Hello,

After I got my truck back (it was stolen) I did a bunch of work to it. I feel like I have done a bunch of mods to it but the towing performance doesn't seem that great. It is my first large truck so I don't have a lot to compare it to. I need your help.

It has 167k miles, the transmission shifts well and doesn't hunt for gears. I have 3.73 gears and stock size tires. The tach reads 2k when I am doing 70 mph. I have autometer boost and egt gauges. I know the brakes are good and calipers aren't hanging up. I had the exhaust manifolds machined, added manifold gaskets, and put on bellowed up pipes. I can't see any exhaust leaks. Its got a 4" down pipe, original turbo and injectors, hydro chip set on PHP 85 horsepower tow, banks inter cooler, and big riff raff air filter. It has a bit of blow by but nothing crazy and it consumes a quart and a half of oil between oil changes. The truck seems really fast and powerful up the hills until I tow.

I bought a 24' 4500# travel trailer in Utah this weekend and towed it back to Denver. I could tow in overdrive at 2k rpm on the flats and some light grades. On some mid range grades I had to turn off over drive and then be careful not to pass 1200 egts. On I70 going up Vail pass and Eisenhower pass I had to take it out of overdrive then downshift to 2 and do 40 mph. The boost pressure was about 10# sustained up the hills, it hit 12-13# sometimes, and went to 15# one time.

I unhooked the ebpv connector and I am going to out to make sure it is not stuck closed. If that doesn't help I am going to build a boost leak detector.

Should I be able to tow a trailer up steep grades without downshifting so far? Should I be expecting more out of my truck? Could someone who has a similar rig tell me results with towing capability and boost pressure?

Thanks,

Bill

 

How much boost does it make when you really get on it?

 

15# max

I just checked the epbv and it is not stuck.

The intercooler install is new. I retightened some connections.

I found some oil on the inter cooler pipes that connect to the turbo. I also found some oil in the valley. There was no oil in the valley before the intercooler install. I cleaned everything up and will check for oil again.

I am headed out to the highway to get on it and will report back some boost numbers.

 

After tightening the boots I had the truck making 18# of boost on the +85 hp setting. It was only making #15 at the most on the +85 setting when I was towing.

 

I have the 4:10 gears and on a really steep mountain grade I'll be down to 2nd gear at 40 mph. But I pull 17-18K across country. Sounds like you have done a lot of good mods so I think you should be doing better then you say. At 60 mph I'm at 2k rpm, I'm think you have 3:55's.

 

I'm with Glen on the 3.55s. Ford did not put 3.73s in the OBS, You couldn't get them until the Superduties. In my opinion,3.55s are not for towing heavy loads with these trucks.

 

You seem to be at decent elevation, N/A vehicles become super slugs up there... turbo stuff barely keeps up. These trucks lay out about 180rwhp/330rwtq stock, I have read about 200rwhp with full exhaust and intake. So you making 275rwhp, maybe, with that tune and full exhaust plus intake is barely what my stock 6.4 made. What you DO have on your side is significantly less curb weight. But with the 3.55:1 gears, unless you swapped to 3.73:1, and an oversized tired that hurts. It is not just the height, but the damned rotational mass of the thing trying to be turned.

If you need to know, I can ask my friend who was a former Chrysler engineer the math for power loss at certain elevations. It goes up something like X% per 1000m, sort of like wind drag increases exponentially as speed increases, as does power required to sustain speed. It is really neat stuff.

I am not sure what torque converter you are using in your E4OD, but when I went to a low stall in the 6.4 the difference was H U G E in how the truck towed big loads, putt-putted around, and how it hauled *** with the converter unlocked. Basically you will not be blowing through the converter and sitting at redline with your foot to the floor, you actually make use of the torque the engine creates. I am not sure how to really explain it. If my old phone and truck did not die, I could post a full throttle run with a low stall converter for you to see the difference. I guess maybe it is more like driving the thing with the converter locked always or how a five speed truck drives.

 

When I bought my 2 car gooseneck the dry weight was 4200 pounds. My truck was a slug towing that with a 6 position chip in any mode.

After stage one injectors she towed easy but heated up quickly. After the water meth I could haul 2 cars on the trailer just fine, and dropping down to 3rd or even second gear if I lost momentum on grades. My boost in tow mode usually does not go above 14 or 15 pounds. 25-30PSI in race mode.

Not sure if that helps with your comparison, but if you're at elevation, and mostly stock, then it may be right on especially with 3:55 gears.

 

A) you won't see 85hp from stock injectors.
b) if you are lucky you might he putting 180hp to the tires.
C) if you check fuel pressure on a hard long pull I guarantee it's very low.

In my opinion the 3.55 aren't helping tho very nice to drive unloaded.

​​​​​

 

 

Thanks for the replies.

I have axle code 39. 3.55 gears. I will only be towing the small camper. Once I get this boost/ power issue settled they will be ok for me.

I forgot to mention I have an electric fuel system and autometer fuel pressure gauge in the truck. The pressure is set at 65# and doesn't drop below 62# under load.

From here I will make a boost pressure gauge and check with soapy water for leaks.

I have been reading testing the performance with a scanner. Is that a good idea?

 

Oh, check the pedal voltage for WOT.

DVOM on the GY/W and GY/R wires. Key on, engine off.... at least 0.37V throttle closed/idle and no more than 4.5V at WOT. BRN/W is a constant 5V.

I still need to do this, just lazy.

 

ha, I can peg my egt gauge so I've been lazy too.

 

For like 10 years?!?!

What a slacker...

 

Who me? I guess I said it so there is no getting around it, lol.