So my XJS has started sounding like it has gravel in the transmission which I assume means an expensive overhaul. This gets me thinking that if I am going to spend $$ should I look at an upgrade instead. This car would benefit from 4 instead of three I think. Are there any common or easy upgrades that can keep the original look inside but provide a better transmission with a bit more low down pickup?

 

700R4 / 4l60e has a very deep first gear that will help get the car moving and would be better even with the 2.88 ratio diff. An upgrade to a 3.31 diff would make the car very quick off the mark and still cruise sedately at high speeds in 4th and locked up. This is one of the few upgrades thst "could" pay for itself in fuel saving if you drive it long enough.

 

What is involved in such a swap, please?

 

I have a 4L60e and 3.58. 2000rpm at 100km/h and mighty sprightly out of the blocks.

Trans swap if using a 4L60e you will need.
Bellhouse adaptor and torque converter spacers
Custom dust cover.
I made a custom trans mount
New drive shaft.
TCU and wiring harness

If using a 700R4 no TCU but TV cable and associated mechanism on the throttle capstan. IMO I would go with the electronic version, TCU's are reasonably inexpensive these days and give you program control over the transmission.

The stock TH400 shifter works as is with the 4L60 albeit that 1st on the shifter is 2nd for the 4L60.

One thing I did wrong was use a stock 4L60 torque converter and this limits engine to about 5500rpm because the TC was from a V8 Holden and not balanced for 6500rpm. You can hear and feel the hunting around 6000rpm.

 

Thanks Both, very helpful, sounds like it’s doable and gives good results but a bit of work, not a straight swap. Will discuss with my mechanic and see what he is up for.