Jaguar Repair: automatic gearbox,car wont go forward!, transmission expert, borg warner

Question
QUESTION: Hi,I bought an XJ 4.2 C, it has been garaged for 18 years. We drove her onto a trailer and she ran well considering. When we got her home she reversed no problem but refused to go forward. We have changed the oil with no improvement. She will creep forward but you have to rev her hard. Any ideas?

ANSWER: Hi Bob,
I am not an automatic transmission expert but it sounds like you need to clean or have the valve body cleaned and the two bands adjusted. Also system pressure tested after the valve body is cleaned. You didn't tell me what year it is. If it is a series III, it is a Borg Warner 66.
Most any transmission shop here in the US works on them but I don't know about the UK but I would think they would know the trans too.
Howard

---------- FOLLOW-UP ----------

QUESTION: Hi Howard, many thanks for your quick reply. The jag is a 1975 xjc 4.2. We have had a look but cant locate the valve body. Can you tell me where to look for it?Also can you  tell me if when adjusting the bands do you have to do them one at a time or at the same time.If this doesn't work and i have to replace the gearbox, do i have to take the engine out to do the job? thanks Ben

Answer
Hi Bob,
I am not familiar with the 75 XJ-6 C box as it is not a BW 66 but possibly a BW 65 or another version. Plus I have no idea what the UK used back then but all the info I can find says it should be a BW 65 and the valve body should be the large intricate looking plate as soon as you remove the pan.

You would be foolish to attempt to disassemble a valve body on any automatic transmission without a manual to refer to as many have many small ball valves, springs and plungers that can fall out when you take it apart to clean. There also should be a large screen that needs to be cleaned. That you should be able to clean or replace without getting into trouble.

The amount of trash you find in the pan and screen usually tells you roughly the condition of the box. Plus the condition of the oil. Dark burnt smelling oil and a lot of trash in the screen and pan is an indication of the need for an overhaul.

Howard