When Should An EOD4 Shift Into OD

[YachtTech82]

It seems the truck won't Shift Into OD when it should. We have a 45mph speed limit all over our island and while cruising around the RPMs are resting around 2000 at 45 and to get it to go into OD I either need to let off the throttle almost all the way or speed up to about 55 then it will Shift Into OD. The truck has 35 inch tires which I would think would lower RPM at 45 and it also has 3:55 gears. How should this transmission be acting?

 

[DirtyWood]

Has your speedo been re-calibrated for the larger tires? What year truck? Before '92 you have to change a gear connected to the VSS--on a 4x4 it's on the driver side of the t-case, not sure about 2wd. Those RPMs don't quite add up--3.55 with 35" tires and 1.00:1 ratio in 3rd gear equals 1534 RPMs. Any chance your tach is off? Have you tested the resistance across the tach sensor leads? Should be 2k-3k Ohms, a new sensor is about 2400 Ohms.

 

[IDIBOBS]

Yea your tires with the 35s are really messing with your trans. It’s hurting it in many ways. This is just one you see. Your gears should be 4.56 or even 4.88. Your torque converter is not happy. Your clutches are not happy. The E4od is weak enough without lugging it around like this.

Gears NEED to be changed when tire size is increased. For every jump is tire size with out doing gears it’s like towing a 2500lb trailer. So you’re at 2 tire sizes up so it’s like you’re towing 5k. Remember when these trucks came out it was in the manual not to ever tow or haul with od on. The 4th gear can not pump enough fluid to keep things cool.

 

[YachtTech82]

Dang. I didn't realize a 35 inch tire would do so much. It's not that much taller than stock. As far as I know the tach is correct but I have not tested it. Is there a source for speedo gear replacements? I also just noticed the tyranny oil is down past the fill mark so that's not helping anything, will refill today and test. This is all my son's words and I haven't had a chance to drive it yet and confirm.

 

[raydav]

The simple answer to "when should an E4OD shift into OD", Is, whenever the controller tells it to. And that leads to the question, at any given moment, what is the controller telling the trans?

For well over a decade, I have found knowing what the controller is telling the trans to be very useful. Even directing side-of-the-road maintenance. It is also useful after tire or gear changes.

I put LEDs on each of the four solenoids. The solenoids are powered from inside the valve body, and activated by grounding the other side of the coil. So I connect an LED from the activation terminal to ground. When the coil is not activated, there is enough current thru the coil to light the LED, but not move the valve. When the coil is activated, the input to the LED is grounded, and so does not light.

If an LED is on, you know the coil is powered and intact, and that it is not activated. If the LED was on and is now off, you know the coil is now activated.

Knowing what light combination resulted in which gear selection, made me aware that the powe-off trans condition, in an E4OD, is forth gear and no converter lock. So, when I had a total electric power loss, I was able to jump the IP valve and starter, and drive home.

 

[u2slow]

I used to drive an IDI/5spd/3.54 truck regularly. OD saw very sparse use. Basically the 4-lane highways only.

Now with 35" tires, OD would be for some very fast driving.

 

[IDIBOBS]

Dang. I didn't realize a 35 inch tire would do so much. It's not that much taller than stock. As far as I know the tach is correct but I have not tested it. Is there a source for speedo gear replacements? I also just noticed the tyranny oil is down past the fill mark so that's not helping anything, will refill today and test. This is all my son's words and I haven't had a chance to drive it yet and confirm.

Stock tires are 30s so it’s a huge difference. I’ve been building race trucks, rock crawlers, trail jeeps and tow rigs my whole life. If you think about it a stock tow package surly with 4.10s had 30” tires so extrapolating that out u should be between 4.56 and 4.88 with 35s. It’s a massive difference. And you have the 3.55 so you’re even worse off already. All trucks/cars are under geared since smog,milage standards were Introduced. Gears multiply torque to the wheels and are the best thing any one can do to put power to the ground. Bigger tires are torque dividers. They take away torque.

 

[DirtyWood]

Stock tire should be a 235/85/16 which is 31.5" On an N/A truck with 4.10s I went from a stock 31.5 to 33 and it made a noticeable difference, but mostly on hills. I do recall the late Towcat writing in a post that the key to N/A 6.9/7.3 IDIs was in the axle gearing and that numerically higher gears were often advantageous even without increasing tire size. HP doesn't increase much until the RPMs are a bit over 2k and the deep gears help you get going from a stop or to keep a steady pace uphill with a load. My current truck has 3.55 because I do more long highway trips with it but I do miss the 4.10s on every big hill.
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I think new speedo gears are available from many places. Summit, Bronco Graveyard, probably Jegs too

 

[YachtTech82]

Well it was 2 qts low on atf, pan needs to be resealed and we have a cooler line dripping, he's out driving right now and will report back, I don't expect much to change based on what you guys have said about gearing.

