Trans Output Flange

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Trans Output Flange

Post by Seth » Thu Feb 22, 2018 6:48 pm

I'm trying to replace the seal on the output flange of a 75 R90S.
I have the Cycleworks puller.
Got the nut off, but the flange is on real tight.
I have a long pipe on the tool handle so I don't have to hold it.
Using a 1/2" breaker bar. Putting a lot of torque on it.
I'm afraid of breaking something.... either the bolts on the flange or the flange itself.

Haven't tried heating it, but that's a little tough because the tool blocks the flange.
Would have to heat it before bolting on the tool.

Any suggestions? Any experience with the amount of torque required?
What about using an impact gun on the drive bolt?

Thanks in advance.

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Re: Trans Output Flange

Post by Rob » Thu Feb 22, 2018 7:21 pm

I'm thinking it might be a two-person job...


source (good read):
Rob V

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Re: Trans Output Flange

Post by Seth » Thu Feb 22, 2018 7:58 pm

I had read that site before.
I'm using a galvanized pipe to extend the handle of the puller handle.
The other end of the pipe was inserted into the trailer hitch of my pickup, so I'm hoping I don't need another person.
Guess I'll need to put another pipe on my breaker bar.

One thing I've not done which I should have is greased the threads of the puller's drive bolt.
Thought of it before writing my post.

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Re: Trans Output Flange

Post by Beemerboff » Thu Feb 22, 2018 9:17 pm

I have a alloy puller which cost less than %10- on ebay.
Doesn't look as if it would pull the top of a beer bottle, but I just tighten it up to around 50 ft/lbs then give the center bolt a sharp wrap with a 3 1/2 lb hammer and it has never failed to remove the flange.

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Re: Trans Output Flange

Post by Seth » Fri Feb 23, 2018 3:56 pm

Got the flange off.
I had left it overnight tensioned on the puller, not that it had anything to do with it.
Yesterday, I had hit the puller pressure bolt with my hand sledge, but the trans was not on a solid surface.
I moved it to a couple of 4x4's on the concrete floor. A good strike with the sledge and it came off.
Replaced the seal and put it back together.
Thanks for the support.

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Re: Trans Output Flange

Post by tsa » Fri Feb 23, 2018 5:17 pm

A word of caution; with the box on the ground, a good blow on the end of the output shaft applies force along the output shaft and via the frontmost bearing onto the inside of the gearbox housing - which isn't necessarily a good thing.

When I was about to finish rebuilding a trans that had suffered a snapped intermediate shaft (with both radial and axial stress via the front of the intermdiate shaft onto the recess for the bearing, I discovered that this sudden and brutal force had created a fracture line along the "home" for the bearing. I only noticed this when oil leaked out of the crack when I heated the housing to fit the shafts into the box again.

Hopefully your gearbox case is still OK!
'73 R75/5, '78 R80/7, '83 R80RT

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Re: Trans Output Flange

Post by Seth » Mon Feb 26, 2018 11:44 am

Well TSA, I think I broke the trans.

Went out this morning to check it out.
No external cracks showing, but it doesn't seem to shift right.
It will spin in first gear, but if I shift it up into any other gear, it seems to lock up.
I may take the back cover off to look what's going on, but I think I'll need to get another trans.

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Re: Trans Output Flange

Post by Wobbly » Tue Feb 27, 2018 8:28 pm

One of the shafts has to be spun continuously in order to get a non-synchronized gearbox (like a motorcycle uses) to shift. It doesn't have to be spun fast, but it does have to be moving.

Try that and see if things feel better.
After 20 years as a professional bike mechanic and 30 years as an engineer I know just enough to be dangerous !

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Re: Trans Output Flange

Post by Airbear » Wed Feb 28, 2018 12:13 am

I'll go even further and say that both shafts need to be rotated, just as they are in a moving motorcycle. When checking a gearbox I fit a clutch plate (with handle) to the input shaft, like this:


One hand winds the handle, another hand rotates the output shaft and a third hand (or other body part if you don't have a third arm or nearby accomplice) can shift the gear lever.
and Brunhilde - 1974 R90/6

Graduate, Wallace and Gromit School of Engineering and Design (Pending)

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Re: Trans Output Flange

Post by Seth » Wed Mar 07, 2018 10:04 am

I took the trans to Bob's BMW in MD, as they supposedly have a good reputation.
The tech disassembled, reassembled, the trans a couple of times and could not find the problem.
After 3 hours of this, he brought the trans back out to me, back cover removed, and showed me how the trans moved as in 1st gear even though the selector was in neutral. I pointed out to him that it appeared the distance between the 1st and 2nd gears seemed too tight, as the sliding gear on the shift fork couldn't disengage from both simultaneously. He had looked with a mirror and thought 1st was disengaged, but the sliding gear and 1st gear were moving in sync, locked together. The dogs on the sliding gear had no additional clearance on 2nd gear.

I'm not an expert on this and don't know what's supposed to maintain the distance between the 1st and 2nd gears so the sliding gear has enough clearance. The parts diagram shows a washer between 1st gear and the bearing. There seemed to be a bit of a gap on mine. It also shows the bushing and another washer.

Unfortunately, I left the trans with Bob's to continue work, asking them to check the assembly of these gears on the shaft, but feel if I (an uneducated person) saw this in 5 minutes after they didn't after 3 hours, maybe I should be going somewhere else.

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