New bearings and seals in upper, shimming thoughts

[flipbro]

I recently bought a drive serial # 0b818134 that was remained at one point and had 1:50 gears put in. Any way it does not hold preasure so im going to replace seals and orings I also want to change all the bearings as they look like they are a little scored and blueing the gears look great! So my question is Iam using the same casing same gears just replacing the bearings would i really have to reshim. could i not just put the orignial shims back in the way it was built and check the rolling torque? this is just a thought that it was shimmed rite when rebuilt be4 so why would it change?

 

[achris]

Re: New bearings and seals in upper, shimming thoughts

Checking shimming is essential when replacing bearings, gears or housing. No exceptions.

Chris....

 

[flipbro]

Re: New bearings and seals in upper, shimming thoughts

Ok chris Fair enough I watch your you tube vids and have picked up a lot of great info from you! Could you please explain what may change with just a bearing change? Are bearings not made to spec? There 4 should things not stay the same with the orignal shims? I am not arguing the fact with u as you have much more experiace as i. Just looking to understand things a little better. Thanks!

 

[daydreamer1252]

Re: New bearings and seals in upper, shimming thoughts

flipbro

I am curious as to the reasoning for "must re-shim" too. Coming from an automotive background when only the bearing and race are being replaced the shimming remains the same. The bearings are HIGH PRECISION items the casings and housing (cast parts) are not. There are hundreds of cars on the road that I should have "re-shimmed" that have hundreds of thousands of miles on them that have not come back to me for bearing problems.

I would be curious to know when the units are disassembled and reassembled what is the difference (change) in the shim-pack thickness and what percentage of units there is actually a CHANGE.

 

[998cc]

Re: New bearings and seals in upper, shimming thoughts

Venturing a little out of my realm here, but it seems that there are two reasons: 1) is that tapered roller bearings require a certain pre-load and 2) accurate meshing of the gears is fairly critical. So you have two settings to verify/adjust here by shimming. Manufacturing tolerances of even a few tenths of a "thou" for bearing races and rollers can add up to the point of requiring re-shimming. Of course, normal wear over time will affect pre-load and meshing as well.
I remember my dad setting up many differentials in his garage workshop for his 4WD buddies. It was quite a process.

 

[NHGuy]

Re: New bearings and seals in upper, shimming thoughts

When you replace the bearing pack there are 12 or 13 pieces, depending on which setup, to be reinstalled. On later drives the parts are placed over the shaft and very gently torqued till they make 6 to 10 inch lbs of rolling torque. When you do your shims you are taking all those softly pressed bits and placing the drive gear within thousandths of an inch of it's exact spot.
Some of the earlier drives use a different method, but your drive serial number sounds later like mine. If you find a small spacer inside the one between the bearing cups the torque is 75 foot lbs stationary. A lot different!
Do it wrong and you mess up the whole drive.
If you have done lots of bevel gears you might be able do it with careful measurement. Problem is, when the cap is off the drive you don't have a reference for the driven gear since the drive cap locates it's top bearing.
Just get a shimming tool, they are online at Mercstuff for $47.95. I'd sell you mine but I plan to use it again.
Oh, and the best reason of all is, I can tell you that my drive needed different shims. When I changed the input shaft, I reused my bearings and only changed my shaft, o-rings and seal. I had to remove shims when I reassembled it.
So either measure it off, take a chance or get the tool.
Chris does this for a living, he knows what he is doing. Guy saves me money and aggravation all the time.

 

[NHGuy]

Re: New bearings and seals in upper, shimming thoughts

I just re read your original post, are you sure it's leaking at the upper seal? Make sure you need it before you do all that work.

 

[flipbro]

Re: New bearings and seals in upper, shimming thoughts

Lots of good points and I wasn't questioning Chris at all just looking to learn some stuff is all thanks.

