Hello all,

Got a funky problem with my transmission.

I've got a 1996 XJ6 X300 with 204,000 k's (about 126,000 miles)

It is in overall sensation condition, besides the transmission.

The 4HP22 will flare occasionally from 1st - 2nd. It happens if I do not apply too much throttle, and I am going on an uphill slope. It is worse when it's cold.

When I am driving downhill it will virtually never happen, and the shift is very firm, as it should be.

It will happen when driving on a level road, albeit rarely.

I'll again note that it happens if I am only applying slight throttle (up to about 20%)
If I put my foot down significantly, it will virtually never flare.
It's almost as like it gets a bit confused if it should be up-shifting or not?

I have flushed the fluid multiple times, it is at the correct level, and is as pink as could be.
It really is a funny set of circumstances that cause it to flare, even weirder that it shifts very well when going downhill?

Any ideas at all? I want to get some helpful pointers or opinions before I go ahead and get my mechanic to dissect the tranny.

 

Hi Jimmy,

I assume you have the 3.2L engine since your transmission is the hydromechanical 4HP22 and not the electronically-controlled 4HP24.

My first question is what transmission fluid are you using, and how are you checking the fluid level?

The 4HP transmissions were designed for Dexron II/III, which have high viscosities. Newer fluids that claim to be backward compatible, such as Dexron VI or Valvoline Maxlife Multi-Vehicle ATF, have significantly lower viscosities (the fluids are "thinner"), which can adversely affect the performance of the 4HP transmission and torque converter.

Modern fluids I know of in the U.S. that are good Dexron III substitutes with suitably high viscosities include the non-synthetic Valvoline Dex/Merc in the blue bottle (not the synthetic version in the red bottle), and the synthetic Mobil 1 ATF and Redline Oil D4 ATF.

To get an accurate fluid level reading, get the fluid hot with a good drive of at least 15-30 minutes, park on a level surface, set the parking brake, hold the brake pedal and shift the gear selector lever through all gear positions, holding each position for at least 3 seconds (PRND32). This fills the passages in the valve body to give the most accurate fluid level reading. Put the lever back in Park, then check the fluid. The level should be right at the hot max line. Even a pint too low or too high can cause issues.

Cheers,

Don

 

G'day Don,

I'm in Australia, and the mechanic used Penrite Dextron III Trans fluid. Penrite is one of the best quality mainstream oils you can get here.

No issues with fluid levels, just went on a cruise and checked it... it's slightly over, but not by much at all. I requested them to put in a little more because it was slipping, to see if it might fix the issue.
I was hoping by doing 3 trans fluid changes it might fix the issue, but I'm afraid not

Any other thoughts?

 

Hi Jimmy,

I just looked up the Safety Data Sheet for Penrite ATF DX-III (Dexron III type) and its viscosity is typically 37 cSt at 40°C and 7.5 at 100°C, which is close enough to that of original Dexron III (typically 38-40 cSt at 40°C), so the fluid type is probably not your issue. You can download the DX-III SDS at this link:

Penrite ATF DX-III Safety Data Sheet

My next suspect might be a clogged transmission fluid filter, which could cause low fluid pressure under low to moderate load. Has the filter on your transmission been changed? It's an easy job on your gearbox. Use a high-quality filter (usually German) such as a Mahle, Mann/Wix, Filtran, etc., and replace the gasket (Elring, Fel-Pro, etc.).

I don't know if a problem with the gear selector cable could cause your symptoms, but it is worth checking the cable connection at the transmission for looseness or corrosion and to confirm that when the gear selector lever in the J-gate is in D or R, the lever on the side of the transmission is securely in its corresponding detent.

You don't have a Transmission Control Module and I don't remember if the 4HP22 can trigger any OBD diagnostic trouble codes in the ECM, but it might be worth checking.

Hopefully motorcarman will chime in with some additional ideas.

Cheers,

Don