Has anyone added an OD aux trans to their truck?

[5Tractorguy]

Was thinking of doing this in my '77 K25 so I'd have a "highway gear", or at least drop my RPM from 2800 to around 2000 at 65mph. It would have to go behind the t-case and could only be used in 2WD, which isn't a problem for me. Preferably a 2-speed box, direct and OD. Would rather not go with the Gear Vendors overdrive unit since I don't have an extra 3-4 grand to play with.

Anybody successfully done this with pictures? Or, any recommendations on a truck salvage yard/company that may have used auxiliary transmissions?

Any direction/thoughts are appreciated.

[nonstop]

I have done it, and frankly, I’m probably taking it out. I have the venerable Spicer 5831b backed with 4.56 gears. It is a neat little novelty, but that’s about the extent of it. I don’t use my truck enough to justify it on the freeway, and it’s loud in overdrive. On top of it, I’m not sure how much parasitic loss I have from running an auxiliary, but my mileage isn’t really any better.

Now, I WILL say that I just converted back to rear drum brakes from disc, and in doing so, discovered one of my rear calipers was dragging to the point I had to pry it off. That said, I’m guessing my mileage might increase, but I’m still probably going to get rid of the Spicer and change gears to 3.73’s.

Oh and I got mine for a deal, but by the time I chased down a shifter, put in new seals and bearings (still leaks quite a bit), and chased down the driveline parts and parking brake set up (rear discs, so I didn’t have one with them), and the time, I was into it close to $1000 or so.

[5Tractorguy]

Originally Posted by nonstop

I have done it, and frankly, I’m probably taking it out. I have the venerable Spicer 5831b backed with 4.56 gears. It is a neat little novelty, but that’s about the extent of it. I don’t use my truck enough to justify it on the freeway, and it’s loud in overdrive. On top of it, I’m not sure how much parasitic loss I have from running an auxiliary, but my mileage isn’t really any better.

Now, I WILL say that I just converted back to rear drum brakes from disc, and in doing so, discovered one of my rear calipers was dragging to the point I had to pry it off. That said, I’m guessing my mileage might increase, but I’m still probably going to get rid of the Spicer and change gears to 3.73’s.

Oh and I got mine for a deal, but by the time I chased down a shifter, put in new seals and bearings (still leaks quite a bit), and chased down the driveline parts and parking brake set up (rear discs, so I didn’t have one with them), and the time, I was into it close to $1000 or so.

I didn't even think about the OD whine. My '61 GMC 5000 has the older style 5531 Spicer that I installed to get me over 35mph. When you shift into overdrive and get it up to speed, you have to talk loudly to whoever is in the cab, can't listen to a radio etc... Rather not have to deal with that in the '77.

So by the time I'm done installing it, I could have spent that money on gas really, pretty much cancels out unless I was driving it a ton. I bought my 5531 for $500 I think? And had it shipped in from SD... I doubt I'll find a deal like that again.

Well, I suppose I'll just drive it (every once and a while I get a hair-brained idea!) This truck used to go back and forth between CO and NH up 'till 3-4yrs ago. I'm sure a trip to PA next spring will be no issue. It's done plenty of 100mi/+ trips around NE this year.

[SunSoaked]

I contemplate it from time to time. Then I come to my senses and remind myself that I can get a good used LS/4l80 setup for less money. And that's the end of that.

[MalibuSSwagon]

What transmission do you have?

This is a thing for Sm465/Sm420 trucks.

https://www.advanceadapters.com/prod...etainer-index/

[5Tractorguy]

Originally Posted by MalibuSSwagon

What transmission do you have?

This is a thing for Sm465/Sm420 trucks.

https://www.advanceadapters.com/prod...etainer-index/

SM465.

Oooh, I like that! Saw one similar searching the web last night. Someone installed one in a 60's or 70's truck resto they were doing. Still out of my budget though...

[sweetk30]

nv4500 for the stupid simple win .

[44th Miss Inf]

Dad put a little 3 speed Spice (may have been an older Brown-Lipe) in a 64 Chevy 3/4t behind a 6.2 diesel and a 465 trans.

It's tucked in the back of my barn since he passed, but will try to remember and get a few pictures Friday or Saturday when I'm off work

[DieselSJ]

Originally Posted by 5Tractorguy

SM465.

Originally Posted by sweetk30

nv4500 for the stupid simple win .

/Thread