New to the forum but not new to cars. I have been searching but can't find any reason not to switch my tranny to synthetic. I plan to use Mobil 1 "multi Car formula" Anyone have any concerns? The car is new to me and I have no records although the car is nearly pristine. It has been taken care of cosmetically, I hope the PO was as meticulous with the mechanics. I don't know the last time the trans. was serviced, so I decided it was time to do one. The car is a '91 XJ-6 Sovereign with 146K. The only tranny issue I have noticed is a slight shudder at 52mph, I think when the torque converter locks up. Other than that it seems to operate perfectly. I just remembered it does need the shifter bushings replaced as the shifter is a little loose and sometime needs to be nudged to trip the neutral safety switch. Is this a difficult job? Thanks in advance for any advice. This is a beautiful car and I want to keep it that way.

 

Trans service is recomended at 30K mile intervals.
The only requirement for the 4HP24 is Dexron III specs. You can use Dexron IV as an upgrade so look at the label for compatability. I think that for the next gearbox service for my 1992 XJ40 I will look at synthetic fluid. For many years I have been using MOBIL Dexron Premium fluid that I have obtained from working at the dealer but lately I have been running low so time to stock up on fluids.


bob gauff

 

IIRC the label says the Multi-Car formula is Dex III H replacement. Since it's Dex III, I guess it's ok for my car. I'm just doing a drain (and filter) and fill, I'm guessing I'll get around 4 quarts out? It may not make any difference at all. I will report what I find.

 

Well, I did the drain/filter/fill yesterday. I have only driven the car about 15 miles since. Shifts were very smooth before and still are. Only concern I have is the 52 mph shudder. It drops 300 rpms and lurches/shudders a small amount. I think this is when the torque converter locks up. Is this common? I was hoping the new fluid would remedy this, maybe with a little more driving. Thanks for all the help, I love this car so far.