E4OD issues

[vanilla gorilla]

So I am hoping someone here has maybe run into this issue before and may have an idea what the solution is. My 1990 has the E4OD and the 351. When I accelerate the 1st to 2nd shift is normal. 2nd to 3rd and third to OD shifts rev high before engaging the next gear and the rpms are higher than they should be normally. The weird part is that when in 3rd or OD if you hammer the throttle, the rpms drop to what I would think would be normal. As in say I'm going 60mph down the highway, it's running about 2500-2600 rpm. If I hammer the throttle it will seemingly "Shift" fully into gear and the rpms will drop to about 2100. Same thing in 3rd. Say I'm going up a hill and it down shifts to 3rd, rpms are about 3000, hammer down and it'll drop to about 2600. Any ideas?

[philofab]

Has the MLPS sensor been updated? OD light flashing?

[300]

The RPM drop when you get on it happens when the torque converter locks up. All of the E4OD's I have driven, diesel or gas, do that when you go from light throttle to heavy throttle, and they did it from when they were new to 300K miles. The flare on shift doesn't sound good and I am not sure what you have there. LIke Philo said, is the OD light flashing?

[vanilla gorilla]

The OD light is not flashing. I don't know about the mlps sensor. I have not done anything to it. I have had a diesel with the e4od but that never did anything quite like I'm describing with the rpms. Also if I accelerate hard right from the start, keep my foot hard in it through all shifts, it will shift almost normally.

[philofab]

Early MLPS sensors had issues keeping water out and caused a multitude of problems, there is a TSB and an updated part / connector to fix issues.

Also, you may possibly have a TPS issue or it's out of calibration. The TPS is needed for the computer to adjust line pressure.

If your speedometer has jumping issues or does not work it can also create that problem.

What's odd, it once the computer senses a slip, it causes a check engine light, code, and will up the line pressure to 100%. 100% line pressure creates really hard shifts at anything but full throttle.

[ChaseTruck754]

If it's a 1990 truck - is it new to you?

May be a long shot, but may be worth a check - I have heard of guys wiring the check engine indicator light on OBD1 vehicles to the start wire on the ignition so the light comes on at engine startup and goes off after, and won't actually come on if there was code thrown. Maybe this is why the check engine light doesn't come on if in fact a code is there. Have you tried to put a scanner on it & pull codes?

[vanilla gorilla]

I've had it a couple years now. It's been shifting like this for about a year and a half. Drive it everyday. I have a parts bronco with a c6 I had intended to swap in, but the more I think about it, the more overdrive sounds appealing. I haven't tried pulling the codes. I should do that.

[vanilla gorilla]

After dealing with the trans not shifting right for over a year, I have found the solution. I am almost embarrassed to admit the problem. Turns out it was my led tail light bulbs causing the torque converter to not lock up. Put in standard 3157 bulbs in last night, shift like a champ now!

[RyanDS650X]

That's weird! I had issues with my cruise not working and running lights on my boat trailer not working with the LED's. They need resistors so they communicate correctly with the rest of the truck.

[RyanDS650X]

http://www.fullsizebronco.com/forum/sho ... 594?page=1

Pay attention to post #9