gear vendors testing

[burt]

Hey guys, just got a p type gear vendors off of ebay. Its one for a 4x4 with a bw 1356 adapter so it should be about perfect since both my trucks fit those parameters. The seller gave a 14 day return policy so i want to test it asap. I won't be able to get a permenent install done in the alloted amount of time due to minor parts gathering i need to do to get it just right but want to confirm it works before time is up. I can't really get the electronics set up right with the parts I have so my question is can I run a 12v hot from a toggle switch in the cab to one blade on the solenoid and a ground to the other blade on the solenoid and switch the toggle switch when im going 30+ mph to see if it works right? I know I need to be going fast enough and not in reverse or 4x4 ect but is this all that needs to be done to check its function. I belive I can get it installed well enough to use with parts I have tomorrow but doing it right is going to take a little longer than I have. Two trucks are 1) 1990 f350 4x4 zf5 reg cab long bed 2) 1993 f350 4x4 zf5 cclb, man I need to create a sig so I dont have to say that every time

 

[burt]

Or how bout for starters while I have no driveshaft on there hook a jumper box to the two blades of the solenoid, start the truck and put it into 5th and let out the clutch. Then turn the jumper box off and on and see if that seems to go well? Would that be spinning fast enough at idle to be able to properly engage the gv?

 

[towcat]

i have a newsflash for you .
a gv has an oil pump and the oil pump needs to be going at a minimum of 45 mph shaft speed to work properly. if you engage it above 45mph, I "should" work properly or there was a serious mistake.

 

[burt]

It's a minimum 45 mph? Why does everything say it splits 2nd then? Wouldn't that depend on your diff gear ratio? Would 5th at idle with no driveshaft not be spinning fast enough?

 

[towcat]

It's a minimum 45 mph? Why does everything say it splits 2nd then? Wouldn't that depend on your diff gear ratio? Would 5th at idle with no driveshaft not be spinning fast enough?

note I said shaft speed. whatever engine rpm is at 45mph is where you need to be to work properly. the pump is literally a piston pump. it has to be going fast enough at whatever speed to build up enough pressure.

 

[Black dawg]

Or how bout for starters while I have no driveshaft on there hook a jumper box to the two blades of the solenoid, start the truck and put it into 5th and let out the clutch. Then turn the jumper box off and on and see if that seems to go well? Would that be spinning fast enough at idle to be able to properly engage the gv?

To properly test the gv, you want a driveshaft, there are many different ways they can fail. I think gear vendors says it will engage at 20-25, but there is about a 4 sec delay. It will actually engage at half that speed, but the line of having enough pressure to not slip it becomes fuzzy.

 

[burt]

The no drive shaft idea was just for that moment so I could see if it would even engage with 12v hooked directly up to the solenoid while I was laying under the truck. So since then I have been reading as much as possible and then decided to go with a fused switch in the cab going 12v directly to one blade on solenoid and neg directly to the other blade. Despite everything else I read including black dawgs recent post I tested it with a gps telling me that I was going over 45 mph as per tow cats news flash. It seems to work fine so far in my quick test drive. I probably only drove about 15 miles and it seems rather hot to the touch (little hotter than t case anyway). Besides that shifts quickly and smoothly with the right rpm or clutch combo and doesn't make any funny sounds. So now that another long term member is saying 25 mph is a conservative shifting speed, why (tow cat) should I make sure I'm going 45. I read that you are very experienced with these units so I'm very curious about the conflicting info. I'm reving pretty hard in third to get to 45mph so that minimum speed is pretty limiting for me gear splitting. Thanks for the responses

 

[jaluhn83]

Honestly, no way to know anything short of actually hooking it fully up and load testing in while driving.... even if it shifts fine the clutch might slip, bearings be bad, etc etc and there' no way to know until you're actually driving with it.

I'd see if the oil look ok (not burnt or watery) and that's about all you can really do.

The reason for the shift speed restriction lies in the design of the system, and there really is no hard and fast answer.

The Gear Vendors OD is based on a British unit built by Laylock (IIRC) that was originally used as an add on overdrive gear for 60's sports cars to help out on top end. It was designed to be used solely as a 5th gear under high speed conditions. Volvos actually used them all the way up to the mid 80s in all of their manual cars. Consequently, the main concern was a robust functional easy and smooth shifting light duty unit. At the time medium & heavy duty trucks would use a brownie box or a 2 speed rear end for additional gearing.

Subsequently, the heavier duty version of the Laylock ('P type') was adapted by GV for truck use. The early GV units are as I understand identical to the Laylock units, but later ones have some upgrades for durability. However, it's still a system designed for low to moderate load, high speed and smooth shifting - not heavy duty low speed towing use or splitting gears.

Where you really have an issue if the shift system. The internal design uses a overdrive planetary gearset with a cone clutch connected to the planet carrier and having facings on both sides. It's held with the inner surface against the ring gear assembly by spring pressure for direct drive, and shifted hydraulically forward to wear the outer surface bears on the inside of the case to hold the planet carrier stationary and engage the overdrive gear. The hydraulic pressure to do this is supplied by an input shaft driven hydraulic pump. The solenoid controls a valve that allows the pump to build pressure and shift the clutch.

