Hi guys I've been trying to get to the bottom of this problem for awhile now and I'm just stumped. My 98 ford ranger with the v6 4.0 auto has a problem with the reverse gear when the truck is cold. When I first start the truck after its been sitting there is no reverse. All the forward gears work perfect, once I take the truck around the block reverse works like it should, it may take an extra second to engage but will work great once it's engaged. I hope I'm not the only one with this problem. Any help would be greatly appreciated thanks in advanced.

 

Having owned a transmission shop for some years awhile back it sounds like your truck has morning sickness. Basically the seals inside the transmission are getting hard and causing a pressure loss to your reverse drum. After the truck warms up the seals expand somewhat and everything works the way it should. As a temporary fix you could try a transmission leak sealer which would expand the internal seals but, it will also deteriorate the seals rather quickly. I would suggest just living with it till you can get a rebuild on the unit. Hope this helps and good luck.

 

+1 ^^^

All automatics regardless of manufacturer run on ATF fluid pressure.
Automatics have an internal ATF pump, called main or front pump, its the only pump, it is at the front and driven by outside case of torque converter, so pump spins at engine RPMs, from idle to 5,000rpms, obviously, the higher the RPMs the more it pumps so the higher the pressure
The pump has a max pressure valve so you don't blow out seals and gaskets

Automatics have internal Clutches and Brakes(bands)
The Valve Body routes the Pressure from the pump to these clutches and bands, the clutches engage and disengage the rotating parts of transmission, the bands(brakes) HOLD tight the parts that shouldn't spin, this is how Ratios(gears) are selected.

For Forward gears you need minimum pressure of 125psi in the valve body
For Reverse you need 175psi pressure

If there are leaking seals and/or gaskets then pressure will drop too low for Reverse to engage but Forward works just fine

So a pressure issue in an automatic often shows up first with slow or no Reverse, raising RPMs can increase pressure but only up to a point

Your 5R55E transmission has 6 solenoids that control pressure flow thru the Valve body
One is the EPC(electronic pressure control) solenoid, it can cause lower pressure and HIGH pressure(harsh shifts) if its not working 100%

Transmission shops can do pressure tests while transmission is shifting thru its gears
You can to, need a high pressure gauge, 300psi minimum
The pressure tests can tell you where the problem might be

If its a low pressure issue, which is what your description implies, that can cause clutches and bands(brakes) to wear out faster, even though it "seems" to be fine in Forward gears there could be some slipping which causes heat which causes high wear on those parts, like "riding" the brakes or "riding" the clutch in a manual trans

Yes, "trans fix" or similar additives soften seals and swell gaskets to get better seals and less pressure loss, so do work if thats the issue
Never heard of these damaging seals or gaskets(shoreguy would know better than me) but they do NOT fix the basic problem so unless its fixed transmission damage can occur over time

Generally speaking replacing the Valve Body, solenoids, and separator plate solves 99% of pressure issues, and it can be done without pulling out the transmission

 

Once upon a time in the previous century.. I had an aerostar minivan that did the exact same thing. I drove it that way for 6 months before trading it off. It was gradually getting worse and towards the end it was not going into R unless having been driven like 30+ minutes (fully heated up)