Taller 5th gear...

[s3c chris]

Whilst looking at the Tremec website on a rainy bank holiday monday, I noticed that the new T5 gearboxes have a taller 5th gear ratio of 0.63:1 as opposed to ours which (I think) is 0.8:1.

I just wondered if anyone has gone down this route and if there are any downsides to the conversion?
Also the new boxes appear to have the older style tailhousing as opposed to the S10 type which my car has, do I assume that the S10 is no longer available and that apart from this the box is otherwise a straight swap with the standard TVR one.

I'm sure the cost is astronomical , I'm more curious than anything I suppose!

Thanks again, Chris.

[BoostedChim]

Might be worth having a chat with John Reid. He should be able to advise if it fits or the case needs modifying. I thought about the same for mine but just bought a 3.08 diff instead.

[phazed 11.83]

BoostedChim said:

Might be worth having a chat with John Reid. He should be able to advise if it fits or the case needs modifying. I thought about the same for mine but just bought a 3.08 diff instead.

Where did you source the 3.08 diff?

[BoostedChim]

phazed 11.83 said:

Where did you source the 3.08 diff?

Australia, it only took a couple of weeks to arrive. He supplied a couple of crush washers too.

http://www.ebay.co.uk/itm/182262640586?euid=262a0d...

[macdeb]

What diameter crown wheel?

[macdeb]

That 5th gear ratio would be way too tall IMHO, be like changing up and missing a gear.

Edited by macdeb on Tuesday 30th May 18:38

[SILICONEKID 345HP 12.03]

I have the 3.08 and love it , faster down the straights and a better feel on the road , each gear seems to go for ever .
Motorway driving feels good , about 500 rpm lower at 70 mph so the engine is far more quiet .

The only thing im not sure about is how it would cope on a sprint or track day.

Its just a pity TVR did not choose the 3.23 on all the v8 's.

[phazed 11.83]

Is the 3.23 available?

Daz, didn't you have a new differential from central TVR?

[jesfirth]

SILICONEKID 345HP 12.03 said:

I have the 3.08 and love it , faster down the straights and a better feel on the road , each gear seems to go for ever .
Motorway driving feels good , about 500 rpm lower at 70 mph so the engine is far more quiet .

The only thing im not sure about is how it would cope on a sprint or track day.

Its just a pity TVR did not choose the 3.23 on all the v8 's.

Just FYI I am am looking at a lower ratio of 3.77 for sprinting which will hopefully be quicker..... We shall see

[Richard 858]

jesfirth said:

Just FYI I am am looking at a lower ratio of 3.77 for sprinting which will hopefully be quicker..... We shall see

You don't need to go any bloody quicker!!!!!!!!!!! When are you out to play Jes?

[SILICONEKID 345HP 12.03]

phazed 11.83 said:

Is the 3.23 available?

Daz, didn't you have a new differential from central TVR?

Yes I did not like the 3.45 after having the GKN 33.1

[SILICONEKID 345HP 12.03]

phazed 11.83 said:

Is the 3.23 available?

Daz, didn't you have a new differential from central TVR?

I asked TVR Central but they said no to that question .

The BTR 3.23 were an option when new.
Ive seen a few 3.23 BTR diffs on fleabay and also available from Australia .

Mt 3.08 is the better race crown wheel and pinion , thats what John Read told me .

[SILICONEKID 345HP 12.03]

Richard 858 said:

You don't need to go any bloody quicker!!!!!!!!!!! When are you out to play Jes?

There are plenty of 3.77 s available , I think the later T cars run the 3.77.

[SILICONEKID 345HP 12.03]

SILICONEKID 345HP 12.03 said:

I asked TVR Central but they said no to that question .

The BTR 3.23 was an option when new.
Ive seen a few 3.23 BTR diffs on fleabay and also available from Australia .

Mt 3.08 is the better race crown wheel and pinion , thats what John Read told me .

[SILICONEKID 345HP 12.03]

SILICONEKID 345HP 12.03 said:

I asked TVR Central but they said no to that question .

The BTR 3.23 was an option when new.
Ive seen a few 3.23 BTR diffs on fleabay and also available from Australia .

Mt 3.08 is the better race crown wheel and pinion , thats what John Read told me .

[BoostedChim]

macdeb said:

What diameter crown wheel?

