Gearbox rebuild

[Curtis Bay]

My car is undergoing a complete rebuild and as part of that I had always anticipated a five speed gearbox conversion. The difficulty I face is that the more research I do the more I conclude that there doesn't seem to be a single 5 speed conversion that is without its problems. For this reason I have decided to stay with my exisitng close ratio four speed box which is original to the car (early 4.2) and to hell with the higher revs this will incur at cruising speed. I can always play around with the diff ratios later.

The box is currently out of the car and I was hoping for recommnedations on somone to rebuild it. It worked fine whilst it was in the car but I want to take the opportunity to get a 100% reliable box.

Any feedback would be appreciated.

[tim wood]

Hi,
i asked the same question a few weeks ago so a recent thread exists.
a few recommendations are noted on this. I am going to use Klassic transmissions but until the work is complete i cannot say how good a job it will be.

i'll follow your replies with interest.

regards

tim

[Heuer]

Harry (E-Type UK) has just installed a 'Driven Man' 5 speed in his demonstrator so why not give him a ring and ask for a drive. I spoke to Harry earlier this week and he is very impressed with it and took it up to CMC for a business meeting. Nick Goldthorp, CMC MD, drove the car and was equally impressed and promptly ordered one. I think Harry has two boxes left from his first delivery batch on the shelf. Certainly worth having a test drive before you commit to restoring the 4 speed.

I have a 5 speed box and a 2.88 diff and I would not go back to a four speed - in fact I drove one the other day and it is amazing what you get used to, the Jaguar box felt prehistoric by comparison. A view confirmed by the owner when he had a go in mine.

[Curtis Bay]

The issue with all T5 derived boxes is their long term reliability. This is because of the way 5th gear is fitted to the main shaft within the tail housing. It seems there are a variety of methods which deliver differing levels of durability but I have concerns.

I note that E-Type Fabs have changed from a billet case to a cast case on their box. Although this uses T5 style internals I am told that 5th gear is securely fitted and cannot work loose along the mainshaft. Does anyone have any experience / knowledge of this new style box in service?

[Heuer]

There has been a reliability problem with some T5 derived boxes but certainly not all. The problem you refer to occurs because the speedo worm can put pressure on the retaining clip which can come loose leaving both the worm and 5th gear to move backwards, which is not good. Most reputable vendors (Medatronics JT5 and Driven Man) supply their boxes with these flaws well and truly put to bed so it is unlikely to be an issue. The JT5 for example has been installed in over a thousand E-Type's and continues to get glowing reports. More info here: http://www.5speeds.com/copycats.html

I speak from experience as my Derek Watson supplied T5 has been out of the car twice because of this problem and we eventually TIG welded the speedo worm in place to make sure it never happened again. The Watjag T5 is no longer available as the vendor was put off by the warranty claims. If I had the chance I would install the Driven Man 5 speed in a heartbeat because whatever you may think, 5th gear is still necessary even with a 2.88 diff if you intend to go touring. If you are confining your driving to the UK and knocking about on a Sunday stick with the Jaguar box.

The ETF billet case 5 speed never reached production because of reliability problems associated with heat. Not sure anyone has tested the new version.

If in doubt, give Harry a shout and drive his demonstrator. Both Angus and I will be doing so shortly.

[Curtis Bay]

The JT5 does appear to be the best of the establshed T5 derived boxes but I understand that Mediatronics are no longer supplying them to our market due to 'difficulties' in the UK.

If the 'Driven Man' box is now as good as you say it may be worth considering. Their website does not give any recent information and still shows a photo of the box with the downward facing spedo drive which seems to be a source of oil leaks on some boxes employing this location.

I have heard that following their appearance (Driven Man) at Silverstone this year business was fairly brisk so there will no doubt be a fair amount of feedback finding its way onto the pages of this forum in due course.

When I spoke to Harry at E-types UK a couple of weeks ago he was just in the process of fitting their box so had no feedback to give. It will be interesting to know how it fits / performs and how the 5th gear / spedo drive issue has been resolved.

[Heuer]

I grabbed this flyer when I saw the box at Silverstone:

[PeterCrespin]

David, I'm not doubting what has happened to your car but I've been corresponding with someone in a position to know, who tells me WatJag are still selling the boxes and this person has no qualms about the design. I've asked for clarification, since his company is currently doing a box for my D-type and on the face of it the respective accounts seem to be mutually irreconcilable....

