1988 F250 XLT 7.3 idi - Which auto transmission?

[AmigaDave]

Forgive my ignorance and impatience. I have spent hours over the last few days trying to figure out which transmission the 1988 F250 XLT w/7.3 idi engine I just purchased has inside of it. I tried checking by VIN, with no luck, and joined here in hopes that some of you can help me out.

My "new to me" truck has (probably) about 329,000 miles on it, but still runs strong, so i don't know if it has ever been rebuilt, or if all 7.3 idi engines last this long while still running great. The transmission only shifts into 3 forward gears, and will not shift to a higher gear until well over 2000 rpm's with no load, and shifts are "hard". There is so much oil leaked under the engine & transmission, it is difficult to tell if it is from one, or several leaks, and if it is from the engine, or the transmission, or both.

The first thing I did after purchase, was an oil and filter change, plus all other fluids flushed and replaced, including the gear oil in the differential. I have purchased some Automatic Transmission Stop Leak, because I did not want to pay the extra expense of having the drive through oil change guys add it, at an extra 300% markup, but now in hindsight, I probably should have just let them do it, as I don't know how hard it is to put this transmission stop leak into my transmission.

I have read alot about the E04 automatic transmission for 7.3 idi equipped vehicles, and assume that stands for an electronic overdrive 4 speed automatic transmission, so I am wondering if perhaps my transmission is faulty, and the overdrive is not working? On the freeway, I am seeing over 3,000rpm's at 65mph, and the truck feels like it needs another gear. I think I have also seen that there are many other options for transmissions, that can be used directly, or adapted for use with my 7.3 idi engine. This is a under $1,500 purchase, part time use (after I get my other car fixed), working truck, for trips to Home Depot, Lowes and the dump, so I don't want to spend thousands of dollars on a new or rebuilt transmission, unless absolutely necessary.

All suggestions will be helpful, specially how do I identify which transmission is currently inside my truck, and what are good options for replacement transmissions? Can I expect to stop all oil/fluid leaks in this old of a truck, without needing to rebuild everything?

This is my first ever Ford product, and first ever diesel engine vehicle, but I do have a small amount of mechanical abilities and since I am retired and on a small fixed income, I have much more time than money.

Thanks in advance for any answers.

 

[AmigaDave]

Some of you probably realized that I repeated myself quite a bit from my post in the "Introductions" forum, but I figured that not everyone reads all the new introduction threads, and I'm getting older, so "Yes", I do repeat myself from time to time.

2nd question but related to this thread, what alternative transmission options have people tried, connected to their 6.9L or 7.3L idi diesel motors? Has anyone tried to mate their idi to a modern 5, 6, 7, or 8 speed transmission? Are there any companies making adapter housings to fit different transmissions to the old idi engines?

Sure would be great to have 5+ forward gears to improve fuel mileage and uphill towing gear choices.

I'm also pretty sure that I'm NOT the first person to ask this question, so now I'll go do some more digging to see what answers I can find. What do the rest of you think (or know)?

 

[IDIoit]

I have a 2wd ZF5 manual transmission that I could part with..

 

[franklin2]

Click on this link, it shows the patterns and bolt numbers for the different transmissions.

http://www.lmctruck.com/icatalog/fd/full.aspx?Page=9

You really only have two possibilities; You either have a c6 which needs a little tweaking, or a very sick E4OD.

 

[austin92]

Your current transmission is probably a c6. I think the e4od started in 89-90. The c6 does not have an overdrive. You should take that offer of IDIot's. I have a zf5 in my truck and love it. Or you could stay auto and put a e4od in but you would have to mess with all the electronics. Only thing I can really suggest for the leaks is I've used Lucas trans fix on 2 vehicles, it stopped the leak on one of them. If it's the output shaft seal, those are very simple to change.

Here is a picture of a c6

You must be registered for see images attach

Here's a e4od

You must be registered for see images attach

http://www.grimmjeeper.com/gears.html

This^ website you can use to see what the transmission swap will do for your rpms. If you consider swapping rear end gears or changing tire size, that site is very helpful

https://www.gearvendors.com/

This^ site sells auxiliary overdrive units. They are pretty pricey but everyone that has one says they love it



Sent from my iPhone using Tapatalk

 

[UMR_Engnr]

I don't think the e4od was offered until 1989. One way to tell would be to look on the side of the injection pump and see if you have a vacuum regulator valve (c6) (there will be vacuum lines coming off), or an electronic throttle position sensor (e4od)(there will be an electrical connector and wires coming off). The C6 is mechanically controlled using vacuum and shift linkages, whereas the e4od is electronically controlled. In order to retrofit an e4od you need to add the electronic controls, which usually involves buying an external transmission computer. Early e4od's had some issues, so you need to make sure it is rebuilt to late 90s specs.

Other than an e4od swap or ZF-5 swap, people will add an auxilliary overdrive, such as Gear Vendors or a US Gear/DNE2 unit.

The vacuum regulator valve helps control the shift points, and if it is out of adjustment (or not working) then shifts can be very hard. My truck had this problem. I replaced and adjusted the valve and then the shifts were good to go. There are several links online for testing and adjusting the valve.

 

[MtnHaul]

Just a guess here but that leak of yours sounds like it could be a leaky rear main seal.

 

[franklin2]

car-part shows 88 was c6 only, 89, 90 could be c6 or e4OD, 91 is e4OD only. They show the c6 still available for the 460 and the 351w in 91.

 

[snicklas]

One easy way to tell if it's a C-6 or and E4OD.

In the bricknose trucks (87-91) if it is a C-6 Truck, it will have the normal column shift with the P RND21 indication under the speedometer.

On the E4OD equipped bricknose trucks, between the steering column and the Wait To Start/Water In Fuel light cluster will be a rocker switch that is the Overdrive On/Off switch.... the C-6 will not have this button.

This is the switch I am referring to:

Here you can see it peeking out behind the steering wheel:

You must be registered for see images

Here is just the bezel with switch installed:

You must be registered for see images attach

Just the switch:

You must be registered for see images attach

That is one of the quickest ways to tell.... 92+ is when the OD OFF button later the TOW/HAUL button moved to the end of the column shifter.

 

[IDIBRONCO]

If it's not going to be your daily driver, I say just fix the shifting problem since you're on a fixed income. It won't be perfect, but what really is?