an MT75, when the LT77 box is readily available (and fits)
I would strongly (highly emphasized) recommend that you get the lowest Sierra ratio possible (3.14) as the car will be severly undergeared otherwise.
Simon
Sorry... but I have to Disagree here.
I have a RV8, and a Sierra 3.62 LSD with a LT77 box. 5th gear ratio is either 0.79 or 0.83 depending on which lt77 box you have. Mine is 0.83, and
with 17" rims, 40% tyres, and 6000rpm the top speed works out at approx 147MPH. Thats far more speen than I will ever drive at.
with a 3.14 box it would be faster still.
Ive done 125+ (off road of course) and it was still accelerating fairly well. That will do for me.
Only 1st gear is undergeared, as you have so much torque and power its a bit useless except for spinning donuts and producing smoke at the traffic
lights
Mine does 2800 rpm at 70mph in 5th gear, an Excellent lazy cruising speed, hence the 25mpg @ 70mph.
I have 235/40/17" tyres. In hindsight, II should have gone to 265/40 with the corresponding rim sizes. I have 205/40x17 on the front with is
adequate.
This is all on a Luego Viento.
MT75 box is 0.83, 0.82, 0.76, depending on which MT75 box you have.
I get 25mpg on a run at 80mph, and quite a lot less round town with plenty of right foot. But thats to be expected.
Granted Ford 3.14 diffs are very expensive and very rare. The 3.38 is a bit less rare, and both command a high price.
Neither are LSD, unless you modify them.
The 4x4 3.62 LSD diff is more common, and you should get one for about £100 ish.
I got the whole back axle for mine for £80 from a scrappy's. I dont think they knew it was LSD. as they assured me it wasnt LSD. However, pre
visit research and help from this list had armed me with the numbers and letters to look for on the tag.
In Hind sight I wish I had forked out on a conversion plate and put in a MT75, or even a Type 9. All the ford boxes are probably not quite as strong
as the LT77. They are much cheaper, and more plentiful.
Finding a good LT77, or one good enough to refurbish is not so easy.
Having said that read up on the serial numbers for LT77's as there are many "TVR" LT77's out there, most are from SD1's.
Again having all the serial number ranges can help with the price.
Both are good boxes, as long as they are in good condition. You have a lot of torque with the V8. Torque will kill a box just as easily as a lot of
power.
Have fun, think twice or more, and cut / buy once
danielosman - 9/3/07 at 10:14 AM
thanks thats given me abit more insight i think i know a place i might be able to get a lt77 box from i was there yesturday looking for a diff
stumbled acroos a bmw lsd to do you know where i can get the serial numbers from thanks
Dan
Simon - 10/3/07 at 12:42 AM
ATB
Simon
danielosman - 10/3/07 at 03:37 PM
im a bit slow here very new to gear ratio's and final drives etc! but im guessin that shows the lower the final drive the better geering both on
the lt77 box?
wilkingj - 10/3/07 at 06:15 PM
Also the Tyre size makes a difference, bigger the circumference, the higher the gearing effect, just from the tyresize.
Not a huge difference, but every little bit has an overall effect, however small.
ie a 17" x 205/40 is a different circumference to a 17" 205/80.
The /80% profile will have a larger circumference and thus alter the gearing, albeit only slightly.
Something that needs to be worked out when calibrating the speedo for the SVA.
Mark Allanson - 10/3/07 at 06:22 PM
This may be of help
Simon - 10/3/07 at 07:08 PM
quote:
Originally posted by danielosman
im a bit slow here very new to gear ratio's and final drives etc! but im guessin that shows the lower the final drive the better geering both on
the lt77 box?
Dan,
The left side shows my gearing with LT77 and Sierra 3.92 diff.
The right is the ratio of the Jag diff - 2.88:1.
ATB
Simon
[Edited on 10/3/07 by Simon]