Geoff Weeks

Oh, I used mine a lot, descending grades, slowing to exit, etc. Years ago, I was in Boomtown, at night when I heard a 6-71 with jakes descending from Truckee. An ancient Freightliner cabover (round headlight) pull in next to me. His was also muffled, but no mistaking a 6-71 with a jake. Not something heard anymore.

Oh boy, one of "those boys". All my semi's had Jakes, either came with them or I added them, BUT all had mufflers. They were for holding the truck back at speed when descending, often with permit loads, not to make noise. Never had a problem even in "no Jake brake towns". Changing engine to be able to make noise, seams like buying a house so you can burn it to have a cook out!

I'll freely admit I like old stuff old. My advice to you is since this is your first "at bat" with a semi sized/type vehicle that if the original engine can be made runable, then go with that, at least at 1st. There are many reasons, but top of the list is it fits and doesn't require any changes. 2nd it lets you get a feel for the truck. No point wrestling a 3406 into the truck to find you can't cool it. I modified every semi I ever owned, but only after putting some seat time in to find what works and what could be improved. You can always come back later and make changes. I know of more than one vehicle that has never been finished because the owner keeps making changes to his original project, some because the original plan was not practical others because he wanted to make it "better" without ever finding out if it was good enough already. My take on Super Singles is: they can cut a very little rolling resistance on a loaded truck that puts 100,000 miles or more a year on, but have serious drawbacks that I found outweighed the benefits many time over. duels allow the same rim/tire front to back. Duels allow you to "limp"off the road when one fails tires are much cheaper rims are much cheaper duels are much easier to handle, change and lift/postion. If loaded when you have a blow-out on a Super Single it most times take the rim with it before you can get stopped. Now your looking at a $1500 or more tire change before including the road service call. SS are too big, heavy and expensive to carry as a spare. Given all the above, I ran duels, but more than that, they look right on an old truck, SS are a new thing.

Trans and rear need to be considered together. Total overall ratio is what is important. If it is a hobby truck, then start ability under load is not a big deal. It looks to have some form of front loader rear gear, so not likely hard to find other ratios. 4.10 with a .73 on 20" rubber will top out at 80 easy. 3.91 a bit faster. 3.70 or there abouts with a .83 OD will do the same If the trans is direct in top you want 3.54 or less for the rear. going to 11 x24.5 shift the numbers a little but not much Trucks, and old trucks in general should have duels not SS in my opinion, but that is just an opinion.

I had a small cam SAE #1 that had 3/8" bolt holes, but I doubt it was as old as 1953? Came off a CPL 150 small cam engine.

from the ad 'CLUTCH HOUSING FORCED LUBE ALUM' which I believe would make it for a late model RTLO series? As far as cross shaft, they are OEM not an Eaton part, as each mfg had their own linkage . I would think your original and fork should fit if reuseable. That is the idea behind the SAE spec. To bad Glenn is no longer with us to answer these questions. The following are just guesses subject to correction: The RTLO used taper roller bearings on the counter shaft, the earlier ones used plain rollers, I think the taper rollers had lube fed to them from the pump, early ones could have a pump or not, mainly for an oil cooler circuit. I think the SAE spec sets up the distances and the different clutch assmeblies conform to those distances? In otherword a window is in the spec and how the clutch designer meets that window is up to them? It would seam the pull design allows for more compact design and allows the yoke to be placed slight closer to the flywheel, where as the push has to ride on the front bearing retainer so has to be (slightly) closer to the transmission. Likely why we see more pull clutches in multiple disks and push in more single disk clutches? I thought the reason you were looking to stay with push is so you can use what you have now? Double disk pull will make finding clutch parts easier as they have almost taken over. If it were I (I like spending your time and money!) I would buy the used iron nodal with the lower holes missing and bore the boss from the dimensions from the Eaton .pdf, and fit your cross shaft and yoke. you have all the info to locate the holes, getting them true is the issue and that comes down to the machinist's skill and what tool they have. Not me! but you seam to have access to what is needed. It seams Mack used the nodal mount so mounts and isolators should be "off the shelf" items and you may have scrounge the frame brackets and re drill the frame, but will end up with something that is more or less stock. If at a later date you decide you need a multi disk pull the same clutch housing could take a top shaft and yoke. Aluminum makes machining easy, but may not be as strong in a nodal mount as iron. May be why they are harder to find? Just spit-balling, it seams you have to machine a clutch housing and keep the same clutch, or replace the flywheel with one for that engine that is made to accept a pull clutch and install a new linkage. Both are do able (assuming part can be had) and both are viable for long term use. I don't think one is better than the other, but I never wore a clutch out even heavy hauling, I used 14" double disk organic. For hauling your race trailer I don't see you wearing out a clutch either!