Watch this space.

[christopher storey]

The flyer is very strong on advertiser's puff and very short on factual content . Where are the gear ratios mentioned ? What are the optional fifth gear ratios ? And I come back again and again to the fundamental question - with standard 3.07 final drive, and cruising ability easily of 100 mph and in practice a good bit more than that, what is wrong with the standard 4 speed box ? I know that David loves his 5 speeder, but in fact how often do we crusie at more than about 90 mph which equates to 3700 rpm on the 3.07 ratio ?

[Curtis Bay]

Having watched this topic surface again and again on this forum it is clear that there is no clear answer. Comparisons between new 5 speed boxes and old worn out 4 speeds don't provide a decent bench mark and, quite naturally, each manufacturer believes thier conversion is the best and can give a host of reasons to support this assertion. I am sure the debate will rage on and I will watch with interest as new products are introduced and assessed.

Back to the original question, given the shortage of some parts now, can anyone recommend (or advise against -if allowed) a good E-type gearbox specialist? I have looked at the other thread on this subject and will follow up with Klassik Transmissions but any other suggestions are most welcome.

[PeterCrespin]

Having watched this topic surface again and again on this forum it is clear that there is no clear answer .

Well you were the one who asked Curtis!

I have looked at the other thread on this subject and will follow up with Klassik Transmissions but any other suggestions are most welcome.

Derek Watson
JD Classics
CMC
Harvington
etc. etc.

Anyone who does Jags or even classic cars can presumably tackle a gearbox as it's fiddly but not rocket science. Yellow pages would be another place. Why not have a go yourself? It's in the manual.

[PeterM]

Curtis I looked at the market and at the time discounted driven man due to cost and ETF due to supply, eventually went to Elite Racing transmissions. they admitted some early problems re speedo drives but also confirmed they had address the issues, The box fitted with some slight fettling and so far so good, I think if you stick with your four speed you may always think what if

[Heuer]

Elite Racing repaired my Watjag T5 on the recommendation of CMC.

[kingzetts]

I have what I think may be a "real" Medatronics JT5 fitted by the previous owner in 2000 (it has "JT5" cast into the tail housing). I stripped it for a check while doing the restoration.

On my box, there is a dedicated snap ring on the tail of the mainshaft purely to retain the 5th gear, then the speedo drive (which is rebated so that it goes over and covers the 5th gear snap ring and so provide positive retention of that snap ring) goes on the shaft and is retained in turn by another snap ring. Judging by David's writeup of his saga with his box, on his box the 5th gear and the speedo drive were both retained by a single snap ring after the speedo drive.

The design of the retaining method on "my" box clearly would be a more costly approach for the maker, but also more reliable (the 5th gear snap ring is a big robust item in a deep machined groove). I guess it is these sort of internal and therefore "invisible" details which may set apart good from less good boxes.

So far I've had no problems and really like the box but then I've only done about 3,000 miles since rebuild, and the PO had only done about 2,000 miles since the box was fitted from what I can work out from old MOTs.

[Curtis Bay]

Thanks for all the feedback - invaluable.

After deliberating the options and discussing this with a lot of the 'industry' experts I have decided to go for a T5 derived box with the fifth gear located as descibed by Kingzetts above. Hope its the right choice......

The engine and box will soon be ready to be installed so I hope it all fits and works as it should.

[pmansson]

I read about this small company in the Feb 2011 issue of Jaguar World.
Their website: www.klassiktrans.co.uk shows exactly what they are doing.
Has nobody used them?

[abowie]

We put a Driven Man box into a Series 1 OTS about 18 months ago. Really not an easy installation, needed a lot of tunnel fettling. Car is still not complete (owner cashflow issues) so can't comment on driveability.
I have just bought a JT5 for my 3.8 OTS. See my comments on recent thread. The body shell has only just got to the painters so I doubt I'll have the box in before July and hope to be driving the car by November. We may however put this box into a 3.8l FHC, the owner of which wants a 5 speed box to go with his engine rebuild.. if so I should have feedback for you in a couple of months.