Hello all, I have come across a 97 Mark VIII for a good price in very good condition. I am thinking of buying it but the owner told the trans may soon go. I'm still interested and thought about swapping in a 4r75e because my Expedition has one and I love the **** out of it. I have the capability to do it myself so that's the route I'm going.

Is there a way to do this even if it involves extensive wiring work. I love doing wiring so I'm happy to take the time and do it correctly. It's an art sort of... Any suggestions to help me get to the goal?

 

Has to be from a 2wd vehicle.

Biggest problem is that the output shaft on a 4r75e will either have the wrong number of teeth to drive the speedo gear or no teeth at all. No teeth at all will require a complete tear down to replace the output shaft with one that does. Otherwise for the wrong number of teeth a correcting speedo gear can be installed. The ring gear is going to have 24 "holes" instead of 6. Replace that when you are in there for the output shaft or tune for the difference.

Electronically the issue will be either a need to rewire the harness on the car to work with the new electronics or replace the internal electronics with the old style stuff. I can help you with that through diagrams and write ups. Easy stuff here.

It's not a horrible job. Just know what you are getting into before you get into it and it's too late.

D

 

Thanks for the reply! So the output shaft needs to be replaced and tuning is necessary? I'm going to tune it anyways, that's why I'm putting a 4r75e in instead of another 4r70w. I figured it could shave some time off of my 0-60 too.

Where do you think I should get my trans PCM from? I know the Mercury Marauders had a 4v and 4r75e but I would think it might be hard to get a hold of one of those. The 3v motors had them too for awhile but they were VCT engines and I don't know that the wiring harness would work with a 4v. What do you think?

 

Why not use the computer that's in the car now?

D

 

Because I think they wouldn't work right. The 4r75e is electronic Shifts and T/C to my understanding and the 4r70w is old school. Am I correct?

 

There is not much difference between a 4r70w and 4r75e. Ford changed a few parts to work with the electronic throttle body and some durability upgrades. They work the same and both are controlled by the PCM. If the 4r70w is good then I would use that and keep the 4r75e for parts just in case the 4r70w needs rebuilt.

 

Actually the PCM in that MKVIII will run that transmission just fine as long as the car doesn't get too powerful. At that point it might not be able to keep up, but you would have bigger issues to deal with.

For your purposes, no need to change the PCM just for that transmission swap as long as the other things mentioned above are addressed. The PCM will never know the difference.

D

 

Thanks D, I appreciate your quick and helpful responses! I don't think this mark will ever see over 500 hp but you never know! If I do decide to build it that big I'll definitely do more upgrades all around. I'm not one to cheap out on something important.

That being said, do you think the stock PCM is really going to be able to think as quickly as the 4r75e needs. I'm doing the install because I'm going to seriously tune the trans and engine when I get it to make this a pretty fast car. I like my shifts as quick and powerful as my trans can handle. Thanks again

 

Thanks for that info 70f10longbed. I did not know the trans were identical.

You bring up the ETC, the Mark VIII as you guys my know is old fashioned FI Throttle. Will they still work?
And you also mentioned the PCM's, the one to the 4r75e I am told is faster than the older PCMs. Do you know this to be true?

I'm looking for every ounce of shift power and control at my fingers when I touch a button on my tuner.

Thanks

 

By faster PCM I mean more processing power.

I know the 4r75e in stock form can shift super hard or very unnoticeable. And also very quick and almost hang up a gear for a few seconds. (man that makes me mad)

Can I still get the full ability to control that with a programmer made for the Mark VIII. BTW do they even have those for this thing? The car is sort of before its time.

 

Seems like this is getting overly complicated and it really needn't be.

Maybe it's best to explain that the transmission is a "dumb" device. It relies totally on external computer control other than minor differences in the valve body and control spring setups for shift timing and firmness and those can be addressed on the older PCM through tuning

The computer controls the 2 shift solenoid, a torque converter clutch solenoid and an electronic pressure regulator. All of these from the newer transmission are compatible with the PCM from the 97 MKVIII. That is not the case with some earlier vehicles however in relation to the converter clutch solenoid. No worries with that on your 97.

Fortunately you are looking at a setup that will work perfectly with very minor modification electronically as the transmission truthfully "needs" nothing different in a PCM than what the stock MK PCM provides. Everything that needs to be controlled for exactly normal operation is there. The only change required electronically is that the wiring harness on the vehicle side needs to be re-pinned since the newer transmission has a different configuration in its connector.

I have helped with and been part of literally hundreds of these swaps. They are only as complicated as the people doing them make them because hardware wise it's as near straight in as you can get without being straight it.

The things that have to be addressed were posted earlier. The output shaft must have speedo drive teeth on it. As long as you are ok to correct those issues you are golden.

D

 

Ok. Thank you very much for clarifying. I thought transmissions handled themselves based on communication with the engine. It may be another 2 months on this trans or another 10. Either way I won't do the work until it quits, at which point I'll rebuild it and put it away for a 4.6 turbo ranger build.

I'll be sure to swap in a speedo output shaft and when the time comes I will be back for a wiring diagram to re-pin the harness.

You've been very helpful! Thank you!

 

i know this is a old thread new member looking for a diagram for the pin relocation going from a 4r70w to a 4r75e trans is in a 2003 f150 4x4 it's in and i need to relocat pins on vehicle side i have the 4r70w pin diagram need the ne pin location any help will be greatly appreciated thanks

 

I've got some info on my site.

http://www.bcawebstore.com/harnessrepinwires.jpg

http://www.bcawebstore.com/harnessrepindiagrams.jpg

 

thanks for getting back to me i'm having trouble trying to figure out which way my plug is pointing on my diagram i took a picture of what i thought was the way to lay out my plug tried it on my truck but no luck i'll try to post a picture on this post if i can