Removing a GKN and fitting BTR
Discussion
Former Dutch TVR dealer did this conversion earlier this year to my car; sorry it's a Griffith.....
My old '95 GKN unit broke down and they adviced me to go NEW; BTR Hydratrak from Sagaris / Tuscan there are some
new old stock units left via Multipart and Racing Green. Not cheap though but i needed to change all my CV joints also (worn).
So a total rebuild from drivetrain had to be done. You have to buy and adjust 2 lower side BTR brackets and buy a new BTR top bracket and you have to adjust the propshaft + new bushes for the brackets + a new speedsensor and adjust the wires from it.
My garage did a great job and the change is noticeable; from 3.31.1 --> 3.46.1 ratio, quicker pick up!!
I have some pictures;
My old '95 GKN unit broke down and they adviced me to go NEW; BTR Hydratrak from Sagaris / Tuscan there are some
new old stock units left via Multipart and Racing Green. Not cheap though but i needed to change all my CV joints also (worn).
So a total rebuild from drivetrain had to be done. You have to buy and adjust 2 lower side BTR brackets and buy a new BTR top bracket and you have to adjust the propshaft + new bushes for the brackets + a new speedsensor and adjust the wires from it.
My garage did a great job and the change is noticeable; from 3.31.1 --> 3.46.1 ratio, quicker pick up!!
I have some pictures;
Edited by MischaV8 on Monday 22 July 14:29
Edited by MischaV8 on Monday 22 July 14:32
db484bhpv8 said:
Did you go for the 3.08 ratio Richard?
I really like the way mine drives now and ive proved that acceleration is barely affected if at all.
Are all the BTR diffs the same fitted to the later cars and the Chimaera/griff. I really like the way mine drives now and ive proved that acceleration is barely affected if at all.
Do all the bits bolt back on ?
I want the 308 for lower rpm on cruise. .
Another reason why I want to swop is there are no available parts for the GKN.
This is a bit old but may be of some use.
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
I have a GKN which I presume will have to go at some point.
What is the general opinion of which Diff is the best?
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
I have a GKN which I presume will have to go at some point.
What is the general opinion of which Diff is the best?
MischaV8 said:
later Chim / Griff BTR's are all the same with 3.46.1 ratio
...unless they came from the factory with the optional 3.2something ratio option installed - as mine did.Worth double-checking before you change - otherwise you may find the difference less than you hoped.
[OT]
I'm looking at getting the diff rebuilt with the 3.46 ratio rather than my 3.2something - can anybody tell me how much difference this will make to the acceleration/"pick-up"..?
I calculate it as about a 6% difference - which could equate to about 15BHP at the wheels if my calculations are correct(?)...
Has anyone changed these ratios - if so, how much difference did you feel it made?
[/OT]
Thanks,
Dom
SILICONEKID343HP said:
So could you get those fabricated again ?did any chassis rails need modifying How much has it lowered the rpm .
Do the drive shaft etc fit .
No chassis mods the rear bracket can be fabricated as there is a pattern but the fronts were made from my old ones,Do the drive shaft etc fit .
I get 90 at 3000rpm and about 2100 ish at 70
db484bhpv8 said:
Discopotatoes said:
Don't attempt it yourself, in the end I needed to have all three brackets fabricated but now it's in it's transformed the car
Did you go for the 3.08 ratio Richard?I really like the way mine drives now and ive proved that acceleration is barely affected if at all.
Discopotatoes said:
Yes it's the 3.08 and like you say it drives lovely, I've also remapped it to a speed density map as the old map was tps based, that too is now on the money, I just need to get some rolling road time to tweek the ignition and I'm there
Is it the crown wheel and pinion which decides the ratio. ?.How am I going to get one fitted ?
Do you need a MAF for speed density.
Edited by SILICONEKID343HP on Tuesday 23 July 13:34
Discopotatoes said:
Yes it's the 3.08 and like you say it drives lovely, I've also remapped it to a speed density map as the old map was tps based, that too is now on the money, I just need to get some rolling road time to tweek the ignition and I'm there
Nice one Richard 
would like to see the old girl at some point 
SILICONEKID343HP said:
Is it the crown wheel and pinion which decides the ratio. ?.
How am I going to get one fitted ?
Daz, yes the "axle" ratio is totally determined by the crown wheel & pinion. How am I going to get one fitted ?
Then the size of tyres/wheels and circumference, then the gear box ratios - they all contribute to your aim of reducing engine revs for the same "speed".
If you haven't already spoken to an axle specialist (from your questions you may not have?) then call these guys and describe what you want fitted?
Here: http://www.readmanracing.co.uk/contact_us.php
To cut a long story very short - IMVHO, Hydratrac diff............
Go 3.08 Standard with one of these - http://quaife.co.uk/shop/products/qdh4m
Trev
SILICONEKID343HP said:
If there are no GKN parts available what is going to happen when they need refurbing. I`m wondering if it`s time for one of the TVR specialists to fabricate a bracket kit .
I have 2 spare working gkn diffs now I've done the conversion, K4TRV is right, you need the 3.08 non hydratrac btr
Ask so speak to Bernie at CTS about diffs
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