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Discussion Starter #1
Hi, I have a 00 F350 7.3 ZF-6 dually 4X4 that won't go into 4 low. It lights up 4 Low and 4x4 lights on dash before starting. It goes into 4 High and 2WD fine. Just refuses to go into 4 low. Replaced transfer case motor, selector switch, brake position switch, checked all fuses, relays click when shifting to 4 high and back to 2WD. Shift to 4 low and it stays in high. Clutch position switch or GEM module? Everything else works fine. The PVH has been blocked off due to bad hub seals but that shouldn't prevent it from going into 4 low? This is my first ESOF and I would rather fix it myself as opposed to taking it somewhere. Thanks
 

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On my 99 dually 4x4 with automatic transmission when first got it was not use to how they work and it would not go into 4 low neither. Then found out it had to be in neutral and push on brakes for it to go in. Goes in just find now.
 

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Discussion Starter #3
I have tried it several times while working with it in neutral with the clutch and brakes both pushed down and it isn't doing any good. I ordered the clutch position switch for it and I am going to try that. If that doesn't work, I guess I have to pull the GEM module and check it for corrosion. The windshield might have let it get wet, but it has since been replaced (the windshield). Everything else works on the truck but 4 low. I may try locking hubs in and moving a little and trying again but the guy I got the truck from never got it to go in 4 low either. I plan on keeping the truck so I don't mind replacing a few parts but I hate the idea of trying to find someone to program the GEM module. If I can find the parts later on to change over to manual shift transfer case I might do that later. My 84 f250 always shifts into any range with no problems. I miss the simple way of doing things that doesn't break. Thanks
 

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Sounds like you have a bad relay. There are two relays for the shifting.
 

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Discussion Starter #5
Sbluke55, it might be. I bought one new relay and tried it if I remember right in both spots. I might get another new one and just put them both in and see what it does. I have done mechanic work all my life but never touched an ESOF before this truck. I really like the truck and plan to keep it so I am going to fix it what ever it is but if it is relays that would sure beat buying a GEM module. One other question, is the front axle a Dana 50 or a Dana 60? I always thought all F350 duallys had D60's in the front with D80's in the back, but I heard that some had D50's in the front.
 

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I believe the earlier trucks had d50 and the later ones had d60's. My guess is you have a d50.
 

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Discussion Starter #7
Ok, it probably won't matter much unless I need to replace parts in it. I will see about getting another relay tomorrow and put them both in, maybe that will take care of it. I have heard where the relays connect underneath corrode also, I might check that while I am at it. Thanks
 

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The 60 can be readily identified by its straight axle tubes, 10 bolt asymmetrical cover, and a "60" cast in to the housing. 50 is cast into the 50 ones.
 

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Discussion Starter #10
OK, I put two new relays in for the 4x4 shift and it makes no difference, still only goes to 2wd and 4 high. I did look under truck and "248" is cast in front axle center web. I understand this to mean I have a D60? Thanks
 

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Discussion Starter #11
I still haven't got the truck to go into 4 low. Waiting on clutch switch to come in. I changed rear pinion seal and yoke today. The yoke was letting u-joint slide back and forth between the clamps so installed new Spicer parts. I also started on installing gauges ( boost and egt ). Drilling the hole in the manifold for the EGT probe is not any fun but I have that done. All that is left is to finish wiring for lights to gauges. I need to get the fill plug out of transfer case to check the level, but it is very tight and wallowed a little where allen wrench goes. Any ideas? I thought maybe if it is low it might prevent the shift to 4low, but I kind of doubt it. Thanks
 

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Discussion Starter #12
I got my clutch position switch in the truck today, still no 4 low. Must be bad GEM module or broken or corroded wire/connection somewhere. The gauges are working great. I saw 900 on egt's and 24 on boost showering on it so I am happy. I like my hydra tuner while I am thinking of it. The guy I got the truck from said the electric windows and something else was acting up after a rain, I put a new windshield in and everything but 4 low works fine so I think it is GEM module time next. I still haven't got the fill plug out of transfer case, I will have to work on that later when I have more time.
Thanks to all!
 
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