transmission options

[Boomer II]

I've got a 97 5 speed, if you had your druthers would you swap to a 6 speed or go the gear vendors route?

 

[DHatfield]

Boomer I would probably opt for the gear vendors route since that would give you twice as many gears to chose from.

 

[pdolan]

You may get twice as many gears, but only two of them will be of any use. With the NV4500, 5th is about 0. 74, whereas with GV, 4rth OD is 0. 78, which is, for all intents and purpose, the same thing. Not only is there little point or need to split 1,2,3, but you will find that the lower gears exceed the GVs torque capacity. 3 direct is about 1. 67, so the 0. 78 OD gives a nice 1. 30 for 3 OD, and then 4 direct is 1. 0. NOW is where you need to be able to split, since the jump to 5th is 0. 74 which is quite a big rev drop when you are climbing a big grade at high weight, but using the GV your only choice is 0. 78 which is, as I said, no different.



The situation for the NV 5600 is even worse. 3,4,5 and 6 are very nicely spaced for a 6 speed, but in each case, the step is way too close to the GV ratio. 3rd is 2. 04, 3OD will be 1. 59, way too close to 4 direct at 1. 59. Same situation 4-5, 4 OD is 1. 08, almost bang on 5th direct at 1. 00, 5 OD becomes 0. 78, again nearly the same thing as 6th at 0. 73. So, in a 6 speed, you only gain an overdrive ratio above top.



Of the aux boxes that were around, only Michell Manufacturing offered a selection of ratios, and I can no longer find them. Both Gear Vendors and US Gear have ratios that are (were) perfectly suited to the 4 speed boxes that Doug Nash (USG) and Laycock de Normanville (GV) were trying to accomodate 20 years ago.



Today, almost everything uses 0. 7 and a bit for their OD ratio, both standard and automatic, so none of these boxes will actually "split" a gear. If you are a heavy hauler, you will know exactly what I mean.



If anyone is interested, a friend of mine has managed to get an agreement from USG to cut a batch of gearsets of 0. 8555 ratio for the dual range aux trans. This thing is rated for 35,000 lbs. of towing - nothing else in production will come anywhere near that (I am licensed for 36k). This ratio is chosen to exactly split the average late model 6 speed or automatic from direct to overdrive right smack in the middle. There was a pile of fancy engineering to do this, so send me an e-mail and I can get some details to you if you are interested.



Pat Dolan

 

[Boomer II]

Pat, I sent you a PM.

 

[Forrest]

I'd say neither.



The 6 speed just cuts down that big gap, but so does a bigger plate.

 

[bpete]

Go to the thread in this forum "How will my truck tow this" read what I was pulling with a tst 11 camplate. I was shifting at 2300rpms in the flat and 2600 on a hill and could pull every gear out.



I feel that unless you do ALOT of towing that these "splitters" may not pay for themselves. The splitter pat describes sounds very interesting though. LOL

Brant