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M1088 Transmission cooler fan question

rigsales

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Is this fan designed to stay on all of the time or does it operate off of the trans temperature somehow? I've searched the TMs and cannot seem to find the answer. (Of course not saying it isn't in there somewhere).
Mine is not running all the time but does come on occasionally. When I stopped to refuel the diesel tank seemed very hot to me but trans temp light never came on and water temp stayed under 200 degrees. Engine fan would come on occasionally as well since I was just taking it easy. Using a temp gun the trans pan was about 220 degrees.

I'm trying to get a M1088 home to Oklahoma from Bardstown Ky. I had to have a rear driveshaft built in Louisville because there was not one in it but I knew that going into this. It made the price right in the Auction so I went for it. The part numbers listed here helped a ton and thank you to everyone for the great threads and info. One weird thing on the shaft, the truck had the D stamp by the Vin but when I gave the shop the spicer numbers for the driveshaft parts the said it was for a 4" shaft and the one I brought to them was a 3 1/2" shaft. They also said it was a very thick wall material. When I was installing the driveshaft the rear yoke had Significant play and I assume this probably caused the driveshaft failure in the first place. I went ahead and drove it 200 miles taking back roads and cruising at about 45 mph. I didn't feel comfortable doing it and I just kept waiting for it to throw the new 1,300 driveshaft out (that was new yokes as well). Not sure which is which but part numbers are
S15-4-6281X - end yoke - paid $240
S15-46261-1 - end yoke - paid $267.
All the driveshaft numbers are on the sticky - they used 17" of S132-30-72
I Made it to Paducah Ky last night and ordered the rear end pinion bearings and seals this morning which will be here tomorrow. All part numbers in the TM came right up and we're easily ordered.
bearings are Timken, HM813844 and a 66589.
seals are A 1205 U 2257 and 1205 F 2502
I've looked at the TMs and some more helpful threads and it doesn't seem like it will be to tough of a job. Remove driveshaft, (I did also buy another new u-joint today just in case,,, their number was 2104*5279X at the local Mack shop) use a 2 3/16 socket to remove yoke nut and then pull the pinion nose out after removing the 8 bolts holding it in. I had to replace the yokes as well so it should come off easier then the broken ones did. Replace bearings, races, and seals, install the nose and driveshaft, and be on my way. I'm not sure why I get myself into these situations but I guess that's half the fun of it huh? So I will find a nice parking lot tomorrow, I have drain pans and oil diapers to make sure I don't make a mess.
Oh, I also had to replace that small o-ring on the cab release. It was puking oil out of the latch side and couldn't raise the cab it was so bad. While reading more TMs today I figured out that the lower right knob on the cab raising console that says "cab" and also (push and turn to right to lock) is to engage the cab airbags. Didn't have it in the first 200 miles, cannot wait to try it with the air ride.
other than that just typical CTIS gremlins but tires are all up. All the lights work and blinkers. Steering tilt lock know was gone so I had to rig up a bolt nut washer washer washer setup that holds ok for now.
Again, the threads on this was a great help. I know this is a long post just to ask that one question but wanted to share just in case it can help some buddy else someday. Thanks! I will let you know how it goes and take some pictures as well.
 

coachgeo

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I... I had to have a rear driveshaft built in Louisville because there was not one in it but I knew that going into this. ...
Keep eyes open for other potential issues. It has been said that what is left removed or disconnected... while it may be it was robbed to repair an another rig it may also be just where they stopped after recognizing other issues in that area thus decided to let this one go. So you might consider the missing driveshaft a hint about something else wrong in that line of things. Example..... check the rear axle for metal in fluid, check play at the Axle ujoint etc. etc.

PS... If you cross over the Paducah ****...... Say hi for me to great engineer. My Grandfather built that dam as the On Site Construction Engineer.
 

rigsales

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Thanks for that, I sure will honk the horn for ya,

that is why I'm so gun shy on this one. It actually broke on the Auction guy while he was moving it. He did include the broken one for me to show the driveline shop. Truck has 18K miles and rear end yoke is sloppy with play. I hope this caused the u-joint to eventually fail and threw the shaft. Going to look at the rear end gears closely when I get that pinion nose off. I already replaced the rear end fluid and no big metal pieces so hopeing for the best.
 

coachgeo

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Thanks for that, I sure will honk the horn for ya,

that is why I'm so gun shy on this one. It actually broke on the Auction guy while he was moving it. He did include the broken one for me to show the driveline shop. Truck has 18K miles and rear end yoke is sloppy with play. I hope this caused the u-joint to eventually fail and threw the shaft. Going to look at the rear end gears closely when I get that pinion nose off. I already replaced the rear end fluid and no big metal pieces so hopeing for the best.
Do not drive it if play in rear end is out of spec. The TCase housing mounted to the rear of these tranny's do not handle slop/vibration like an old truck will. You'll chance grenading your Tranny. Don't ask me how I know. Seems to have happened to about half dozen other folk as well. your looking at $$$pendy if that happens. Like..... possibly as much as you paid for the whole truck.
 

rigsales

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Good deal, thanks.
made it home finally, when I would stop and check temps with a temp gun the transmission was about 220 degrees and I never saw the trans fan on when I would stop. I really don't think it's coming on at all so I might hook it up to a switch and install a temp gauge so I can monitor and control from the cab.
You can sure tell when the engine fan cycles though, it's like throwing a parachute out the back and load as heck. I might look into some auxiliary electric fans I've read some people doing. When I turned the heat on yesterday morning it would rarely cycle the engine fan.
The rear end bearings were fine, the mechanic who was "helping me" just didn't torque the yoke nut enough to set the proper preload on the bearing. Was kind of glad I didn't have to get those bearings off the pinion shaft in a parking lot.
 

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scottmandu

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Pinion bearing preload is determined by shims on the pinion. That looks like am improperly set pinion depth.
 

rigsales

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Thank you for that,
it was the bearing on the other side of the pinion nose (under yoke) that was loose. From the TM breakdown it looks like the nut and yoke tighten onto that outer bearing setting the load on that bearing. I used a 1" drive impact and tightened until the bearing felt tight but still turned freely. I will look for the proper procedure in the TM's. the backlash felt good and it went in smoothly but I should still fix it to spec for sure.
 
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