I'm working on my 1990 E350. It has the 7.3 liter. The first issue is with the oil cooler. I have the typical o-ring leak and I have already removed the cooler. I got it unbolted and removed from the truck without having to lift the motor. I just removed the lower radiator hose so I could see and also the ground wire from the front of the block. It came down fairly easy,was just a matter of turning it at just the right time. Anyway I don't have a shop or garage with a high enough door to pull the truck in,need 11ft clearence,so I'm doing this in the street. I need some advice/info on the best way to remove the front and rear headers. The next issue I have is that this truck tops out at 55 mph. It has a c6 tranny and a dana 70 rearend with 4:10 gear ratio. I can get it upto 70 mph but the engine rpms sound really high at this speed, Ive only had the truck a month and have not gotten around to installing a tach yet so not sure exactly what the rpms are at 70mph but I know it's pushing the limit,To be honest even at 55mph it sound like the rpm are in the 3500-4000 rpm range. The gear selector reads L1,L2 and D. I know from experience that a C6 is just a 3 speed automatic and when pulling out from stop I can feel and hear it shift fine so I know it's not a tranny issue. I need this truck for work. I use it for towing and hauling(I just started a moving company) and I cannot begin to explain how much my family and I depend on this truck so I have to get this truck done right because I'm on the verge of having to cancel to moving contracts this week. Since I am considering swapping to a slighty higher gear ratio. I need power for towing and hauling but I also need a slightly better mpg ratio too so any suggestions would be great. For now my main focus is on the oil cooler repairs. I have a couple gallons of each of the following oils, Rotella,MotorCraft and Lucas. Which of the 3 would you use? I've already purchased Wix filters because Ive had bad experiences with Fram filters. Something I forgot to mention is that Ive also purchased a tranny filter kit since I don't know when it was last changed and even though I know better I was foolishly thinking it may somehow help with the speed issue. Wishful thinking lol I've also purchased a new air filter as well. I should mention that according to websits Ive used it's supposed to have the 4:10 gear ratio but I guess it might have been changed at some point? Well I guess I'll stop here and wait for some help with the oil cooler info first and then move on to the speed/rpm issue.

 

Welcome to the forum!

The headers will have to be tapped off with a rubber or plastic mallet. They're aluminum, so you can't go too hard on them or they will crack.

Here is a hard point that is safer to hit against:


(Credit Dieselcrawler on OBN for the photo)

Putting them back on will be fun too. I have a shop press but if you can get creative with a floor jack, that would work too. Use grease on the O rings before assembly and be very careful that the headers slip on straight and not crooked.

I feel your pain with the transmission/gearing issue. That was the same combo my truck came with from factory. Your max RPM is likely going to be around 3300 somewhere around 70 MPH depending on your tire diameter. My truck could just barely reach 75 before bumping the governor before I regreared it.

I'm also not sure what you will gain by swapping to a taller ratio. If you spend a lot of time in stop and go traffic inside the city, then you might be better off to leave things be. If however you spend alot of time cruising above 55, then regearing might help. However you should also bear in mind that you have a tall, heavy vehicle and you might gear yourself out of the ideal cruising speed considering the limited horsepower of the engine. I mention this because of your comment about lots of towing and heavy loads. Instead of trying to cruise at 70 MPH, you may simply be better off doing 55 (if its safely possible, I realize it isn't in many cases).

You don't have to worry about hurting it at 55 MPH though. You would be turning about 2500 RPM and these engines can run against the governor all day. You might get a headache from the noise, but the engine was designed for it.

As far as oil is concerned, I try and stay away from those discussions, but many guys swear by rotella. I've never used it so I can't fairly say one way or another.

 

I was able to push the cooler together a little bit by hand and then tap it together with a small soft faced hammer. Make sure you put the last pair of o-rings on the bundle to avoid cutting them when you slide it together. Oil is oil and any 15-40 will lube like the next, so don't get too worried there.

 

And if doing a fluid change on the trans make sure you drain the torque converter as that is where most of the old fluid is.

 

heres an rpm calculator if you want to figure out what rpm you're turning
Automotive Calculators offer to you by Ford Trucks Enthusiasts | www.ford-trucks.com
and heres one to igure your tire diamater
Automotive Calculators offer to you by Ford Trucks Enthusiasts | www.ford-trucks.com