TH400 Drain Confusion

#1

So I’m slowly doing drain/refills on my 1988 XJS (1987 manufactured TH400) now that I’ve installed a new deep pan with a drain plug.

Everywhere I read, our TH400 w/ deep pan has a 6 qt capacity (not counting what’s in torque convertor). But every time I open the drain plug, I only get 4 qts out, and adding 4 qts puts it right up to the correct dipstick reading.

Could 2 quarts really be sticking around in the pan? Or could the dispstick be incorrect and I’m running 2 qts low? It’s a B&M Steel Deep Pan with drain plug on bottom at back. And I put the front of the car up.

I’m hoping PO didn’t put in a wrong dipstick? The end of the dipstick has EAC8310 on it, but I can’t find any reference to that part number.

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#2

As a test, try pumping the fluid out of the dipstick’s opening (I did this with a cheap multi-fluid hand pump off Amazon). I was able to get ~5 quarts out that way with no trouble on my '89 (same pan/trans that you have I believe). So if only 4 quarts comes out when pumped out that tells you something–perhaps that it’s a bit low.

I used the pump method to change the fluid not long after I got the car (it was dark dark red and clearly past its prime) when I didn’t have the time/ability to drop the whole trans mount to drop the pan and filter etc.

As for the dipstick–my car has the same one with the same code on it for what that’s worth.

How does your trans shift? Is it rough/jerky? Mine was very bad before the fluid change and replacement vacuum modulator. It’s much better now but still not perfect, especially when cold. Once the engine is warm though 2nd to 3rd is just fine. 1st to 2nd is a little rough if I don’t feather the throttle. I imagine my trans will need rebuilding eventually. I also bought an adjustable modulator so I may adjust it a bit further in the future to see if I can smooth the shifts further.

#3

It shifts fine. Only issue I notice is sometimes a pronounced downshift when slowing down for a stop.

Thanks for checking your dipstick.

#4

Um… how many times are you planning on doing those changes?

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#5

I’ve done 3, am doing a 4th and them I’m done. That should get most of the old fluid out…

#6

Oooook: I’m thinkin,’ after two, the task was fairly well complete!

#7

There is a drain/fill excel calculator out there somewhere…typing in 11 quarts capacity, and 4 quarts drain/fill, it would take me 4 times to reach about 84% new fluid. I may go a 5th exchange for 90% :slight_smile:

Download this, if you have excel, you can change the numbers.

#8

much easier to pull the return line and pump it out. add a couple quarts and pump them threw flushing out the remainder. still concerned, add tranny flush and pump that threw followed by clean fluid.

#9

Try PN EBC4037

E.g. https://www.jagbits.com/product/EBC4037-USED.html

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#10

Seems like I have the correct dipstick.

Perhaps the th400 needs to be level when draining? With me jacking the front of the car up, maybe 1-2 quarts collect somewhere in back of transmission?

#11

Please measure the length from the stop on the handle to the “Full” mark.

#12

It is 27 5/8" from handle stop to Hot full.

OK, found this in your book:
“As a comparative reference, the 1985 dipstick shows the HOT min mark at 27 1/8" (end of measure to the base of the dipstick handle), and the max mark at 26 9/16", while the 1988 shows the same marks out at about 1 1/32" longer.

So 26 9/16" + 1 1/32" = 27 19/32" which is within 1/32" of my measurement, so I’m probably good.

#13

Seems plausible. And, where on the pan is the drain located? towards, or away from, the direction of the tilt?

To be honest I’m hard pressed to remember any car I’ve owned or worked on where draining the pan yielded the stated pan capacity. The only times I’ve comes close is if I drained the pan after the car sat unused for 24 hours or so.

Cheers
DD

#14

A possibility too…i drain it just after driving it a bit, so the fluid isn’t cold.

Plug is at lower part of tilt.

If my dipstick checks out (It looks authentic) then I’ll just stick by it.

#15

I just dropped the pan and replaced the filter- took exactly 5 quarts to get to maximum level when hot. I have heard the Jaguar sump is medium deep, in between normal GM pans. Mine is an ‘88 also.

#16

Ok, I let the car sit overnight, and drained this morning cold. Got 5 quarts instead of 4. Confusion over. :wink:

#17

Us jag guys tend to over-think stuff.

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#18

Oh, trust me, that activity is not limited to Jagaholics.

Try the Rolls-Royce crowd.

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#19

Yeah, I have seen limited commentary on their forums and think your right Paul.