I've noticed (mostly when the car is cold) that I'm getting some pretty firm, harsh gear shifts, both upshifts and downshifts when braking to a stop.

The car has 60,000 miles and the transmission fluid and filter was changed at 54,900 miles. The oil is nice clear red, and smells brand new.

The only issue I see is that the fluid level looks too high, after driving the car on a long trip (250 miles) I checked the fluid on level ground in park with the engine running.

The fluid was practically covering the entire white plastic end of the dipstick, which is about an inch higher than the HOT MAX line on the dipstick, and about 2 inches higher than the HOT MIN line.

It was a small shop that did the job, and I have a feeling they just drained and refilled the transmission instead of flushing it to get all 10.8 quarts replaced?

Would too much fluid cause harsh shifts? The oil isn't foaming from it, but I don't want to cause any hard part failures with such hard jerking shifts.

Thanks,
Nick

 

Nick,

I seriously doubt that fluid level is your issue, as these old style transmissions are significantly more forgiving that the newer so called sealed units.

If the harshness has developed since the intervention of this guy, I would suspect the specification of the fluid used is causing the problem. If it was harsh prior to his fiddling, then NO.

I run Synthetic ATF (Multi vehicle ATF) in all mine, and have done so for about 15 years now, with no ill effects. My X300, same trans as yours without the electronics, has benefitted significantly from this Synthetic fluid. Nice and smooth, up and down.

My suggestion, therefore, is to drain this unit, either via the drain plug (if fitted), or simply undoing the dipstick tube nut, and refill with fresh fluid of your choosing. If this sorts it out, great, if not, maybe an electrical connector issue, but that is something I have NO idea about.

 

Thanks. I purchased the car with about 57k on it, and that transmission change was done about 3k miles before I bought it, which was July 2011.

I was interested in finding out if synthetic fluid could be used in these transmissions.

My Oldsmobile (which originally was spec'd for Dexron III) and all other GM vehicles of the time, had a TSB which recommended the use of Dexron VI which is fully-synthetic.

In the TSB it listed the improvements (Over Dexron III) as:

-Clutch Friction Stability: Improved 100%
-Clutch Durability Due to Fluid: Improved 120%
-Oil Film Thickness: Increased 20%
-Fluid Oxidation: Improved 100%
-Foam/Aeration: Improved 120%
-Shear Stability: Improved 200%

I was just wondering if the synthetic would have a detrimental effect on the seals.

I was also thinking about buying a cheap used Transmission Control Computer to see if maybe it was a computer issue.

I did suction out about 3/4 of a quart of fluid from the dipstick tube last night. I drove the car and it shifted the same. Once I got back, I double-checked the level and it was right between Min and Max on the dipstick.

Thanks,
Nick

 

OK, the mud is clearing somewhat.

These transmissions and the car attached are built to be USED, so sitting around is against the grain.

The fluids break down, even with NO use, and atmospheric moisture contamination is #1 on the list. Dried up seals is next, and so on.

I would drive it about 30 miles, at least, and then using common sense (so as not to burn the fingers), drain the fluid.

Refill with Syn ATF. I use Nulon or Penrite down here, probably not in your market, but super expensive Syn ATF is not needed here.

Drive it again for at least 200miles over a short time frame. Make that trans actually "work", as in as many gear changes as possible, then repeat the drain and refill.

I did the X300 8 times in 6 months, and the difference was extreme. The 02 S Type has now been done 6? times in a year, and that also is sorted significantly.

The new fluid does take time to "wash" all the collected gunk out of the internals, and numerous drain and refills is the safest way (MY OPINION HERE) to do this.

Once sorted, and you again have the warm and fuzzies with the Jag, drop the pan, replace the filter, and refill again.

Please remember what I said earlier, these cars are built to driven, and cost more $$ to have sitting around than actually driving and enjoying them. That is why I have reduced the fleet from 9 to 2, I simply cannot keep up with storage maintenance now.

 

I've had the car 4 months, and I've driven it 3,000 miles so far, so I will not let it sit. It is my daily driver for now. I've just done two 450-mile round-trip drives in the past month or so, and the car has been phenomenal.

If I remember correctly, this car does have a drain plug on the transmission pan, which will make drain and refills MUCH, MUCH easier. Looking at the manual, each drain and refill is about 8 quarts of fluid or so.

I'll give it a go. Just good synthetic ATF, no additives required, correct?

Thanks for all your help, you've been immensely helpful!

-Nick

 

AHA, a drain plug, watch your back I will steal that pan if you look away, as mine has no plug, must be a "poverty pack".

Watch that oil quantity, as they are NEVER correct. That 8qts is a "dry fill" spec, a sin a stripped for rebuild unit.

Mine takes just a smidge under 4ltrs at each drop and refill.

No additives is correct. Some use them, I do not.

Daily driver is GOOD, and none of this "for now" in my book, it is a keeper. I have put 66000kms on mine in 3 years.

 

Thanks Francis,

I agree with you about keeping it a daily driver, but I want to be able to enjoy for some a long time to come. These are so hard to come by in the condition this car is in. I'd still drive it a reasonable amount, but I don't want to see it rack up miles like an 80's Honda beater.

Thanks for the tip about the fluid amount. I was checking ALLDATA, which gave an incorrect listing. Opening up my Service Manual, it specs 4.5 quarts /4.25 liters for the drain and refill amount.

I'll verify that there's a drain plug, but I'm pretty sure I saw one last time I was down there draining the engine oil, replacing the differential oil and greasing the u-joints.

Thanks for all the great info!
Nick