 

[flipbro]

Re: New bearings and seals in upper, shimming thoughts

Yes pressure tested and it leaked at the yolk seal and the bearings look a little scored

 

[Bondo]

Re: New bearings and seals in upper, shimming thoughts

Yes pressure tested and it leaked at the yolk seal and the bearings look a little scored

Ayuh,.... How many of those bearin's ya plan on replacin',..??

Have ya priced 'em out yet,..??

After ya do,.... price out a new replacement SEI drive,......

 

[flipbro]

Re: New bearings and seals in upper, shimming thoughts

I can get all four bearings from local bearing supplier for 150. Yes I did price a Sei 645 pluse shipping and duty and tax Lilkly up around 900. Witch is still Lilkly cheaper. But hey if I did it that way I wouldn't get the experience doing it my self .The worst part is the speacal tools and the prices lol but hey who doesn't like having the tools to do any job that comes their way that's how most of use have equired most of the ones we have cheers

 

[achris]

Re: New bearings and seals in upper, shimming thoughts

With a drive housing more that 20 years old, can you guarantee there has been no distortion? Or that the bearing manufacture hasn't changed the specs of the bearing by just a few thou, to maybe save some money on manufacture... Or that someone before you hasn't changed something, maybe lost a shim?????

Chris....

 

[flipbro]

Re: New bearings and seals in upper, shimming thoughts

Only guarantee in life are taxes and death. Good point I'm going to buy the tools and do it properly! No sence cheaping out now!

 

[achris]

Re: New bearings and seals in upper, shimming thoughts

Only guarantee in life are taxes and death. Good point I'm going to buy the tools and do it properly! No sence cheaping out now!

:thumb:

 

[flipbro]

Re: New bearings and seals in upper, shimming thoughts

When I install the two bearings on the input gear could I put the gear in the freazer for an hour then warm the bearing with a heat gun shot a little wd40 on the inner race and slide it rite on since there is just .014 thou tolarince our would this affect something also same as the gear and bearings on the out put shaft same thing. I've done the crank bearings on my sleds this way with no probs. but they are not a tapered bearing

 

[achris]

Re: New bearings and seals in upper, shimming thoughts

When I install the two bearings on the input gear could I put the gear in the freazer for an hour then warm the bearing with a heat gun shot a little wd40 on the inner race and slide it rite on since there is just .014 thou tolarince our would this affect something also same as the gear and bearings on the out put shaft same thing. I've done the crank bearings on my sleds this way with no probs. but they are not a tapered bearing

Do it by the book. You have the book, right?

 

[flipbro]

Re: New bearings and seals in upper, shimming thoughts

yes i do! Just thought it would be a better way then a press! Just thinking.Wondering if it was ok to do or not.As stated ive done this on a couple sled cranks and the bearings slide on with little pressure..rollout always seamed fine after. Just a thought! I will stick with the manual. Iam a millwright by trade so we are always trying to do things a little different. I do have a press aswell 12 ton i assume is enough

 

[achris]

Re: New bearings and seals in upper, shimming thoughts

A one ton press would be enough.

 

[flipbro]

Re: New bearings and seals in upper, shimming thoughts

So Talked to a guy at Canadian bearing today and he crossed my timkins bearings numbers with Fersa they Are about 110 bucks for all four with races! He told me they are a better quality bearing then timkins. Any one heard of them from what I read they supply a lot of oem parts.

 

[achris]

Re: New bearings and seals in upper, shimming thoughts

When it comes to things like bearings, spark plugs, and the like. I almost NEVER buy from Mercruiser. They sourced them from someone else, so can I... AND save some serious coin in the process.

Example... Oil reservoir for the trim pump. Merc price - $180, Oildyne price - $60. Serpentine belt - Merc price $114, from a local car parts shop $54. Oil pan - Merc price $700, GM parts on line $154... I can go on, but you get the point. If Merc bought it from somewhere else, so should you. And don't forget iboats also has a lot of parts and tools that you save a lot of money on.

Chris....