BAD DOG Posted July 6, 2016 Share Posted July 6, 2016 Looking for you guys opinion on this. My Superliner is a glider originally it had an 866 V-8 with a 12-spd and 4:17 rears on 11R24.5 rubber. When I rebuilt it after the accident, I put my E9 in it with a 15-spd Fuller and newer Eaton rears on hub piloted wheels 3:90 on 11R 22.5 rubber. Used to run 68 MPH at 2100rpm before. Now with this drive line, I do 68 MPH at 1700 rpm. I'm thinking this 15-spd is an overdrive. I know the 12-spd was a direct. The 15-spd is giving me grief. I think it might have got done in when it was towed with the driveshaft still hooked up? It's extremely sluggish going from lo to hi range and worse from hi to lo and has something not right with 4th gear. It doesn't slide in like it should I have a line on a couple of newer 12-spd overs. I'm thinking of switching. What do you guys think before I go trying one and cutting down a perfectly fine driveshaft? If not I was thinking of a 13-spd Fuller since I have the bell housing for the Fuller already. I'm kinda looking for something with a shorter space between top gears and I know the 12-spd will be similar to the 15-spd. Plus it's only a hobby truck so I'm not going to spend a fortune. I doubt the 15-spd I have would be a cheap fix. What do you guys think? Quote Link to comment Share on other sites More sharing options...
alex g Posted July 6, 2016 Share Posted July 6, 2016 I'm a 12 speed fan I actually learned to drive on one. I'd go with one if I had to change it anyway. Sent from my SM-G386W using Tapatalk 1 Quote Link to comment Share on other sites More sharing options...
bbigrig Posted July 6, 2016 Share Posted July 6, 2016 (edited) I would stick with the Fuller and go 13spd. Easier to change over and easier on the pocket book down the road. As neat and nostalgic as the TRTXL1070B (12 speed air shift deep reduction with OD) is, its a lot more work and money if something goes wrong down the road. That and a lot of work to put in. (mounts. Piping, driveshaft. etc) 13 Fullers are everywhere. It's up to you.... Fashion or Function, pick your poison. Edited July 6, 2016 by bbigrig 1 Quote Link to comment Share on other sites More sharing options...
Truck Shop Posted July 6, 2016 Share Posted July 6, 2016 What series of 15 speed is it, RT or RTO? The fifteens really are no more expensive to repair than a 13. The rear sections are pretty straight forward when it comes to rebuilding that area. The front is no different than any other Eaton front section when comes to repair. When you say sluggish from Lo to Hi does it grind or just slow to change range? If it is just slow remove the supply hose from the regulator to slave valve on the left side of trans and squirt some air tool oil down that hose and reconnect. Then operate the range selector usually it will speed up the shift. The slave and range cylinders can get dry and cause that condition. Next I would remove the shift tower and manually shift to fourth to check for stiffness, But check the shift tower and shift lever too. Truck Shop Quote One ping only Link to comment Share on other sites More sharing options...
BAD DOG Posted July 6, 2016 Author Share Posted July 6, 2016 4 hours ago, Truck Shop said: What series of 15 speed is it, RT or RTO? The fifteens really are no more expensive to repair than a 13. The rear sections are pretty straight forward when it comes to rebuilding that area. The front is no different than any other Eaton front section when comes to repair. When you say sluggish from Lo to Hi does it grind or just slow to change range? If it is just slow remove the supply hose from the regulator to slave valve on the left side of trans and squirt some air tool oil down that hose and reconnect. Then operate the range selector usually it will speed up the shift. The slave and range cylinders can get dry and cause that condition. Next I would remove the shift tower and manually shift to fourth to check for stiffness, But check the shift tower and shift lever too. Truck Shop It's slow to go from lo to hi when going up through the gears you have to let the rpm s drop right down to 1100 for it to go into 6th. Then when you go back from hi to lo you need to almost come to a stop sometimes. I tried the air tool oil in the spring. You need to move the button from lo to hi and back before you move. Maybe it needs a kit put in the slave cylinder. Quote Link to comment Share on other sites More sharing options...
Truck Shop Posted July 7, 2016 Share Posted July 7, 2016 Check the air pressure on the delivery port of the regulator. Should be 65 psi, if not then you have a regulator problem and those are not adjustable. It's an air shift problem, I doubt there is anything wrong with the back section. You want to put oil in it after the regulator not before or in the supply hose. Truck Shop Quote One ping only Link to comment Share on other sites More sharing options...
BAD DOG Posted July 7, 2016 Author Share Posted July 7, 2016 Thanks Truckshop. I went out to the shop and took the line off after the regulator again like I did in the spring and put more air tool oil in it. It seems to be quicker now I might take it out tomorrow if I get done work early. I don't doubt it could be a regulator issue also. When I was putting the truck together I had an issue with some off shore Taiwan go imitation Fuller parts from my one parts supplier. I had the shifter knob itself being no good from the get go so I ended up paying a bit more getting a real Fuller one at Mack dealer. The regulator was also a cheap imatation so it could vey we'll be my issue. For the sake of 2 airlines and 2 bolts and a few minutes to do it I think I'm going to try and get a real Fuller one for what it's worth. The tranny is a RTX 15715 . Quote Link to comment Share on other sites More sharing options...
