XJ6 & XJ12 Series I, II & III 1968-1992

XJ12- Transmission

 
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Old 11-24-2014, 04:18 AM
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Question XJ12- Transmission

Hi,

Since I pull my engine out. I have the transmission sitting on the floor as well. The transmission was working fine before to take apart the whole car and I've even drove it for few minutes (about 6 months ago). But the car was sitting for more than ten years!!

The question is: Do you know if these kind of transmissions are getting bad? I mean, just in time, for sitting?

My Idea was to change the front and the back seals, change the fluid and, go. What do you thing? Does somebody has experience with theses gearboxes? I'm not...
It's a BW model 12.
Debbie
 
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Old 11-24-2014, 04:41 AM
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Debbie,

The BW12 is a solid unit, and a very close cousin to the FMX from what I have been told.

The 2nd gear band is the weakest from my experience. It ends up a 2 speed.

Sitting does them no good, but usually some fresh fluid, the seals as you suggest, is all they generally need to go on for a very long time. Sadly, any pre storage damage/wear will not be known until its in and driven.

Given you did drive it a small amount before doing the pull out, I reckon it will be fine.

Ours has topped 500000kms and still does what it should. Vac modulator replaced 10years ago, trans leaks, so it runs about 1ltr down from full, and now it only weeps, fine by me.
 
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Old 11-25-2014, 03:52 AM
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Do you know if I can drop the gearbox once the engine is on the car? I wouldn't take the engine out again? I've called to companies to check my transmission... they want to rebuild it and asking for 2600$... out of budget!
Debbie
 
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Old 11-25-2014, 04:48 AM
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In a word, YES.

Not the nicest of tasks, and that cast iron boat anchor is HEAVY.

Based on what you said about $, i would refit it, new fluid, filter (new or wash it out), and do the seals you mentioned firstly, and then drop and refill that fluid a few (4) times in a short time frame, like 3 months. That will increase the concentration of new fluid up into the 80%+ range, and that can ONLY do good for any/all components.

The vac modulator would be a good thing to replace whilst that unit is out, coz that sucker is near impossible to get at it situ, the spring mount fiasco is simply blocking any access.
 
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Old 11-25-2014, 05:29 AM
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Originally Posted by Grant Francis View Post
The vac modulator would be a good thing to replace whilst that unit is out, coz that sucker is near impossible to get at it situ, the spring mount fiasco is simply blocking any access.
Grant,
I replaced my vac modulator (BW12 trans)with the car on the ground simply by reaching under with a spanner. Very easy to get at,unless something on the V12 exhaust gets in the way. Pic was taken later when I serviced the trans with car on stands.

XJ12- Transmission-dsc_8778.jpg

OEM Modulator part No. 12640

Replacement. FVM-7000 (Modulator FMX/Mod 12/ SP2 Ford)

$34

I got my car down from $3000 to $2000 because it was blowing a truckload of white smoke when sitting nose downhill then driving off.
$34 fix. Lucky I came across this problem before with a Fairmont coupe with 351c and FMX

XJ12- Transmission-hardtop-1.jpg

As Grant says, just change tie fluid 3-4 times. It worked on mine, I have done over 10,000 miles since then. No trouble.
 

Last edited by o1xjr; 11-25-2014 at 05:36 AM.
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Old 11-25-2014, 06:42 AM
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Not sure on the S1, but our S2 V12 had the LH strut arm of the triangle trans mount, and that collision plate nightmare, fair and square blocking any access.

I changed it when I had the mount off for a new cotton reel bush very early in the ownership.
 
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Old 11-25-2014, 06:55 AM
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Sound like the S2 V12 has a lot of difference in the set up. That is why I like straight 6's.
Had plenty of V8's , the odd V4's , V6's fwd etc. Straight 6's an 4's (RWD)always preform well enough and make working on so easy.

I know V6's, V8's and V12's have the power and sound, but inline RWD is so easy to work on I keep finding myself back at straight 6's.

The newish Jeep I just got is a V6, APITA compared to the departed straight 6 Jeep.
 
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Old 12-10-2014, 11:53 PM
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Default GM Transmission

Hi,

Yesterday a friend called me. He has a GM Xj12 transmission sitting in his garage. It was mounted in a running car about year and a half ago. I the worse case if i have to rebuild it in US is much easy to find parts.

So, next question. Is it doable? transmission mounts, the shaft, the bell housing,... are they the same or different. Otherwise, I'm going to rebuild mine BW.

Debbbie
 
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Old 12-11-2014, 01:00 AM
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AFAIK the bellhousing bolt pattern is different between the two so you'd need to overcome that issue before even getting into the smaller details.

Cheers
DD
 
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Old 12-11-2014, 01:29 AM
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Thanks Doug,

So forget about it. I'm going to take apart my transmission. I'm very excited! ... my first automatic transmission. I'll post pics
 
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Old 12-11-2014, 01:51 AM
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Originally Posted by Debbiesidera View Post
[...] I'm very excited! ... my first automatic transmission. I'll post pics
Don't worry, Debbie, there are loads of parts but if you carefully lay them out in the order of disassembly (AND don't wait too long before reassembly) all will go well.

Be sure to replace ALL the "rubber" (neoprene) seals.

You'll have Such a feeling of accomplishment when you're finished!
(';')
 
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Old 12-11-2014, 03:49 AM
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Debbie,

The TH400 will bolt up to the engine, no issues.

The V12 crankshaft in the BW12 cars has a small pilot hole for the convertor snout.

The TH400 crankshaft has a HUGE hole for the convertor snout.

Sooooo, crankshaft change is needed to fit TH400 where a BW12 was, this is what caught me years ago. The other way is a simple adaptor sleeve, which is what I did.

Also the gear select quadrant inside the car is spaced differently for the TH400, which has a loooooong pull from P to R.

Many other little things, but they are the biggies I remember. I fitted a s/hand V12 PreHE engine from a TH400 donor car (TH400 blown) into a BW12 car, and that crankshaft thing was the big issue way back then.
 
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