I am considering converting my 92 XJS V12 to a Tremec 5sp. manual transmission. Does anyone have experience with this or recommendations?

 

I would suggest caution if going the Tremec 5spd route.
I have an '88 V12 5spd that was originally done using a Tremec T5 world class by the previous owner.
One garage did the conversion and then a second garage had another go at it after issues were encountered.
Three weeks into my ownership the clutch throwout bearing failed prematurely at 6,000 miles.
My mechanic took it apart and found excessive clutch plate wear, but no obvious reason for bearing failure.
Going the tremec route required machining of the bearing to make it fit; not sure if that was a factor or not. Also the output shaft brass bushing was difficult to source I understand.
Rather than replace the clutch and hope for the best, I opted to go with a conversion kit offered by Simply Performance in UK, which uses all off-the shelf components (Getrag was the brand used in the 5spd XJS's). They offered a Getrag 265 5spd conversion kit (~$CAD 4k incl. used gearbox). Luckily I managed to find one locally that was NOS.
I understand that they have officially stopped offering the Getrag conversion kit as used Jaguar-specific gearboxes are increasingly hard to find. However, they are working on doing a kit for the more modern Tremec TKX, which I understand will be available later this year. Ben Thomson at Simply performance was helpful in responding to my questions (ben@simplyperformance..com) Shipping costs from UK may be high!
I am sure there are owners that have made the Tremec T5 work for them, but that was not my experience.

In spite of the anguish and $ bleed, I have to say a 5spd V12 is a thing to behold. I am not sure I would even be an XJS owner if the only option was the 3spd auto (Oh no!, I have just offended 99.86% of forum members!).
Good luck!

Quentin

 

I did a Simply Performance Gertrag swap last year. Excellent people to work with, everything fit. The few issues I did have, Ben took care of promptly. The one thing I'd do different is buy the pedal cluster in the US, as all Simply Performance has is the RHD version. I went thru a lot of fiddling to modify that to fit my LHD car.

From what I've read, a lot of the aftermarket bellhousings for the conversions are not perfectly concentric with the flywheel, and take a lot of fiddling to make them so. The Simply Performance Gertrag mod used a simple adapter plate to use the Gertrag bellhousing. Easy bolt on. They also use the stock Jag throwout bearing arrangement.

The Camp Chaos Chronicles on youtube did a series on converting to a 5 speed. You might want to look at those videos.

There are a lot of other things to consider such as getting driveshaft, electrical mods for cruise control, engine starting, speedometer drive, etc. Also, assuming you have a 2.88 rear end, you'll want to change that. I went with a 3.54.

You may want to talk or email Ben. They may still be able to source a Getrag swap if you are patient.

 

Thank you for your input. It all helps. I have been in touch with Ben Thompson at Simply Performance and he has been extremely helpful. They are no longer offering the Getrag kits because of problems sourcing the gearboxes as well as the pedal boxes. They are in the process of designing a new kit usiing the Tremec 5 sp. He says it may be a few months more before it’s available.
regards,
Tibbetts

 

Tibbets,
I last contacted Ben a month or so ago. He did have a Getrag coming in unexpectedly, and that would have been an option for me, although I was lucky to source one locally, as I said. So that may be a less predictable option from him, pending the availability of the new conversion kit?

I need to check with my mechanic, but I may have a spare pedal box. I think he re-used the one already fitted from the existing conversion, so the one that came from Simply Performance may be available if that helps at all.

Quentin

 

Mozambique,
Thanks again. At this point I am favoring the complete Tremec kit from Moss Motors. They have been Jaguar experts for decades and their product is available.

 

If doing a DIY assembly you should be aware of the bellhousing for the Tremec from 5Speeds as well as the Dellows bellhousings from Au (they've been around for a long time.) ANY bellhousing should be dialed in with a dial indicator and the locator dowels replaced with the proper offset ones to fix any non-concentricity issues.

~Paul K.

 

I recently completed my TKX install, what do you want to know? I used driven man parts, had a few hiccups along the way. Although frustrating at the time, in hindsight I probably over reacted. Nothing is going to be totally plug and play when doing these conversions. Having access to a good machine shop helped me a lot. Also, the reason the Getrags never need alignment is because they are old tech, Tremecs have much tighter tolerances due to modern bearings, you must always check for alignment and use appropriate offset dowels.

 

Did you have any mechanical or fitment issues with the TKX transmission? Also wondering what ratios you chose and how it drives. Thanks

 

Quentin,
Thanks for your input. I have received the left hand drive pedal box so the process has officially begun. Just waiting for final development from Simply Performance.

 

Congratulations!
May the process go as smoothly as a V12!
You won't regret it.
All the best
Quentin

 

i can only speak for the setup I used (quicktime bell housing - as supplied by driven man).

I did not like the way the starter mounted to bell housing. I had machine shop clearance the bell so it could accept bolts oriented as per OEM. Other than that, transmission and bell fit fine. It did require custom machined offset dowels as bell and block were different sizes.

ideally, the transmission could be about an inch more forward as it is pretty close to the opening in the floor. No rubbing though.

i went with a close ratio TKX, this requires 3.54 or higher for best results.

the car is a different beast now, much more enjoyable.

 

I am hearing that people are having fitment issues with the Driven Man bell housing. At this point I am committed to Simply Performance but their kit is still in development. Ben, at Simply Performance has been extremely helpful and has an excellent reputation.

 

Ben is great, i don't think you can go wrong with theirs when its available. I know their focus is always maintaining an OEM type setup which is good. Also, support will be top notch.

I had some hiccups with the DM kit, i worked through them however. It all goes together perfectly in the end. You just need to speak to someone who has done it, DM doesnt really have much support.

 

For what it worth, I drove my V12 with its newly installed Getrag 265 5spd from Simply Performance yesterday for the first time. Significantly improved shift quality compared to the previous T5 5spd installation. Very happy!

 

Thanks Mozambique,
I have received a LHD clutch/brake pedal box and Ben, at Simply Performance, has located a Getrag 265 gearbox for me. He will be shipping it all, air freight, to me this coming week. I am delighted!

 

Oh thats fantastic!
My mechanic installed it and did not report any problems. They had to fabricate a new gearbox mount but that was only because the NOS kit I purchased locally had a mount for a 6 cyl instead of for a 12. The shift to reverse is hard across to the left and up, unusual to me, but not an issue. They had to fuss around a little getting adequate clearance in the transmission tunnel opening to ensure all 5 gears could be selected without obstruction. They just fine tuned the existing opening previously made for the T5, whereas you will be starting from scratch from the existing auto box. I will ask him if he has any tips based on his experiences.

 

Thank you Mozambique,
I anticipate a fairly straight forward installation because of Ben’s support. I do, however, appreciate any input you may have from your experience.
What have you done to your exhaust to enhance your overall driving pleasure?
I just ordered new personalized plates….V12 5SP…😎

 

Comments from my mechanic:

"Depending on what his kit comes with, might need slightly longer bolts for the flywheel as well as new bolts for the starter. The instructions are very good and thorough"

Love the plate No.! I went through every available permutation of XJS, V12 etc., but didn't think of that one. Settled on SILK CAT (TWR Le Mans flavour).
Its crap here in Ontario, its impossible to transfer a personalized plate to anyone else if you no longer need it.

Regarding the exhaust, the previous owner removed baffles from the downpipes and deleted the middle mufflers. Also has a bit more 'throaty TWR style air intakes.

 

Thanks for the tips regarding bolts etc. Ben has told me that he would be available to assist in answering any questions that may arise during the process.
I have removed the small mufflers in the center section but need more exhaust “music”. I have an appointment next week to address that issue.