Diff change t350
Discussion
Hi,
There are 3 ratios that seem to be the norm: 3.43, 3.73 and 3.91. Most of the TVR's seem to have 3.43's (a sticker is on the diff, or you could count the rotations etc). I believe the higher ratio effectively means you get to 60mph for example, quicker, as you don't need to change gear as quick as you would normally do. It also means your RPM is slightly higher when cruising on the motorway (marginally worse fuel economy). I guess a lower ratio means better for cruising and marginally less pickup, because you will have to change gear earlier.
If you are looking to change/refurb yours, then I was advised that http://www.readmanracing.co.uk are the people to talk to
The TVR Racing Teams send their Gearboxes and Diffs to these guys and I believe they are also ex TVR Factory, having had a brief chat with them a few months ago.
Hopefully this has helped in some way. I'm sure others can offer a better assessment, but this hopefully gets you started
Steve
There are 3 ratios that seem to be the norm: 3.43, 3.73 and 3.91. Most of the TVR's seem to have 3.43's (a sticker is on the diff, or you could count the rotations etc). I believe the higher ratio effectively means you get to 60mph for example, quicker, as you don't need to change gear as quick as you would normally do. It also means your RPM is slightly higher when cruising on the motorway (marginally worse fuel economy). I guess a lower ratio means better for cruising and marginally less pickup, because you will have to change gear earlier.
If you are looking to change/refurb yours, then I was advised that http://www.readmanracing.co.uk are the people to talk to
The TVR Racing Teams send their Gearboxes and Diffs to these guys and I believe they are also ex TVR Factory, having had a brief chat with them a few months ago.Hopefully this has helped in some way. I'm sure others can offer a better assessment, but this hopefully gets you started
Steve
I've done this; gone from the standard diff to a 3.73. For me it's been an improvement, but not night 'n' day. Slightly quicker in gear, and a change up seems to drop you into a better spot in the rev range. I think it suits my 3.6, but I'm not so sure it would make the best of the bigger engines (perhaps the CR box would help).
Slightly higher revs when cruising, but not too intrusive - 2500rpm is roughly 60mph.
There is a spreadsheet somewhere on the forum which you can use to see the effect of each of the diffs on speed v revs.
Slightly higher revs when cruising, but not too intrusive - 2500rpm is roughly 60mph.
There is a spreadsheet somewhere on the forum which you can use to see the effect of each of the diffs on speed v revs.
Edited by SteveO... on Friday 10th May 09:37
SteveO... said:
I've done this; gone from the standard diff to a 3.73. For me it's been an improvement, but not night 'n' day. Slightly quicker in gear, and a change up seems to drop you into a better spot in the rev range. I think it suits my 3.6, but I'm not so sure it would make the best of the bigger engines (perhaps the CR box would help).
Slightly higher revs when cruising, but not too intrusive - 2500rpm is roughly 60mph.
There is a spreadsheet somewhere on the forum which you can use to see the effect of each of the diffs on speed v revs.
Hi SteveO,Slightly higher revs when cruising, but not too intrusive - 2500rpm is roughly 60mph.
There is a spreadsheet somewhere on the forum which you can use to see the effect of each of the diffs on speed v revs.
Edited by SteveO... on Friday 10th May 09:37
What route did you go down to replace the Diff? Refurb? Anywhere in particular or just bought a 3.73 and sold your old one?
Steve
SteveO... said:
I've done this; gone from the standard diff to a 3.73. For me it's been an improvement, but not night 'n' day. Slightly quicker in gear, and a change up seems to drop you into a better spot in the rev range. I think it suits my 3.6, but I'm not so sure it would make the best of the bigger engines (perhaps the CR box would help).
Slightly higher revs when cruising, but not too intrusive - 2500rpm is roughly 60mph.
There is a spreadsheet somewhere on the forum which you can use to see the effect of each of the diffs on speed v revs.
http://www.varleyhyd.com/images/sag/gearspeeds.v2....Slightly higher revs when cruising, but not too intrusive - 2500rpm is roughly 60mph.
There is a spreadsheet somewhere on the forum which you can use to see the effect of each of the diffs on speed v revs.
Edited by SteveO... on Friday 10th May 09:37
Here's the spreadsheet, taken from the Sag bible site
). Ant. said:
Targarama said:
I have a 3.91 with a standard 'box. Quite a big difference in driveability.
In what way?
Targarama said:
The Speed Six engine needs revs to perform. With this final drive ratio, in any gear, at any speed the car is slightly higher revving and pulls more quickly. Feels more spritely and requires less downchanges to make progress. Probably not ideal on a track but in real-world driving it makes a difference.
Cheers.....Subject done to death in 05/06
All press cars had 3:73 diff in so the press acceleration times are based on that diff.
This diff is great in 3rd if you re into you tube top gear test puts the yellow press car against a few other things and it wins hands down
your never going to be doing 174mph so driveability and in gear acceleration is the key
most diffs are exchange from John Reid
All press cars had 3:73 diff in so the press acceleration times are based on that diff.
This diff is great in 3rd if you re into you tube top gear test puts the yellow press car against a few other things and it wins hands down
your never going to be doing 174mph so driveability and in gear acceleration is the key
most diffs are exchange from John Reid
Has anyone gone from an early diff M78 to the later diff M80 as in the Tuscan 2 ?
I have a T350 with a M78 3.4 diff and I have found a M80 3.9 diff.
I'm looking to do this shortly and cant find the mounting brackets 2 x front and 1 x rear for later diff.
I've been told by several specialist's you need to change drive shafts and prop shaft as they are different can anyone confirm this.
Also has anyone gone to a 4.1
I have a T350 with a M78 3.4 diff and I have found a M80 3.9 diff.
I'm looking to do this shortly and cant find the mounting brackets 2 x front and 1 x rear for later diff.
I've been told by several specialist's you need to change drive shafts and prop shaft as they are different can anyone confirm this.
Also has anyone gone to a 4.1
M50GRF said:
Has anyone gone from an early diff M78 to the later diff M80 as in the Tuscan 2 ?
I have a T350 with a M78 3.4 diff and I have found a M80 3.9 diff.
I'm looking to do this shortly and cant find the mounting brackets 2 x front and 1 x rear for later diff.
I've been told by several specialist's you need to change drive shafts and prop shaft as they are different can anyone confirm this.
Also has anyone gone to a 4.1
What engine do you have? Why a 4.1? What are you looking to do?I have a T350 with a M78 3.4 diff and I have found a M80 3.9 diff.
I'm looking to do this shortly and cant find the mounting brackets 2 x front and 1 x rear for later diff.
I've been told by several specialist's you need to change drive shafts and prop shaft as they are different can anyone confirm this.
Also has anyone gone to a 4.1
If you are running standard engine a 3.7 would be a good choice as it gives 25 mph per 1000 rpm as opposed to 27 on 3.4 diff. Think a 3.9 gives around 22 mph per 1000 rpm, like driving around in 4 th on a 3.4( hope you are following). I run a 3.7 with a 4.5 power engine and it to low , so going to change back to a 3.4, as the extra power etc will make life easier. Hope you get sorted!
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