Just a thought from someone who has gone through the re-ratio deal. Look at what you can find, then do the math in each gear for startability, ratio jump (progressibilty) and top speed, and decide if it does what you want. The wrong match, free and delivered to you is more expensive than the correct match you have to search out and pay a premium for.

As far as top housings, you can swap them as needed. The question I have is what O/D ratio are you looking for? The "std" is direct in 12th and OD of .86 (?) in 13th. The old "double OD or RTOO is something like .73 in 12th and .68 in 13th but rare to find but can be "built". New RTLO boxes have a different gear set that is direct in 11th a .83 in 12th and .73 in 13th or something like that. I'd have to go into books to find the exact ratios. If you are buying from a yard, they should be able to set you up with the shifter position of your choice. If you are buying from a private sale you may need to take it as it comes, and buy a cover to get the position you want. Std cover for a double OD has top gear against the dash, but an X bar cover will give you conventional H pattern. They came about when more "steering wheel holders" than drivers entered the market and couldn't deal with the last two gear positions being "reversed" from what they were used to. Older = cheaper, but even the RTLO series is now "older"

In that case, the A-6064 is what you want. You are likely to need a hanger at the back end of the transmission if you get away from the nodal mount for the rear engine mount. I learned quite a lot doing the research on your issue. I had always thought that the bells with the lower holes were for push clutches, and now know that they can be or can be for lower pull clutches depending on placement of of holes. I hope you now have enough info to carry your project to fruition.

This one has the correct drilling of the lower shaft for a push type clutch, but unfortunately is not nodal mount. https://www.ebay.com/itm/296632014527 If you look carefully at the pictures you can see the lower shaft is toward the transmission side of the housing more than the upper. Flipping between the last two I posted, I think one could locate and machine the nodal mount one to take a push clutch shaft. That is as close as I have come.

This one is nodal, but the bottom bosses are not machined out. The above post with the .pdf has the drawing with the dimensions to locate the lower shaft for push applications. https://www.vanderhaags.com/detailview.php?manufacturer=fuller&model=a-4456&inventorytype=transmission-clutch-housing&wcf=model If you have the ability to do the machine work or know someone who does, you could make a push bell with nodal mount with the info we now have. It would appear that Mack uses the symmetrical nodal mount from what I can glean from the E bay listing.

This says it is for Mack, seams to be double bushed for both over/under but listed pull only https://www.ebay.com/itm/292528684947

Top cover should be any problem RTO is std cover RTOF is foward set shifter cover. I assume you're looking to make a RTOOFxx5 or6 13? I am getting no hits on any of the numbers other than the 6064, and that is suspect for being a Nodal mount. From what I have read, you don't want anything new than a "6" trans and they are now so out of date that they aren't what show up most of the time. 5 series is "course gearing" 6 series is "fine gearing" 7 is the start of the low inertia series transmissions. I take it you are looking for a .68 top O/D gear?

Hum, 6064 is listed as both nodal and non nodal and any pictures I see are non nodal? So not sure we are out of the woods yet.

Wooo hooo! I found what you need to know! https://www.redramgear.ca/wp-content/uploads/2015/05/eaton-fuller-transmission-identification-guide.pdf A 6064 is a nodal with symentrical mount bolts in aluminum with both push and pull A 4373 is a nodal iron for push clutch only A 4232 is a iron nodal in SAE #2 Hope this helps

Found this: https://www.eaton.com/content/dam/eaton/products/transmissions/vehicle-transmissions/eaton-transmission-clutch-housing-selector-cmt1540-en-us.pdf It seams to imply that push and lower pull are NOT the same on the cross shaft (learned something new) and I can't find a push nodal mount for the older transmissions. SO I may be wrong. That said if you can fit a double disk pull flywheel, the trans with the nodal mount shouldn't be hard to come by.

