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Transmission Seal Leak
Took my bus for a pleasure cruise yesterday. When I got home, I noticed some wet spots on the back of the bus. So I looked underneath, and could see that the Allison B500 transmission output shaft seal is starting to leak. I’m a DIYer.
Does anybody have the part#?
Has anybody changed it themselves?
Thanks
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9 Replies
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Not just the seal, most likely the drive shaft yoke will have a groove in it and will need to be replaced, also the nut on out put shaft has a hellacious tight torque spec. Prevost will have the parts and were competive with allison on price, also had rebuilt yokes. good luck
Glenn
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Bought the seal today at Stewart Stevenson for $71. It’s a National/Allison pt# 29552705. Thing is HUGE! It’s bigger than my flip phone.
This seal leaking is a common problem with old Allisons that were manufactured before synthetic ATFs came to market. I run Allison approved High Capacity filters and Mobil Delvac 1 synthetic TES-295 ATF. The old original seal is not totally compatible with TES-295 synthetic ATFs, this according to ex Allison Fluid Engineer Tom Johnson, now with JG Lubricant Services JG Lube
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I have a slight weep on the output seal too. Please keep us posted on repair progress/procedure. Does not look like a walk in the park.
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I changed my Allison B500 output shaft seal today. Easy job. Six bolts. The yoke was fine. It slides off the shaft with 1 hammer tap after the 2 small 15 mm bolts are removed. The 4 bolts that hold the u-joint straps are 1/2″ 12 point.
Lubed everything on the rear of the bus while I was at it.
Old bad seal # 29515691. New seal # 29552705.
I plan to change the fluid and filters again soon. I don’t know what was in it when I bought it. I changed it 4.5 yrs and 18k miles ago with Mobil Delvac 1 synthetic, an Allison approved TES-295 fluid, and Allison high capacity filters. I’ll take a sample an send it in for analysis and see if it needs changing first.
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Thanks for the pictures, Don. That looks actually quite doable. Did you have to drain the transmission fluid? I’d guess not because the sump is so much lower.
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Excellent post. Free dues for a year!
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There is zero fluid loss when the seal is removed.
Thanks
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Way to go Don! you da man, I’m also a DIYer and next oil change i will change seal, did you replace those 2 little seals?
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No, u dah man
I had no idea they were there. if I ever see those 2 bolts heads wet, I’ll know the fix.
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