 

[IDIBOBS]

Stock tire should be a 235/85/16 which is 31.5" On an N/A truck with 4.10s I went from a stock 31.5 to 33 and it made a noticeable difference, but mostly on hills. I do recall the late Towcat writing in a post that the key to N/A 6.9/7.3 IDIs was in the axle gearing and that numerically higher gears were often advantageous even without increasing tire size. HP doesn't increase much until the RPMs are a bit over 2k and the deep gears help you get going from a stop or to keep a steady pace uphill with a load. My current truck has 3.55 because I do more long highway trips with it but I do miss the 4.10s on every big hill.
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I think new speedo gears are available from many places. Summit, Bronco Graveyard, probably Jegs too

Many trucks came with 215/85/16. Even smaller. It’s not that it’s just these trucks. It’s all trucks can benifit from lower gears. Heck even cars. Autos and manuals. Even just one gear drop can actually help milage because you can upshift faster, the trans can lock (clutch engage) earlier and stay in the higher gear longer before down shifting. Autos run cooler and last longer. Clutches get less slip and last longer. Those that still drive these trucks at 55mph, the speed limit In most states in the 80s and 90s will never see a drop in mpgs at highway speeds and will always see a gain in mpgs in the city, towing, hills, hauling ect. The vast vast majority of people will benefit from lower gears. How much lower depends on your intended use and tire size.

 

[DirtyWood]

Stock tire should be a 235/85/16 which is 31.5

Many trucks came with 215/85/16. Even smaller. It’s not that it’s just these trucks. It’s all trucks can benifit from lower gears. Heck even cars. Autos and manuals. Even just one gear drop can actually help milage because you can upshift faster, the trans can lock (clutch engage) earlier and stay in the higher gear longer before down shifting. Autos run cooler and last longer. Clutches get less slip and last longer. Those that still drive these trucks at 55mph, the speed limit In most states in the 80s and 90s will never see a drop in mpgs at highway speeds and will always see a gain in mpgs in the city, towing, hills, hauling ect. The vast vast majority of people will benefit from lower gears. How much lower depends on your intended use and tire size.

I was assuming the OP's truck was 4x4 and every 4x4 F250/F350 I've seen had a 235/85/16, but I could be wrong. Driving at 55mph is okay sometimes but on a long highway run it sure is nice to hit 75 or 80 without bumping up against the governor. I guess that's why some would argue for a Gear Vendors unit with 4.10s or so.

 

[YachtTech82]

Yes truck IS 4x4.

 

[Ole BlackBetty]

Stock tire should be a 235/85/16 which is 31.5

I was assuming the OP's truck was 4x4 and every 4x4 F250/F350 I've seen had a 235/85/16, but I could be wrong. Driving at 55mph is okay sometimes but on a long highway run it sure is nice to hit 75 or 80 without bumping up against the governor. I guess that's why some would argue for a Gear Vendors unit with 4.10s or so.

mine is 4x4 and factory tires size is 215/85/16 1994 F350 Dually 4x4

 

[Black dawg]

mine is 4x4 and factory tires size is 215/85/16 1994 F350 Dually 4x4

Very common on dually stuff.

 

[IDIBOBS]

Stock tire should be a 235/85/16 which is 31.5

I was assuming the OP's truck was 4x4 and every 4x4 F250/F350 I've seen had a 235/85/16, but I could be wrong. Driving at 55mph is okay sometimes but on a long highway run it sure is nice to hit 75 or 80 without bumping up against the governor. I guess that's why some would argue for a Gear Vendors unit with 4.10s or so.

75-80? I don’t even drive my 68 Camaro or my Subaru wrx at 75-80mph. I’d never in a million years drive a 35+ year old 1ton truck at 75+. And people wonder why I get 25mpg. Slow down. It doesn’t really make up any real time and costs wear and tear, fuel and a wreck will be 10xs worse. In this particular case from the original post the island speed limit is 55. 55pmh with 35” tires is going to be very hard to do in OD. That’s the point of the post. Gotta turn OD off, get small tires or deeper gears. 4.56, or 4.88 is the correct gear sets for 35s.
I’d encourage everyone to look up gear and tire size charts and see original RPMS and how gears and tires effect RPMS.