89 XJS v12 (Marelli) 5 speed swap

Leave well enough alone. I dunno why people grouse about that rope seal, since it almost never has a problem. You might just remove that rear bearing cap, apply a bead of Loctite 518 on the top, and reseal the sides with new RTV.

I only ask as a friend of mines grandad parked an XJ-S 10 years ago , same year as mine because the rope seal was leaking. Otherwise the car is spotless. Just wondering if I should take it off his hands?

Yes! Rope seals are actually quite dependable. They aren’t 100% as good as a modern seal, but they can be close to leak free. Replacing one with another rope seal won’t accomplish much. If a rope seal is leaking, you need to fix any pcv breathing issues, and change oil frequently.

When i bought my 88 a few years ago, it had sat for 7+ years, and oil looked old. There was a leak from rear main seal.

I cleaned/replaced pcv system, changed oil every few months for a year running dyno oil/marvel mystery oil, then switched to synthetic oil. My rear main seal does not leak three years later, as far as i can see.


Rear main looks really good, actually fantastic. The very slight sheen of oil underneath it is really hard to see without the flash on the camera. And I can’t wipe it off with my fingers…

I cleaned nothing before taking this picture, this is what I saw when I pulled the flex plate off.

The usual suspects, the cam cover half moon seals not so good. Need to add a set of John John’s half moons to my project list.

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Side note: The radiator fairy showed up while I was under the car. This is a project for a later day, possibly while I wait for the transmission. However, I


had to crack it open to inspect it. It’s gorgeous, I might just hang it on the wall in the living room instead of putting it in the car.

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Confirmed that Fidenza fly wheel and stock flex plate are the same diameter, although the teeth on the Fidenza are very slightly finer, there are actually two more teeth on the Fidenza vs the


flex plate. Shouldn’t matter.

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Before I forget, quick tip for torque converter/flex plate removal. The bolts are 15 mm head, and are sort of countersunk behind the starter ring gear. There is not enough clearance between the oil pan and the flex plate to get a conventional socket and ratchet in there, and there’s no way to get a box or a open end wrench in there. I knew what I wanted, but it took me a while to find it. It’s called a go through socket, and it has a three-quarter hex on the outside. You can get the socket over the bolt, then you can get on it with an open end wrench and crack it loose. I got the go through socket set at Harbor freight for like $22.


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Can’t you get to them thru the round access hole covered by the black plastic cover? I think you can remove the cover by removing the oil filter.

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Heh. You are correct sir. I did not know that :grimacing: But now that I read it, it seems like I recently heard it. Clearly I forgot. As I was going through it I kept thinking there has to be an easier way.

Medtronic bell housing drops right into place. The bolts will be WAY easier to get to. Rene’ will be happy about that.

One minor mod (so far) involves this nifty cast flex plate cover that also holds the Marelli engine speed sensor. The Medtronic bell is universal for the 5.3 v12, most of which are not Marelli cars. So I will need to mill a relief in the bottom of the bell. The marked material will be removed. The two surfaces indicated by the pen need to mate up. There should still be a thin lip left for the flex plate cover to mate with.




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Now c’mon, PhoenixBob … you’re able to do that kind of work (e.g. r/r a transmission) with the car only that high off the ground? :open_mouth:

Well… it’s pretty high. Same setup I used to drop the rear cage. I wouldn’t really want it any higher unless I had a commercial trans jack for using with a lift. Th400 is a lotta weight up above your head.

The two critical measurements I wanted before ordering the trans were the input shaft length and the distance from the block to the shifter. Input shaft is easy once the bell is temporarily fitted.

Shifter measurement took a bit of shade tree engineering. From under the car the shifter location is not obvious. There is a nice big access plate that will be exposed when I pull the console, but just where the stock auto shifter rests on it is unknown.

So I used a long bar laid across the console to mark the existing shifter location on the shop floor. Then I moved the bar to the floor and hung the plumb bob from the tunnel even with the bar. (The vac line for the ECU runs down the tunnel. Handy to tie stuff to.). Now know pretty close where the stock shifter is up inside the tunnel.

