Had my Jag for a testdrive today, and discovered that it only runs in first gear, and reverse.
The first thing i suspected was oil level, and yes - it was low. I filled up with new oil and it's now on maximum level (hot) when running (I cycled trough all selector positions).
Still no upshift when driving. I have no experience with this transmission (GM400?). Whats the next thing I should check?

I've been under the car and checked. Beside the speed selector cable there is a electrical wire on the left side (speedometer sender?) and on the right side near the dipstick guide tube is a thing where a (vacuum?) hose is connected. I can see this (vacuum?) hose follows the dipstick guide a bit, but can't find the other end of this hose. Where is it supposed to end up. What does it do?

This is the last thing i need to sort out before I can drive my cat home (beside finish welding on the Triumph spitfire so I can make room for my Jag).

 

The vac hose goes to the A bank inlet manifold. I think the vac signal it gives to the gearbox affects the point at which the gearbox changes up, as in later changes on lower vacuum, as it thinks the throttles are wide open and the car therefore trying to accelerate fast.

There are two sets of wires on the LHS nearest the front are the kickdown switch wires, these are there on all GM400 gearboexes used in XJSs. Earlier models like yours and mine have two sets of wires on the gearbox LHS, speedo transducer and kickdown wires. The transducer wires come from towards the tail of the gearbox and come out or a round-shaped thing screwed horizontally into the box side.

Greg

 

The vac does determine shift. Pull the hose at the transmission: The engine revs should rise. If not hose is restricted by kinks, collapse or debris. (I am assuming you do not have problems with a high idle having to turn the AAV completely shut which would indicate a vac leak somewhere in the hose or it's connections.) BTW, the oil level after a 5km drive should be at 1/4 above ADD. If full the oil may well foam and you may have all sorts of odd behavoir. In particular that applies if driving hard or on hot days (or if sitting on an incline).

An afterthought: If the kickdown solenoid is permanently on .... Pull the kickdown plug and testdrive.

PS, where in N are you? I'm just outside Oslo.
DS

 

Most likely you have a governor gear that has failed. They are made from plastic and if the vehicle sits for a long time rust develops on the drive gear and then the plastic driven gear on the governor just wears right out very fast. The failure mode is as you describe, only first and reverse.

 

To clarify, no upshift out of first AT ALL? If so, I'd suspect the governor as Greg says.

Or, will it upshift out of first very late (40+ mph) and very hard ? If so, suspect the vacuum modulator or hose to the vacuum modulator

Cheers
DD

 

to all: thanks for your reply!

Doug,
I have kind of limited road for test-drive, so I was not much over 40 mph when testing, but with light throttle it should definitely change to 2. gear i that speed, but stayed in first gear all the time.

Greg
The car has been stored for about 2 years time before I convinced the owner to sell so I guess that will count in under your governor failure theory.
Is this possible to fix with the transmission in the car?

Per
I actually had a LOW idle problem, but with help from this forum i fixed that by adjusting the "butterfly" gapto the correct setting, so there is nothing right now that indicates a vacuum leak. I will of course check the vacuum modulator and hose.
But a thing i noticed is that in several pictures in manuals and on net , the vacuum modulator is mounted in a way that it points straight out to right side of the transmission, but on my car, this modulator seems to be bend a bit, pointing slightly upwards. Maybe this is the actual problem?

PS! Per, I'm in Stavanger

 

Found a chapter in "Experience in a book" that describe in detail how to check/replace governor nylon gear going through the access hatch in the transmission tunnel!

what a brilliant book!

 

The governor seems to be ok. Over to the next on the list what will be the vacuum modulator.

Waiting for parts...

 

A new vacuum modulator did the trick!

 

Hoooray !


:-)


Cheers
DD

 

had a feeling. im sure if you wouldve pegged it and revved to 6k rpm, it wouldve shifted into 2nd.

 

Great stuff!
Greg