when is a 5 x 4 not a 5 x 4 ?

[greywuuf]

kinda new to the " big" truck thing, driven a few 5 speeds with 2 speed axles, my unimog has a 5 speed and a 3 speed aux but never an air shift or a road ranger. I am looking to buy a particular truck in my area, and it has a 5 speed with a 4 speed brownie. I understand running one transmission into a second one, but I gather that is not how road rangers and such work. additionally when I google and you tube 5x4 transmission or twin stick ... I seem to come up with a lot more on the Big truck trannies and not so much on the "brownies"

So is my shift pattern just going to depend on what two transmissions I have and where the gear overlap occurs ?, or was there a "standard" pattern that chevy adhered to ? given the time and some way to turn the transmission ( like remove it from the engine) I could determine each individual gear ratio and work out the technically correct pattern, but I was hoping to not have to go to that extreme right away.

Dan in the frozen North

[mrolds88]

Dan, check out some videos on youtube by buckbz. He has a couple of videos of his trucks that are twin sticks. Might help you. Also if you get the info off of the tags on both trannies, I'm sure that you could find some info on the net somewhere.

[greywuuf]

I have seen his vids, nice 4-53stuff a gmc and a Diamond t, but I am unsure if he runs a "conventional twin stick 5x4 or a 5 with a 4 speed brownie ? also throws in a Jake which I will not have.

[C10 - C90 Bill]

Dan, most Twin Stick trucks will have the Shifting Sequence on a Tag on the door. In my opinion there is one pattern that is more common than the others, but there are many different ones out there. Like the one I checked out in Salem, VA for example. If you still have those pictures, check it out when you get a chance. I also posted the Pattern in typed-out form in one of the threads.

Bill

[greywuuf]

yeah I remember both the typed out and still have the pictures, what I don't know if that was a "twin stick" or a 5 and a brownie? I can understand that a made for each other bolted together unit would have gears that would work like a splitter range box, I don't know if a Brownie was spec'd out to be the same way or if it was just a haphazard throw another tranny on there and figure out where they fall kind of thing

[C10 - C90 Bill]

Dan, I believe that truck was all original with a GM provided Main Trans and Aux.

Also, if someone "put together" one, and the Shifting Pattern is not known, I guess there would be 2 reasonable ways to determine it. One would be to research the Tags on the Trans as mrolds has mentioned and figure it out on paper, or just guess at it and determine it by road testing it. That would be my preferred way, lol.

[greywuuf]

The truck I am looking at calls out a main and an aux on the glove box tag, but the doors have been replaced, and it would bother me to have random gear placement.....in my mind it should either be each gear on the main and all the aux, ie: 1,1: 1,2: 1,3: 1,4 2,1: 2,2 etc
or all the gears in the main, and shift "ranges" and repeat anything else just seems random

[C10 - C90 Bill]

By the way, with the Main and Aux Trans that I mentioned are the "more common" ones, when driven on the Road, you only use 13 of the Gears.

Bill

[63 & 64 Bowties]

Does this help you?

[C10 - C90 Bill]

The picture that Bill posted above is the one I took in Salem, VA. This is a very "un-common" example, lol. It actually was the first one I've ever seen. The "Pattern" is very typical of a 5 X 4, but the "Shifting Sequence "is very unique.

Thanks for posting the picture Bill.

[C10 - C90 Bill]

By the way, for those not familiar with that truck, it was a '72 GMC MH 9500 (Extended Hood) with an 8V-71 Detroit.

Bill

[C10 - C90 Bill]

For comparison, the Shifting Sequence on the ones I call "more common" would be:

Aux - Main

2DO - 1

2DO - 2

2DO - 3

2DO - 4

------- 5

13 Speeds altogether (On Road)

[63 & 64 Bowties]

Originally Posted by C10 - C90 Bill

By the way, for those not familiar with that truck, it was a '72 GMC MH 9500 (Extended Hood) with an 8V-71 Detroit.

Bill

Yup, we both wanted that truck and someone else beat us to it....

[greywuuf]

see that is what I was talking about, the yellow truck seems to be a "mis match" where aux and main gears "overlap" and you end up with combinations out of sequence, I guess I would prefer to think of it as a Gear and a "range"

all though I do not see it mattering to me a whole lot as i will likely NEVER load the truck to the point I will need anything like all of the gears, buying a semi to use like a pickup.

now I take it on a quadraplex or a "real" truck transmission it would not operate like that? it would be an actual splitter ?

[greywuuf]

Oh and I take it that it is "normal" for the brown lippe and Spicers designed as aux's to have the the around the corner or horse collar pattern as compared tothe "H" pattern ?

[C10 - C90 Bill]

Dan,

That is how 5 X 4's are, I believe they all "overlap".

Even a 5-Speed Trans, 2-Speed Rear can overlap.

Check out the Shifting Sequence on my '62 6500:

1L
1H
2L
2H
3L
3H
4L
5L
4H
5H

My '67 7500 also shifted that way.

Bill

[greywuuf]

why the hell did someone not do this correctly ?

that is just plain lazy and poor engineering.

[Bob B.]

Originally Posted by C10 - C90 Bill

Dan,

That is how 5 X 4's are, I believe they all "overlap".

Even a 5-Speed Trans, 2-Speed Rear can overlap.

Check out the Shifting Sequence on my '62 6500:

1L
1H
2L
2H
3L
3H
4L
5L
4H
5H

My '67 7500 also shifted that way.

Bill

We had a '80 C-6500 that shifted the same way.

It all depends on the gear ratios of the transmission and aux. or rear axle. Not all 5 speeds are the same, some are O.D. 5th., direct 5th., short 4th. gear, ect..

[1976gmc20]

My understanding is that in most of the "brownies" the lowest gear is effectively a "low range" that you don't normally use to split main gears. So you just use the top two or three.

I drove a 5x3 (big gas six) for a while, and I think I shifted it something like this:
2-123
3-23
4-23
5-23

But keep in mind that truck drivers skip gears all the time depending on conditions, even on a 13sp RR. With not much load, you could probably just use the top two brownie gears like a 2-speed axle.

I used to work for a guy that had a KW and a Pete, each with a 13 and a 4. Imagine trying to keep track of all those 52 gears

[Ugly 61]

The 5 speed shifting pattern with the 4L-5L then 4H-5H is known as a working 4th and usually is found on 2 & 1/2 ton Chevy and GMC Medium trucks with a 5 speed Clark trans.
If the rear axle gears are right it works great, I have put thousands of miles on a C65 with this shift pattern

[junkmandan3]

"Working fourth" or short 4th five speeds are GM's answer to take advantage of the ratio split in a 2 speed axle that enables you to keep the RPM split in the top 4 gears even . In the case of my 4-53T in my pickup it works out to a 300 RPM split instead of 500, utilizing the 27% split in the auxilliary which is similar to the split of a 2 speed axle . I believe GM collaborated with Spicer to design the ratios which is about 17% in 4th gear.