I plan to replace the transmission fluid this weekend or next, and instead of just draining from the pan or sucking it out of the dipstick tube, my plan was to pump it out via the cooler line that feeds from the transmission to the radiator.

Trick is, I'm not sure which line is the supply or return. I could pull either to see, or just let the engine/transmission get hot, but I'd rather avoid both.

So any quick feedback on which top or bottom line is the radiator supply line from the transmission is much appreciated.

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http://shop.ukrtrans.biz/wp-content/...logs/4L80E.pdf

See item 4 and 5 :

https://www.jaguarclassicparts.com/u...e-supercharged

 

So it looks like it is the "top" line fitting on the radiator.

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Someone with hands on would better answer your question as I don't trust technical writers and the names input and output can be crossed . Generally the transmission cooler run across the bottom of the radiator

 

Having previously fitted a supplementary transmission cooler to my Jag I can reliably advise that the input from the transmission goes to the fitting at the left side BOTTOM & the return to the transmission comes from the left side TOP fitting. Item 5 on the parts diagram is correctly stated as "Oil cooler output pipe". Cooler is in the left side radiator tank & flow is from bottom to top.

John Herbert
(1996 Jaguar XJR)

 

I would concur with John Herbert. You would want the hot liquid to enter at the bottom and exit at the top of the cooler, which sits vertically at the LHS of the radiator.

 

Ps Be very very careful loosening the pipes from the side of the radiator. The easiest thing in the world is to snap the pipe off from the body of the cooler which is inside the plastic end cap of the radiator, which will spoil your entire day, and likely the next few too!

 

Radiators are NLA too, and different from the NA version. I've not seen an aftermarket radiator either.