MY friends 1990 ranger 4.0 2wd auto will not shift from 1st to 2nd unless you let off the gas. Once in 2nd, it will shift in its own into 3rd and OD. What causes this?

 

Could be a bad shift Solenoid.

 

Also maybe gum, varnish, or sludge deposits, even if he's been good about scheduled maintenance call outs, for tranny fluid & filter changes.

I don't abuse my tranies, have been really good about timely & quality tranny fluid pump outs & filter changes & have still developed some shifting problems.

I've had good & so far, lasting results on clearing, delayed up & harsh down shifting, on my 94 Taurus AXOD & 99 Ranger 5R55E trannies, after doing a Seafoam "TransTune" detergent routine, long enough for the problems to clear up, then dropping the tranny pan to clean it out, changing the filter & doing a Full tranny fluid pump out.

If his tranny has been neglected & has plenty of deposits, he'll want to go about any "clean up" process, slowly & carefully, so as not to break any deposits up too quickly & clog something else up.

Most deposits come about slowly, over time, so imo should be removed that way.

My trannies have always gotten service at the "Severe Service Interval" (so the observeable deposits have always been minimal & the tranny fluid has always looked, felt & smelled ok, but I've still had problems), anyway I began my TransTune treatment, at Half the recommended dose & waited a few days, watching the fluids condition & color & to see how the shifting changes went.

In my case I begin to get posiive results in about 3-4 days & the fluid still looked ok, so I added the remainder of the TransTune & drove until the problems ceased, then did the pan drop, filter change & complete fluid pump out.

I didn't leave the TransTune in there.

If his fluid is in poor condition & you can see varnish, or other deposits on the dipstick, maybe consider first dropping the pan to inspect things inside for the types of deposits, cleaning the pan & changng the filter & doing a full fluid pump out, with some inexpensive WallyWorld fluid & see how that goes.

If the problem persists & the tranny fluid hasn't gotten too dirty & the deposits were heavy, maybe try a half dose of TransTune & see if things improve.

Then if that goes well, consider adding the other half can of TransTune, watch the fluids condition closely & see what happens.

If the problem clears, & the fluid is dirty again, then consider another pan drop, filter change & another fluid pump out.

If things get better, then imo it's likely at least partly a deposit problem, maybe if he's lucky, all a deposit problem, as mine seem to have been.

At any rate, ease into any cleanup program, so as to Slowly dissolve any deposits, so they can be held in suspension in the tranny fluid, or captured by the filter.

If all that comes to naught, then it's likely a mechanical shift solenoid, or valve body problem.

Just a bunch of my happenings & thoughts for pondering.

Let us know how it goes.

 

Check out the Explorer forum. My 95 Exploder did the same thing, shift solenoid and trans flush did nothing, Ford service manuals lead you all over hell's half-acre, and it was my ex's daily driver, so I didn't really worry about it at the time. I never bothered finding out what the root cause was, because I dumped her and sold the pile to a co-worker, with a spare tranny that I hadn't bothered to install, either...... good luck!