Seal leak on rear end drive unit

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flyin900
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Seal leak on rear end drive unit

#1

Post by flyin900 »

I have a small slow oil leak from the rear end of my CB1000C out of the 1/2" slot in the very bottom of the rear drive unit. I believe this maybe a drain hole for the unit if there is a seal leaking the internal Hypoid gear oil. Since the rear end is identical to our Goldwing units I am looking for someone who has addressed the same issue on a Goldwing drive.

There are a variety of seals (3pcs) inside the unit from the parts fiche and also some specific procedures if the unit is fully taken apart to reset the lash correctly. I am hoping that the offending seal can be replaced without having to get into resetting the drive gear lash. Has anyone replaced a specific internal seal to address this type of leak and if so which seal was replaced?

This leak is allowing the oil to drip directly onto the rear tire sidewall while the bike sits and maybe causing damage to the rubber. I am replacing both tires over the winter, so new tires with no leak would be great.
Current Bikes:

1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
1967 CL175K0 - Low production number with #802 engine serial- winter 2019/2020 full restoration.
1972 CB350F - Baby Four with low mileage - Cosmetic refresh to the next level 2021/2022.
1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
1984 CX650E - Restored summer 2017 - a rare Eurosport model - excellent one owner bike.
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gregforesi
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Re: Seal leak on rear end drive unit

#2

Post by gregforesi »

I rebuilt a GL1000 unit. Yours is a GL1100 unit.
The gear lash is related to the gears themselves. Assuming that the unit was originally built correctly and shimmed correctly, then putting the same gears back in with the same shims will give the same gear lash. (The shims are called "spacers" in your micro-fiche.)
The only fussy part of a full rebuild (I had found a 3.70 GEM gearset to install) was the pre-load adjustment of the pinion gear bearings. Replacing seals around the ring gear will not affect that.

It looks like you'll need to make a tool to remove and re-install the ring gizmo (part 11) that holds the outer seal. I think it has a torque value to hit...guessing worked for me.

The size of the seals is listed next to the part number. You may be able to cross reference from those numbers. The big seal is likely the problem and it is 70mm ID x 94mm OD x 6mm thick. If you only replace that seal, the job isn't very difficult, and pre-load and lash don't come into play.
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flyin900
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Re: Seal leak on rear end drive unit

#3

Post by flyin900 »

Thanks Greg,

I see that a special Honda tool is necessary to remove the geared outer ring to access the inner section with the seal. I am going to remove the metal outer cover to expose the main bolts that hold the two halves together. There maybe a leak there between the two cases that I can seal from the outside.
What tool did you use to get that geared outer ring apart, as that has splines on the outer section of the tool to engage the splines on the ring section?

Plan B..... I looked up the part number on the rear end and any Goldwing model from 1982 or 1983 uses the same rear end. So a used Wing rear end should be reasonable to purchase as a replacement too.
Current Bikes:

1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
1967 CL175K0 - Low production number with #802 engine serial- winter 2019/2020 full restoration.
1972 CB350F - Baby Four with low mileage - Cosmetic refresh to the next level 2021/2022.
1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
1984 CX650E - Restored summer 2017 - a rare Eurosport model - excellent one owner bike.
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Track T 2411
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Re: Seal leak on rear end drive unit

#4

Post by Track T 2411 »

flyin900 wrote: Plan B..... I looked up the part number on the rear end and any Goldwing model from 1982 or 1983 uses the same rear end. So a used Wing rear end should be reasonable to purchase as a replacement too.
If you buy a used unit online, be sure to get some good pics of the drive splines. It may just be my luck, but three of the 1100's I've worked on had well worn splines @ about 50k miles. Just saying...
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Current Rides:
'Grumpy' - '81 Standard, now fully dressed.
'Layla' - '81 Standard w/dealer installed fairing and Hondaline bags.
'Scarlett' '76 'Survivor' nekkid as a j-bird!

Under Construction:
The 'Jalopy' '78-'79 Mash-up
'Quikie' '81 gl1100I back on the lift, project with the step-son!

In The Shed:
'81 gl1100I barn find aka "Josie, the farmer's daughter." (almost comatose build)
'77 gl1000, roller parts bike.
'82 gl1100I, 'Old Crusty' titled roller parts bike (free!)
'82 gl1100I, My first 'Wing, and an expensive lesson!
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flyin900
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Re: Seal leak on rear end drive unit

#5

Post by flyin900 »

Thanks Track T,

It seems lack of lubrication or the correct type of moly on the splines is the culprit in most cases. I will definately keep that in mind if I have to go that route.
Current Bikes:

1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
1967 CL175K0 - Low production number with #802 engine serial- winter 2019/2020 full restoration.
1972 CB350F - Baby Four with low mileage - Cosmetic refresh to the next level 2021/2022.
1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
1984 CX650E - Restored summer 2017 - a rare Eurosport model - excellent one owner bike.
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Sidecar Bob
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Re: Seal leak on rear end drive unit

#6

Post by Sidecar Bob »

Lets not get started on using "moly" on the splines again. The FSM says to use lithium based grease "with moly additive". I've never used "moly" on the splines and at almost 140,000 Km they look like new. The key is aligning the splines in the wheel and the FD every time the wheel is off by loosening the FD nuts and then tightening the axle nut first, then the pinch bolt and the FD nuts last.
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Track T 2411
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Re: Seal leak on rear end drive unit

#7

Post by Track T 2411 »

"I have no special talent. I am only passionately curious." - Albert Einstein

"He that is good with a hammer tends to think everything is a nail" - Abraham Maslow

"If you can't take the time to do it right the first time, how are you ever going to find the time to do it over?" -Unknown

Current Rides:
'Grumpy' - '81 Standard, now fully dressed.
'Layla' - '81 Standard w/dealer installed fairing and Hondaline bags.
'Scarlett' '76 'Survivor' nekkid as a j-bird!

Under Construction:
The 'Jalopy' '78-'79 Mash-up
'Quikie' '81 gl1100I back on the lift, project with the step-son!

In The Shed:
'81 gl1100I barn find aka "Josie, the farmer's daughter." (almost comatose build)
'77 gl1000, roller parts bike.
'82 gl1100I, 'Old Crusty' titled roller parts bike (free!)
'82 gl1100I, My first 'Wing, and an expensive lesson!
New2U Bike? Read Me.
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