I THINK this is what you are looking for: Nodal mount Push and pull Clutch Doesn't say what model trans it came off https://www.heavytruckparts.net/item/Mack/-/Bell-Housing/297005/1/83669829 What I remember, but DO NOT go off my memory alone, that the newer model Roadranger trans bells are different than then earlier (pre RLO) -6 and older transmission clutch housings, although they look similar. edit: it doesn't look like the lower bosses are machined out for a push clutch, the bosses are in the casting but they haven't been machined.

This is what you need I think: https://www.vanderhaags.com/detailview.php?part=25092981 Wait, that one doesn't seam to have the lower cross shaft holes, They have a few that are both but most are pull only. What is confusing is the replacement are all set up for either, but I guess the OEM are one or the other.

Is yours #2 or #1? Measure 1st, there are plenty of drawings on the internet that show the measurements for the SAE bells. Eaton uses the same trans bell for push and pull, there are two sets of holes for the cross shaft an bushings. Top set are for pull, bottom for push. edit: this seams only to be true of "replacement" housings, original can be one or the other or both. Bells are the same for all the older -6 and down roadrangers, the lighter rated ones tended to be aluminum, the heavier rated ones tended to iron. So, in other word a RT11609 would likely be found with an aluminum bell but a RT14609 would be more likely to have an iron bell, but you could interchange them. I have an aluminum R/R bell but doesn't have the nodal mount you need, otherwise it would be yours. The trans can be switch from push to pull or visa versa by changing the input shaft and front bearing retainer.

I know the 1st gen Volvo/White conventionals used nodal mount with pads for engine mounts on the trans half of the bell housing. A 4 bolt pad on each side not exactly vertical to which mounts were bolted.

You can put washers on the 3/8" bolts when putting them through a trans side bell with 7/16" hole. The bolts don't center the bell, the ring on the inside does, so the "slop" makes no difference in alignment.

Old #1 used 3/8" bolts (something Iearned about the hard way) at some point they switched to 7/16 threaded holes but all other dimensions remain the same.

I'd start by looking up what the SAE housings and flywheel standard covers. You might be pleasantly surprised. The whole idea was if it was standardized, then anything that fit a #1 housing had to have the same mounting depth etc. The only push clutch I have dealt with was SAE #2. I'm assuming yours is #1. Getting the right Eaton half of the Bell with the nodal mount may be the hardest thing to find, as input shafts and bearing retainers are often changed as a matter of course when a clutch job is done. A internet search had a few hits from the common suppliers. I never saw the point in replacing parts that weren't worn beyond service ability, but my clutches often lasted until the engine had to come out for some other reason.

FYI, I get a few hits for the push clutch bearing retainer (around $200) but almost nothing for the 2" push clutch shaft. If your serious, I would start looking for the shaft before going further down this road. S-1129 or S 1129a Did a little more searching and found alternate FBC and input shaft. Don't know the difference but both seam more available S 1660 & 20549 for part numbers I think I found the difference between the 1st set of numbers and the 2nd set. The 1st set uses a rubber seal on the input shaft and can be driven in either direction. The 2nd set uses a "screw seal" like the pull clutches and can only be turned in the conventional direction

I thought, but never verified, that the SAE spec meant that the input shaft length and depth to crankshaft was part of the spec regardless of what flywheel and clutch was used. The input shaft for push clutches are different than the one for pull clutches, I know. I don't think the length changes though. After all the pilot bearing sits against the crank, and the spline on the shaft runs up to the pilot. The difference is at the bearing retainer end, the shaft has to run through the tube on the retainer that carries the throw-out bearing. Eaton's can be had with nodel mounts on the trans 1/2 of the bell, Volvo also used that arrangement. Having said all that, I have never seen a Eaton with a push clutch. However, you are going to need the push clutch shaft and bearing retainer regardless, if you have the trans already, then I would buy the shaft and bearing retainer and measure and compare to the trans you have now. You still need a Nodal mount trans half of the bell, but they should be out there, I know the Volvo/White/GMC (early 80's) used that as one place I worked had 2 of them, and I put clutches in them, and remember it was a pain having to support the rear of the engine while I did so. I think it would make life simpler not having to re design the whole clutch and linkage.