Truck Shop Posted July 7, 2016 Share Posted July 7, 2016 The X in the RTX stands for overdrive and that is a good gearbox. I've rebuilt a lot of Eaton/Fuller transmissions and I only use Eaton parts. Mack gets Mack parts, Cat gets Cat parts. Lol Truck Shop 1 Quote One ping only Link to comment Share on other sites More sharing options...
BAD DOG Posted July 13, 2016 Author Share Posted July 13, 2016 Put a bunch more air tool oil through it. Seems much better, got another regulator I'm gonna put on and make sure it's getting 65 psi through it. . I took it out tonight up and down the road a few times, it was better at first but got lazy again , gonna keep playing around with it, it's not a daily driver so I'm gonna play with it more and try and get things freed up. What weight of gear oil should you be running in it? I have 80w90 in it right now with a couple quarts of Lucas with it. Just wondering if it should have something different in it . The slave cylinder gets lazy after it moves and you need to play with it putting it in different gears to get it to go from low to high and back quick and smooth again. Quote Link to comment Share on other sites More sharing options...
Truck Shop Posted July 13, 2016 Share Posted July 13, 2016 You should either use straight 50wt motor oil or 50wt synthetic transmission lube. But in your case 50wt motor oil will be just fine. Truck Shop Quote One ping only Link to comment Share on other sites More sharing options...
BAD DOG Posted July 13, 2016 Author Share Posted July 13, 2016 2 hours ago, Truck Shop said: You should either use straight 50wt motor oil or 50wt synthetic transmission lube. But in your case 50wt motor oil will be just fine. Truck Shop Ok. Thanks, I was wondering if 80w90 was too heavy for it. I'll give the 50 wt a try. Thanks. Quote Link to comment Share on other sites More sharing options...
Hobert62 Posted July 14, 2016 Share Posted July 14, 2016 My dad tried to add Lucas in his 5 speed chevy pickup transmission when he changed it and it was to thick. It was real stiff to shift especially on cold mornings. Quote Link to comment Share on other sites More sharing options...
Freightrain Posted July 14, 2016 Share Posted July 14, 2016 (edited) Most of the late model 5spds need ATF. They run on needle bearing gears and tapered end bearings and the clearances are tight. Anything to thicken it is no good. Unless it is really, really wore out. 15 yrs back I put 1/2 Lucas and 1/2 75w/90 in my triplex. It quieted it down a touch but made it stiff to shift even when warm. I changed it some years back to just gear lube and it shifts easier, though not as easy as I would like. Since I tightened up the rear bearing shim it got a bit quieter even with the lighter lube. Edited July 14, 2016 by Freightrain Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment Share on other sites More sharing options...
BAD DOG Posted July 19, 2016 Author Share Posted July 19, 2016 Changed regulator put some more air tool oil in the supply line coming out of regulator, and drained 80w90 gear oil out of tranny , re filled with 50 wt synthetic tranny oil . Seems much better only took it to a short trip to the corner and back because I don't have a plate on it at the moment hoping when I take it to the show up a St Thomas next month. It will free things up . Quote Link to comment Share on other sites More sharing options...
BillyT Posted July 19, 2016 Share Posted July 19, 2016 Freight train, I have an Izuzu pu daily driver with a5sp.od I put 1qt Lucas engine additive and 1 qt rotella t 15w40in it.Smoothest shifting p.u. tranny I've ever driven.Thing calls for 5w30. I think it may be the Lucas that did it! The Lucas came with the tk,so I figured I'd use it! Quote Link to comment Share on other sites More sharing options...
BAD DOG Posted August 3, 2016 Author Share Posted August 3, 2016 Changed to 50wt synthetic oil , put new slave valve and plunger pin in last week took it up the road and back a couple times is working like it should now . 4th gear is a bit touchy still but I'm going to wait till cooler weather to pull the tower off and play with that part. Quote Link to comment Share on other sites More sharing options...
Truck Shop Posted August 3, 2016 Share Posted August 3, 2016 Great ! glad it's working better. Truck Shop Quote One ping only Link to comment Share on other sites More sharing options...
Outbehindthebarn Posted August 6, 2016 Share Posted August 6, 2016 I thought all 12 speeds were overdrives? Quote Fun is what they fine you for!My name is Bob Buckman sir,. . . and I hate truckers. Link to comment Share on other sites More sharing options...
terry Posted August 6, 2016 Share Posted August 6, 2016 5 hours ago, Outbehindthebarn said: I thought all 12 speeds were overdrives? Some early ones were direct. 1 Quote Link to comment Share on other sites More sharing options...
BAD DOG Posted August 7, 2016 Author Share Posted August 7, 2016 I had an earlier one that was direct . Quote Link to comment Share on other sites More sharing options...
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