Measured this against the spec for the new trans and concluded the new shifter will be about 1” aft of the current shifter, which is fine. I was worried about it being farther forward and hitting the console.

Will order the clutch, TO bearing and trans tonight. All of those I held off until I knew the exact trans.

Tomorrow will pull the console.

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Would you mind disclosing the exact parts that you are ordering and where it is that you are getting them?

What exactly do you plan to do about the driveshaft? Will you be going aluminum, and how are you going to handle the sizing?

Sure thing!

Parts list for major components - I will periodically update throughout the project:
Trans (from Summit, AP does not seem to sell direct): Tremec Cobra spec T5 5-Speed - American Powertrain
Link to trans at Summit: American Powertrain 1352-000-251 American Powertrain Tremec T-5 Manual Transmissions | Summit Racing
Clutch: RAM Clutches 88760 RAM Premium Replacement Clutch Kits | Summit Racing
Throwout bearing: RAM Clutches 78125 RAM Hydraulic Release Bearings | Summit Racing. Note: See post 134. A Ford-style T5 will require a different input bearing retainer than stock. I used this one: 78352 - Input collar for 78130 - RAM Clutches
Bleeder: RAM Clutches 78510 RAM Remote Bleeder Kits | Summit Racing
Bellhousing http://www.5speeds.com/cart/index.php?route=product/product&product_id=97
Flywheel: JAGUAR 5.3L/5343cc Jaguar V12 Fidanza Flywheels Parts & Accessories | Summit Racing
Clutch master cylinder: https://mossmotors.com/master-cylinder-8

Driveline will be custom. I will go see Debbie at AZ Driveshaft. No affiliation, Dad and I are just very satisfied customers for the last 3 decades. https://azdriveshaft.com/
Before I unbolted the TH400 rear mount I measured the distance from the center of the output shaft to the floor. That will help me set the proper height of the T5 and make sure the output shaft on the trans is parallel with the pinion shaft in the diff. This is the most critical factor for driveline alignment.

Once the height is set I will measure from output shaft to the flange on the pinion. I will go with the “traditional” slip joint at the trans output shaft (vs. stock drive shaft which has slip joint back by the pinion, and a flange at both ends. I am not going to tear into my brand new trans to convert the output shaft :)) The slip joint needs very little travel, this being an IRS setup, but it needs some to allow for suspension flex and trans mount movement, and to get the driveline in and out.

Once I have my numbers I will take the old driveline and have a sit-down with Debbie and see what she wants to do. My #1 requirement is that this thing be smooth and quiet and obviously no vibrations. Will see what she recommends. When it comes to drivelines I DWDS: Do What Debbie Says.

The trans mount will be fabricated. I have a couple of ideas. I’d like to keep the spring mount. Yes, lots of people go with the rubber block type, that can be fine and I may end up there. However, personal experience with the e-Type conversion indicates that the spring is a bit quieter in terms of driveline noise and high frequency vibrations felt thru the shifter. It’s not dramatic, but enough that I lean to the spring mount if possible. There are some interesting hard points and brackets under the car that support the spring mount. I do not think it will be too bad.

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Progress. I think.

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Can someone remind me of how the switches work?
From left to right, we have 1) reverse lights, 2) park/neutral safety, and 3) some thing that is only depressed when in drive. Not in any other gear including R, 1 or 2.

Am I correct about 1 and 2?
What is 3?
Thanks!

Hey Bob, especially because your in Phoenix while you have the console out why not go ahead and remove those useless AC/ Heater tubes and block the holes off. The air just blows to the back seat that no one will ever use. It will also create more air blowing on you up front. I happen to have had two corks laying around for the longest time that I kept in wait for the occasion to remove the console and to my surprise they fit like a charm, but or course you and just use tape if you wanted to. By the way the idea is not mine but came from Kirby’s book

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Pretty sure you’re correct with 1 and 2. #3 could enable cruise control, and also the extra extra fast idle air to speed up idle when A/C is on, but only in drive. All this from memory, of course!

First thought was the AC idle bump, but I think that comes from the AC compressor circuit switch somewhere? Cruise control is a good guess.