bobby150

Is anybody out there aware of issues associated with trading an automatic transmission (4r70w) with a 5 speed (zf542)? Obviously, the zf is from a 250. A buddy of mine changed his out on his 86 150 with no problems. When I switched mine out on my 95, I seemed to have developed an ignition miss or "buck" I can't seem to find the origin of. His truck is speed density while mine is mass air, but I wouldn't figure that would make any difference. Or would it? Any ideas would be greatly appreciated.

The problem is I'm not throwing any codes, except "excessive speed in park". I've replaced and/ or tested everything ignition related. I replaced all vacuum lines. It seems to happen less often in cooler weather but not always. I'm beginning to think it may be the ECU. But not sure where to go from here. It's my daily driver I use for work.

Chris_1

iTrader: (1)

Did you change the ECU to one from a manual truck ?
Your buddy wouldn't have that issue because his trans is vacuum / governor controlled.
The 4R70W was electronically controlled by the same computer that controls the motor.
I can see some potential for a problem there maybe.

bobby150

That makes sense. What problems would they be?

Problem is that I've not found anything suggesting Ford made anything other than a mustang with a 302 maf, manual transmission. I've got a 1995 ECU, but it's speed density as I found out. I found a couple forums suggesting an A9L mustang computer and having to re pin the wiring harness and add an 02 sensor. Other forums I read suggested no problems. So I'm not sure how or what to fix...see about having the computer reflashed?

Chris_1

iTrader: (1)

You may be able to order a 'stand alone' computer that's designed to just run the motor and not the motor/transmission combo.
If of course you eliminate every other possibility first.
You've replaced ignition parts but maybe some of them could be tested just in case they were faulty out of the box.
And there's the possibility of something else acting up coincidentally at the time of the swap. You can test the TPS and the fuel pressure would be a start. Just in case it's all unrelated to the trans.
But I would suspect that if you're getting a code related to the trans that isn't there anymore, the possibility exists that the computer doesn't know what to do with the information.

bobby150

Great thoughts! I have replaced and tested the TPS, in fact replaced it twice since all this has been going on. So I'm fairly positive it's not that. The fuel pressure is a good idea to try again. I spent a day with my hood off and the gauge duct taped to the windshield watching as I drove. I'll look into the computer option as well. I may have found a guy who can reflash the ECU, but I'm not sure how all that works and if he'd be able to delete the transmission from the computer. I appreciate all your suggestions. This has been going on for a year and I've spent way too much money and time trying to get it running right, only to hit dead ends.