7.75", you need the M78 series. He does also sell the M75 which I think are 7.5"

Peter, he does also sell the 3.23. Or if you don't mind second hand my brother has a 3.23 hes just swapped out for a 3.08.

http://www.ebay.co.uk/itm/BORG-WARNER-DANA-M78-SER...

[ChimpOnGas]

s3c chris said:

Whilst looking at the Tremec website on a rainy bank holiday monday, I noticed that the new T5 gearboxes have a taller 5th gear ratio of 0.63:1 as opposed to ours which (I think) is 0.8:1.

I just wondered if anyone has gone down this route and if there are any downsides to the conversion?
Also the new boxes appear to have the older style tailhousing as opposed to the S10 type which my car has, do I assume that the S10 is no longer available and that apart from this the box is otherwise a straight swap with the standard TVR one.

I'm sure the cost is astronomical , I'm more curious than anything I suppose!

Thanks again, Chris.

The S10 type tail housing was only used on the very last run of Mk3 Chimaeras, everything else got the TVR linkage to bring the gear stick forward so it entered the car in the right position. TVR only used the highest 'Z' spec T5 which has a torque rating of 330ft/lbs based on 100,000 mile usage, and Borg Warner were always conservative with their figures.

In my opinion the gear rations and steps between the ratios chosen by TVR were pretty much perfect, personally I don't think just fitting a taller fifth is necessarily a good idea for this reason as you'll end up with a big step and losing some of that lovely 5th gear flexibility. A better solution would be to fit a taller diff ratio as Daz has but I think you'd need 300+ torques to make this work well.

The ultimate solution would be a Tremec TR-6060 six speed box with the first five ratios being the same as TVR gave us, but with the addition of the double overdrive sixth ratio. Sadly fitting one to the Rover V8 would be a costly exercise or I definitely would have done it myself already, I believe Engineer 1949 is fitting a TR-6060 to his son's supercharged 4.0 litre as they sensibly return the car to a more GT spec.

The Tremec TR-6060 six speed box has a lovely shift but it's physically very big and very weighty too, probably indestructible on the back of a Rover V8 though, even a heavily tuned or blown one. I'd love a Tremec 6060, sadly the cost of the conversion makes it a very expensive and rather impractical proposition which is why I just focused on making my T5 shift nicer by deleting my TVR linkage using the S10 tail housing and fitting a lighter clutch.

Buying a good used Tremec 6060 from the States for reasonable money isn't a problem, so perhaps Engineer 1949 could come up with a Rover V8 conversion kit to make fitting one to a Chimaera a viable proposition?

[s3c chris]

Hi.

Thank you for the replies.
It seems that the larger gap between fourth and fifth would result in a loss of flexibility so maybe not such a good idea.
My car is a year 2000 and does indeed have the S10 tailhousing as standard. In attempt to cure a very slightly noisy bearing, (despite only 27K at the time) the gearbox has been out twice and "rebuilt" by two very well respected specialists.

Although I am admittedly fussy, I know if something feels right or not and on both occasions this box has never felt right after the rebuilds and the change is nowhere as smooth as it was before it was taken apart. It is surprising just how much this can spoil the enjoyment of the car. I think the term rebuild can be misleading as I think on the first occasion only the preload was adjusted and on the second only front and rear bearings got changed along with 3rd gear synchro which always seemed ok. I would expect a rebuild to at least involve new bearings throughout.

Anyway, I am still not entirely happy with the way the box works and the first to second change often involves a degree of baulking and just doesn't feel like it should. The clutch has been changed and the hydraulics bled and deemed ok.

My original question was based on the fact that I am idly wondering about the cost and fitment of a brand new box! The new ones from Tremec that we see advertised, there is one on ebay at the moment, all have the taller top gear and a differnet tailshaft.

Thanks for your comments, any more would be appreciated...

Regards Chris.

[jesfirth]

Richard 858 said:

jesfirth said:

Just FYI I am am looking at a lower ratio of 3.77 for sprinting which will hopefully be quicker..... We shall see

You don't need to go any bloody quicker!!!!!!!!!!! When are you out to play Jes?

Hi Richard. I am making an appearance at silverstone on the 18th. After that I am not sure yet. Hoepfully a couple of others though. Really missing the fun and banter this year.

[SILICONEKID 345HP 12.03]

There is an overdrive available for the T5