I'm in the proccess of purchasing a gear splitter for my '79 F-350 4x4 supercab p/u.The truck has a NP 435 tranny (truck 4sp manuel w/ granny low 1st gear) and I would like to split the gears and get a overdrive for it. I'm looking at U S Gear and Gear Vendor. Pros and cons with either unit would be apreciated.I understand that with Gear Vendor's you have to be travelling 20 mph and use it in 2wd only. With U S Gear, is it noisey and can the shifting device standup to constant shifting (splitting gears)and is 20% enough reduction? Are there other units available that can stand up to 450-500 lb.of torque and 18,000 GCVW?(I've posted this also in the tranny forum).
Thanks in advance.Mike B.

 

I think the GV unit requires an adapter to mount the unit on the back of your transfercase. This is an additional cost, but I don't know how much. Their thinking is that if you are in 4X4 low range you probably won't need the overdrive and gearsplitting. They are probably correct. They have some type of electronic lockout to prevent you from using the auxillary overdrive if in 4X4 low range. I'm not sure about anything to do with 20 mph. I've not read that or heard it before. The U.S. gear unit requests that you move your transfer case back and it mounts between the transmission and transfer case. This requires custom alterations to the rear AND front driveshafts where the GV unit only requires modification to the rear. Both are heavy duty units. US Gear has a 20% reduction ratio and GV has 22%. Both claim shift on the fly from what I remember.
I'd strongly consider the GV unit because of the 22% OD. But you might want to look at your individual gear ratio's in every gear and see how much difference there is between OD in one gear and reg in the next higer gear. In my tranny, 5th gear reg is exactly the same as 4th gear OD with the one unit. I think there are charts on both websites to give those calculations based on your rear end ratio.
Good luck, you probably can't make a "wrong" decision here.
TonyG

 

teleMike, I like the looks of the GV unit better. My budget does not currently allow the purchase of either one, but if it did I would buy the planetary style from GV, they look stronger to me. GV says that they can't imagine why someone would need 4wd overdrive or splitting ability, but they are in California and don't understand what real weather can be like. In upper peninsula Michigan trucks are usually in 4 wheel drive from december thru march, towing or not. I think what you will need is to do some sweet talking to the GV guys. Some of their engineers understand things a whole lot better than some of their salesmen, who have probably never seen a snowflake in their life. You will need a unit for a 2 wd tranny, and have the GV built with what they call a 'parking brake' tail housing. The park brake tail has the correct pattern to go into the front of your T-case. So yes you can mount the GV between the trans and T-case, it just takes a little more work. I fear that their salesman are looking for the quickest, easiest commission rather than what a customer needs. Their early sales literature shows the unit in 4wd trucks between the trans and tcase. You will need new drive shafts front and back, and the unit will have to mounted so that the wieght of the T-case does not hang on the back of the splitter. Your shifter for your tcase may have to move as well. Maybe they recommend the behind the tcase mount just because it is easy. If I had the money to buy one, I would mount it in the middle. DF

 

>Their thinking is that if you
>are in 4X4 low range you probably won't need the overdrive
>and gearsplitting. They are probably correct. They have
>some type of electronic lockout to prevent you from using
>the auxillary overdrive if in 4X4 low range.

This should read 4X4(period)not 4x4 low range. Their lockout prevents the overdrive from being used if your in 4X4. It seems like GV views their units as primarily beneficial for Overdrive in high gear. Yes, when in 4X4 people seldom have the need to travel over 45-50, although I've been in 4X4 doing 60+ in an light snow. 1-2". But you can always use the gear splitting if pulling a load or just to find your right gear in 4X4. Like dinofan says, you'll probably have to talk with them to see if they can disable the electronic lockout.

There might be some discussion group somewhere for those guys who tow camper trailers around the country. Some of those guys run GV or US Gear units.

A fellow in my area says that various farm trucks (potato,beet,cabbage trucks) have or had 3speed spicer auxillary trans. They had an ultra low for working in the fields, regular range for loaded on the road and a high range for coming back from the processing plant or whatever. They probably had 5.56 gears or something in the rear. He had put one in a diesel pickup that he had and got really great fuel mileage. (27?) He says they were synchro to shift on the fly too. I think he has a couple used ones to sell somewhere in the <$1000 range, but it's been awhile since I talked with him. Something to keep a lookout for.
TonyG