Introduction and Gear Vendors Issue

EasyRider01

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Hello everyone,
My name is Dustin and I just purchased a 1987 F350 Crew Cab Long Bed Dually with 6.9 diesel and c6 tranny with gear vendors overdrive. This is my first diesel and Ford so I'm a total newb with both. Purchased the truck in Nashville with the gear vendors overdrive not working and drove it home, close to Topeka, Kansas, at 55mph the entire way to conserve fuel. That was a LONG trip! I'd like to get the overdrive working again.

When I drove it home the electronics for the gear vendors overdrive were not working at all. Upon arriving at home I inspected everything and discovered that a fuse was blown and one wire to the solenoid was damaged. Replaced the fuse and repaired the wiring at the solenoid and I had power to all the electronics. Took a test drive and overdrive did not engage, upon slowing down at about 20mph the rear end shuttered like it was locked up or something so I immediately shut down the overdrive and all was well again.

I searched high and low through the posts here and learned quite a bit on how it works and what to test. I believe my solenoid is not engaging and I discovered the o'rings on the solenoid are also shot. I removed the solenoid and hooked it straight up to a good working 12 volt battery and no click whatsoever. I'd like to know where I can get another solenoid? I'm not sure how I can identify whether I have the "J" series or the "P" series unit? Is there anything else I should test before ordering the solenoid? I'm pretty mechanically inclined and am not afraid to rebuild the unit if I need to.

I will have a lot more questions on the truck but I'd like to keep the posts/replies simple and each to their own topic. You all seem to be pretty well informed on this subject. Thanks in advance for any and all replies.
 

icanfixall

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Welcome to the forum. I suggest calling Gear Vendors for help because they are great over the phone really. Be sure to tell them the numbers on the serial number plate too. That way they will know everything about your unit. Easy way to know if you have the early "J" or later "P" model is look at the speedo cable housing in the gv. If its small about 1 inch diameter its the J because the P is about 2 inch diameter.
 

FarmerFrank

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I'd suggest removing the unit, selling it to me for about nothing and ill send ya a regular tail shaft.

You get that thing working and you'll never consider selling it and wonder how you ever drove the truck without it working.

Good luck with the ol girl
 

typ4

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Did you by chance check the oil level? Also ATF is an acceptable test oil till the bugs are worked out, if the o rings are bad on the solenoid it may have not built pressure and the cone clutch could be bad, drain unit, reseal solenoid, fill and test, I am not sure if they actually click, the valve inside is tiny.
 

EasyRider01

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I'd really rather try not to call gear vendors if possible. I'm hard of hearing and I have to use a video relay system with a sign language interpreter to make phone calls. That can get to be a real pita when I start using technical terms that the interpreter may not understand.

Thanks Farmer Frank, I don't plan on giving it away. :sly I was missing the overdrive just 5 minutes onto the highway. :rotflmao

I didn't actually check the fluid levels yet, I was gonna just go ahead and change the fluids out. I can see the fluid is pretty dang dark so don't think it had been changed for a long time. That's not good... Thanks for the atf tip, that will save me a little money. Ill get some orings today and install the solenoid. Looking more likely that I'll need to do a rebuild.
 

sjwelds

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Hey just curious where in KS are you located? Always nice to see another IDI owner in the same state! Looks like a decent truck. Welcome to the forum.
 

icanfixall

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These units need hydraulic pressure to operate. This is why you need to be rolling around 20 mph before they build enough pressure to work the cone clutch. As for actually talking to Gear Vendors you can email them and explain you are not able to talk on the knone too. Just make sure you have the numbers off the plate so they know what trans you have. These gv units are very nice units and they work very hard for years. We have seen some that have broken up so bad they split the case and parts fell out on the road too. That is not the norm for sure either. GV can rebuild the J or P types. A few years ago they bought the company in England that was building these units so now they do all the making of parts in house. These overdrives have been found in Austin Healeys, Triumphs and Volvo cars since the mid 50's.
 

Black dawg

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Never tested the sol out of the unit, but when it is put together, there is a definite click kinda noise. the problems I have seen with them is usually the crappy electronics that come with them, and low/no fluid. Also, my experience with one behind a c6 is that it can be pretty smooth engaging (can be hard to notice). The shuddering on decel tells me that it was/was trying to engage.

after thinking about I dont remember if it made a noise you could hear, but it you had your hand on the sol, you could feel a light thump inside.
 
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EasyRider01

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Sherwin, I am located in a very small town, Vassar. It is practically right next to Pomona Lake. I'll only be here for a few more months then will be relocating over to Springfield, Mo.

Icanfixall, thanks for that information. I'll be sure to email them if I can't get the unit working.

I wasn't able to get all the o'rings I needed, they'll be here in about a week or so, so any testing going forward is put on hold til then. I'll recheck the solenoid clicking with it installed on the unit as soon as the o'rings come in. Will report my findings.
 

Black dawg

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Forgot to add, use a good fitting, sharp socket to check the fluid. The plugs have to be the easiest on the planet to round off.
 

crashnzuk

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Seems to me it must have been engaged (to some degree) if it clunked/shuddered on decel at 20 mph. 20 mph is the cut-off for these things working and they do clunk/shudder/thud when switched off. Hopefully it's an easy fix, but I'm betting it's worn out.
Travis..
 

Agnem

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Best way to troubleshoot these things is a pair of jackstands, and take your wheels off. Make sure the unit is full of fluid. Make a barber poll stripe with some yellow tape on the driveshaft (the best visual indication that the shaft starts spinning faster when it shifts up). Have a way to apply 12 volts directly to the solenoid. As long as your speedometer shows 20 MPH, when you apply the voltage, the unit should clunk and your drive shaft should speed up. Remove the voltage and "clunk" your drive shaft should slow down. If it does this, then your problem is the electronics, which would include the speed sensor, and electronic box, any switches and associated wiring. Don't allow the input speed to drop below 15 or you may start to slip the clutches due to low hydraulic pressure.
 

EasyRider01

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Thank you everyone. At the very least, I am headed in the right direction in getting the overdrive diagnosed. Unfortunately, I just discovered what I think is a head gasket leak (I have another thread on this issue). Kinda short on money and have a 3 week vacation coming up so will not get back to trying to repair the overdrive until I return from vacation and get the head gasket replaced. I'll revive this thread as soon as that time comes.
 

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