Intermittent shifting issue 1995 Ford Bronco

Question

I've been fighting an on again off again issue with the transmission, I am at my wit's end.

The truck will occasionally start shifting hard, and from what I've been told this is due to some sort or electrical issue that causes the PCOM to go into a weird mode.

The transmission itself is freshly rebuilt a little over a year ago, I took it to get serviced for this issue but they basically said it's really hard to diagnose and find without simply replacing bits, since the truck is OBD1 and anything in the wiring or components on that circuit could be affecting it.

Usually when this happened the central guage cluster would go out, signalling something was up (no speedo, no ODO). I replaced that part of the gauge cluster AND the VSS, that seemed to fix it for a while.

Today it began shifting hard again, but the gauges were acting fine, so idk what is causing the issue.

At this point, I'm ok with tearing into it and just replacing bits until something changes, even replacing the wiring harness if I have to.

Is there a specific shop I should take it to, since it seems to be an electrical issue?

Thanks for your help.

Answer 1

This very issue is how I bought my own '95 bronco for cheap. There are a few things to look at, but first you should pull codes. You should be seeing a check engine light or the O/D light flashing if the trans is bucking. Are you getting codes 211 and 452?

First, some things to clean, in no particular order. Test drive after each:

-Use a multimeter and some paper clips/staples to back-probe the TPS and check the voltage with an ANALOG volt meter. If it is not a gradual increase in voltage and does funny shit... replace it. This is what solved my initial shifting issue.

-The connector to the shift mode selection switch on the side of the trans. Unplug/plug it in a few times and make sure the contacts are clean.

-Remove the rear diff ABS sensor and clean the tip off. Make sure the contacts in the connector here are also clean.

-Make sure your intake tract is clean. Pull the throttle body off and chip all the shit out of the intake that the EGR has let in. Use a vacuum cleaner when you do. You will be quite surprised as to what is in there.

-There is a large connector in the engine bay on the driver's side that is held together with a bolt. Probably 10-20 connections in it. Pull it apart and make sure it's clean in there.

-Open the ECU and look for swelled up capacitors. If any are, STOP. Get a new one, rebuild kit (if you can solder good) or have it rebuilt (Ebay).

-If the problem typically happens after you've coasted to an idle while stopping, then replace the IAC valve. That bastard can cause a lot of dumb issues... but clean the intake when you do this too. You might as well. Seriously I'll bet your intake is filthy.

-Check your ground connections, EVERYWHERE. Make sure the trans case is grounded. Make sure the engine is grounded. Make sure the ECU has a good ground. Ford loves grounds. Grounds hate corrosion. Corroded grounds make fords angry. Please, consider the grounds.

Comments

I have the same problem with my 95 Eddie Bauer.  Every time this happens the display panel that shows temperature and direction travelling is off.  What could the problem be relating these two things?

Answer 2

Does it shift hard through every gear or just in and out of overdrive?

Comments

Every gear, I believe (I think overdrive was fine, not sure though). From a stop it would slam hard into first, shifting late at around 3k RPM instead of around 2k. Same high rpm shifting for the other gears, but it didn't jerk on the way back down (it did a little, but just enough so I noticed the gear change. It wasn't violent like the upshifts.

Answer 3

I know some shops offer warranty’s on rebuilds. A local shop just rebuilt my f150s and I got a year warranty. So it might be worth checking out that option.

Comments

I got a two year warranty. They say the transmission itself is fine, and it's an electrical issue that is affecting the PCOM. since that isn't covered under the warranty, they basically said it's not an issue with the trans and sort of washed their hands of it.

I make them out as the bad guys, but they are a reputable shop and I haven't heard anything bad about them. The guy who last touched it basically said he couldn't find the issue, and it fixed itself so there wasn't a good way of figuring out what is wrong if it was running fine.

That's perhaps the most frustrating about it being on/off, if it were consistent at least then you could figure out what maybe causing the issue.

Answer 4

So, I chased this issue for years on my 1992 F-150. It ended up being the PSOM (Programmable Speedometer/Odometer Module). The circuit board on the back of the speedo cooked itself and was creating an implausible vehicle speed signal. The speedometer and odometer functioned perfectly; there weren't any symptoms but terrible "rebuild your transmission now" shifts.

I know you said you replaced the cluster once but it's possible (even probable) that it failed again. I pulled 5 junkyard pcb's as potential replacements as I didn't know their mileages. 3/5 were bad. Also have successfully fixed a friend's '95 F-150 and a coworker's '96 Bronco the same way.

Comments

Iirc there's a place that rebuilds them. I think I may just go that route, rather than try my hand at the lottery again. I figured that may be the most likely culprit.

Maybe this time I can get a Lightning 120 mph speedo.

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Did this issue cause your ABS light to come on?

Answer 5

Get rid of it and buy a manual like you should’ve to begin with

Comments

They didn't have any manual broncos after 92 iirc. Definitely none with the 5.8, and the manuals were only on the base models. I've been wanting a black Eddie Bauer 5th gen for a while, hence why it is the way it is.

Answer 6

Hey man, did you ever figure out the issue? Same issue with mine i got going on.