we have an 85 L8000 flatbed with a Cat diesel, 5 speed spicer trans and 2 speed rear end

On the highway in 5 gear and the rear in high, the motor is screaming going 55, while state dump trucks loaded blow past me lol
Did they have overdrive trannys in these trucks in 85?
Whats the best way to make this into a highway cruiser?
this damn thing is geared so low i start in 2nd and keep the rear in high all the time

 

Dunno how deep your wallet is, but a 2:1 (or 1:2) under/over-drive unit might be the easiest. The other option, of course, is regear the rear, or get an overdrive tranny.

The rest of the "big" people here are sure to come along soon...

 

Cost-wise, the rear gears are the better option. Next in line would be a trans swap to one with an OD. I wouldnt recommend cranking up the governed speed just to go faster.

 

Find your model number for the rear axle and determine the ratios.

You may be able to find them on top of the diff per this:

http://www2.dana.com/pdf/AXSM-0040.pdf

(page 4)

You may be able to find a 2 speed with taller ratios. Not sure how to research and find those but there's tons of hits when you search "Eaton ---"

 

I had the same problem with a 5 spd direct and 6.43 gears in the rear I topped out around 50. I swapped out the rear for a single speed 4.56 chuck and put in a 6 spd direct. Then after watching some youtube vids from nvrenufhp, did some pump tuning and it seems to be a good combination all around. I would swing the rear end gears if I were you.

 

You can find a link to nvrenufhp's "turn ups" for diesels in the Tech Folder in this forum.

 

I checked the tag on the tranny and its a spicer CM-6052-A which is 1:1 in 5th.
What are my options for swapping to an overdrive trans, like bellhousing, linkage, output shaft?

Also i see some trucks have auxiliary transmissions, is that like an overdrive unit or something?

The axle seems to be an Eaton 22A according to the tag on the housing, i cant find the gear ratio anywhere on the carrier but the axle code on the door sticker says "JBL"
Ive searched and cant find a list of axle codes for these trucks anywhere
Anybody know where to find them?

Are there any junkyards in NH with heavy truck stuff?
Thanks!
Heres a pic

 

Being from NH, I've looked too for "Ford Heavy Truck Grave Yards" and havent been able to find any. I know of a couple of places that have a few Fords in their inventory, but they also happen to knwo that the parts are getting harder to find, therefore increasing the $$ of parts. P+S truck in Lunenburg, MA had a few this summer, couple of newer (90's+) L's and an Aeromax with an L10 Cummins. I have been watchin craigslist and occasionally heavy stuff will come on, someone parting one out.

And as for puttin an aux in, well, that would be a lot of work, fab work to hold it up and such. If I was GIVEN one, i might consider this.

Pretty much all you need to know for a tranny swap is weather it is a SAE 1 or 2 bell on the 3208 and what size your input shaft is. I would say an SAE 2 with a 1 3/4 input shaft, and different pilot bearings can be bought at Sanels. An overdrive would allow you to go faster, but. . .

The cheapest and easiest way out would be a rear end center section with a different ratio, for probably 1500ish Cash+Carry at Camarota.

When I did mine, I considered doing an overdrive tranny, but when i would coast down a hill to get 55 out of the old setup, I would get a serious driveline shake and vibration, from the driveline coming out of harmonics. That was when I made my decision to lower the driveline speed and swing the chuck out, and have had good luck.

 

look at this page (bottom link for Yours) Eaton info:
LiteratureCenterResults

Page 3 will tell you about the numbers stamped into your axle that are needed to id your unit (they are on the top center of the pumpkin.)