Thus, the pressure holding the clutch in the overdrive position against the substantial spring pressure comes from the input driven pump - the slower you're going the less flow you're going to get from the pump, at some point becoming low enough that you start to loose pressure. What speed this actually is is hard to say as it depends on how much internal leakage there is, thickness of the fluid, etc. Further, less pump volume means the shifts will be slower, resulting in more time that the clutch is slipping in both gears.

So, if you're running in OD at too low of speed, particularly under high load (and remember the trans output torque increases substantially in lower gears for the same engine output) you run the risk of getting clutch slippage in the GV box... and as a side effect, as it gets hot from friction the fluid thins out and it will leak more, causing lower pressure all things being equal. Given how expensive that clutch is to repair, this isn't something I'd want to do.

Now, I personally have never owned a GV unit, and plenty of folks have lots of good experience with them... so take what I say with a grain of salt. However, to me personally, I would consider the GV unit as a additional top gear only - use it like the 'od' button on an E4OD - good for highway cruising but not really for towing.

 

[burt]

Thank you for taking the time to write that all out. Sure paints a different picture than gear vendors does. I'm still very curious about the discrepancy between 45 mph and ~20mph being the magic # for shifting. I understand the faster the shaft speed the higher the pressure (I have read carefully the responses) but at what speed is sufficient I'm still not confident on. Tow cat being regarded as one of the most experienced gv users here is the only person that I have found anywhere that says 45 is the minimum. Most say around 20. I would just take his word for it if I wasn't so motivated to have the speed be lower. Just to clarify I'm not trying to argue in the least just motivated to learn. I'd rather take advise from people that work these trucks like I do than the company itself.

 

[jaluhn83]

I would say around 45. As I said, the system is not designed for any low speed use. Would you use 5th on a manual trans at 20 mph? Same philosophy.

At the end of the day it depends on how brave you feel. I think it's likely that you can go all the way down to 20-30 mph and be fine. But I personally wouldn't. To me the GV unit is vastly over marketed - it's very good at doing what it's designed for, which is an semi automatic overdrive gear for highway cruising. That's not the same as splitting gears or low speed slugging uphill. Sort of like using an explorer to pull a 7k trailer.... can it be done? Yes. Will it do it well? Questionable.....

 

[Agnem]

I've got two gear vendors units in two trucks, and I can tell you that the image painted by jaluhn83 sounds like it was written by one of US Gear's sales reps. I don't dispute the description of the technology, but there is a lot of hyperbole in what it makes you believe. First of all, the speed at which you can shift, will vary depending on what rear axle ratio you have. In the Moose Truck, with 37" tires and a 3.55 rear, I pretty much need to be doing 23 MPH in order to get it to engage. Yes, there is a "delay" as hydraulic pressure builds, but when it engages, you better have the clutch pushed in, or your going to bang your head on the rear window. I count to 7, push... 8, let out on 9, and I can shift as smooth as any manual trans gear. Above 32 MPH, it's much easier. count to 3, push, 4, let out on 5 and it's good. Above 40 and it's instantaneous. I'm not going to debate the durability. I'm sure people have blown them up, but then people have blown up pretty much everything. Mine have been completely trouble free and have done all I have asked them to do. The Moose Truck has had the same one under it since 1997. It's never been out, and all I do is change the oil in it. It's mounted to the BW1345. The Lady Moose runs a divorced unit I got second hand. The front shaft seal has a slow leak, and always has. It's been that way since 2004, and pulls 16,000 pounds regularly. Both units will "bang" pretty hard if you fail to get the clutch pushed in at the right moment. It's enough to make you think the driveshaft is going to twist. This tells me the friction clutches are working just fine. The "computer" unit keeps you out of trouble. Mostly, by disengaging the clutches before hydraulic pressure gets too low due to you forgetting to downshift. I love both of mine, and if I could afford it, I'd equip all my rigs with one. i have 7 forward gears with the Moose Truck, and 9 with the Lady Moose. Yes, it is a fine gear splitter, and will do any gear fast enough to give you pressure without question.

 

[burt]

Thanks Mel for your post. I appreciate the content because I trust it and it tells me what I'm trying to hear. I see that on the bottom of the unit there is two treaded holes that appear to be for bolting it to a crossmember. Have any of you guys made a cross member for it to bolt to? I'm gonna build something of a skid for it. It looks like if you took a hit to it it could be catastrophic. Also, anybody have an opinion on slip yolk vs slip splined driveshaft on these. Unit came with a fixed yolk and since I have to get driveline work done regardless I'm not sure if I should switch to slip yolk or leave the yolk and get a slip splined shaft made. Thanks again for reading and posting guys

 

[Agnem]

The manual specifically states NOT to try and support the unit in any way. Mine's been hanging way out there unsupported for 17 years, and works just fine. I know it seems crazy having all that weight hanging out behind the original transmission, but that's the way they work.

 

[burt]

Oh ok cool. Then I'll just make a plate to protect it but not contact it. That will be easier anyway. Sure does seem vulnerable hanging out there. Thanks

 

[Black dawg]

Gear vendor says 20mph. from my experience 20 is WAY safe under power.