Bronze gear bushing clearance - Page 5 - Alfa Romeo Bulletin Board & Forums
 8Likes
Reply
 
LinkBack Thread Tools Display Modes
post #61 of 70 (permalink) Old 02-04-2018, 02:32 PM Thread Starter
Registered User
 
goats's Avatar
 
Join Date: Jul 2006
Location: san diego CA
Posts: 5,074
Here is what happens if first gear is too tight. I set it to about 1 to 1.5 thou— it rotated cleanly with oil and I thought I was good to go. Lesson — tight tolerances can be TOO TIGHT!!!

Result— had to pull trans out, crack it open and now fighting with mainshaft and tripod placement.
Attached Images
 

74 GTV with 10548's and Ingram pump
71 Spider 1750 BOMBER ; 1995 LS 78K tight fast car
goats is online now  
Sponsored Links
Advertisement
 
post #62 of 70 (permalink) Old 03-08-2019, 08:38 PM
Senior Member
Gold Subscriber
 
1750GT's Avatar
 
Join Date: Nov 2005
Location: Oakville, Canada
Posts: 3,352
Garage
I am going through a transmission rebuild and want to check the radial clearances between the gear bushings and the mainshaft. It seems the most accepted limits area the following;

1st - .0049"-.0067"
2nd -.0037"-.0055"
3rd - .0026 -.0042"

Are the limits above supposed to be radial or diametral clearances?

When I measure my gears, I get the following results;

1st - bushing I.D = 1.3785"
shaft O.D. = 1.3725"
clearance = 0.0060"

2nd- bushing I.D = 1.3795"
shaft O.D. = 1.3735"
clearance = 0.0060"

3rd - bushing I.D = 1.3780"
shaft O.D. = 1.3755"
clearance = 0.0025"

cheers


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


1971 1750 GTV 105.48 (sold), 1972 1300GTJunior (sold)
1969 1750 GTV 105.5 , 1972 Montreal
1750GT is offline  
post #63 of 70 (permalink) Old 03-08-2019, 08:58 PM Thread Starter
Registered User
 
goats's Avatar
 
Join Date: Jul 2006
Location: san diego CA
Posts: 5,074
Diameter. Personally I would not use anything more than 3.5 thou and nothing less than 1.5 Ish. But that’s just my view. Don’t make first less than 1.5!!!

74 GTV with 10548's and Ingram pump
71 Spider 1750 BOMBER ; 1995 LS 78K tight fast car
goats is online now  
Sponsored Links
Advertisement
 
post #64 of 70 (permalink) Old 03-08-2019, 10:30 PM
Senior Member
Gold Subscriber
 
Norseman50's Avatar
 
Join Date: Apr 2014
Location: Bellevue, WA
Posts: 1,447
Garage
Quote:
Originally Posted by goats View Post
Here is what happens if first gear is too tight. I set it to about 1 to 1.5 thou— it rotated cleanly with oil and I thought I was good to go. Lesson — tight tolerances can be TOO TIGHT!!!

Result— had to pull trans out, crack it open and now fighting with mainshaft and tripod placement.
Bob,

Did you secure the dimpled bronze bush to the gear with any Loctite when you pressed it into place (prior to honing it out)?

Edward
'88 Quad - "Claudia"
Norseman50 is offline  
post #65 of 70 (permalink) Old 03-08-2019, 11:11 PM Thread Starter
Registered User
 
goats's Avatar
 
Join Date: Jul 2006
Location: san diego CA
Posts: 5,074
I really don’t remember. If I did it was locktite green but I truly don’t recall for certain — Richard says nonloctite as it can expand —

Bob

74 GTV with 10548's and Ingram pump
71 Spider 1750 BOMBER ; 1995 LS 78K tight fast car
goats is online now  
post #66 of 70 (permalink) Old 03-09-2019, 05:47 AM
Senior Member
Gold Subscriber
 
1750GT's Avatar
 
Join Date: Nov 2005
Location: Oakville, Canada
Posts: 3,352
Garage
Quote:
Originally Posted by Top Down View Post
I have now seen an original Alfa Romeo spec sheet from 1989 covering these tolerances. They state:

1st .008 - 0.012
2nd and 3rd .005 - .008

So if its good enough for original build its good enough for me.
What document is showing these as wear limits? I ask because these limits would indicate that my gears would be good to go!

Whereas the wear limits in post #62 tells me that I'm only 7/10 of a thou under at the upper limit on 1st , 1/2 thou over on 2nd and 1/2 thou under on 3rd.

From the few accounts I've read on this thread.....reaming/honing new bushings might be an issue and unecessary in my case.


.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


1971 1750 GTV 105.48 (sold), 1972 1300GTJunior (sold)
1969 1750 GTV 105.5 , 1972 Montreal

Last edited by 1750GT; 03-09-2019 at 05:58 AM.
1750GT is offline  
post #67 of 70 (permalink) Old 03-09-2019, 07:15 AM Thread Starter
Registered User
 
goats's Avatar
 
Join Date: Jul 2006
Location: san diego CA
Posts: 5,074
Well there is that consideration too. It is a true hassle to replace the bushings. I did it both times because I wanted the trans as perfect as possible, and I wanted the experience.

I agree that if you are out of spec it’s by a hair at most. A lot of this is feel too — if your wear remains concentric and truly non offset, I’d probably ( at this stage in my life) leavecem alone. If you are not racing etc I would be happy enough I suppose just cleaning and reassembling as-is. Really a judgement /time/ resources /hassle factor call.

I would NOT criticize or suggest otherwise if you were to leave as is. Pretty gray area unlike an oil pump that’s out of tolerance!!

74 GTV with 10548's and Ingram pump
71 Spider 1750 BOMBER ; 1995 LS 78K tight fast car
goats is online now  
post #68 of 70 (permalink) Old 03-09-2019, 10:14 AM
Registered User
 
Top Down's Avatar
 
Join Date: Aug 2016
Location: West Sussex UK
Posts: 167
Quote:
Originally Posted by 1750GT View Post
What document is showing these as wear limits? I ask because these limits would indicate that my gears would be good to go!

Whereas the wear limits in post #62 tells me that I'm only 7/10 of a thou under at the upper limit on 1st , 1/2 thou over on 2nd and 1/2 thou under on 3rd.

From the few accounts I've read on this thread.....reaming/honing new bushings might be an issue and unecessary in my case.


.
Now that might not be so easy to find! At the time I would have been scouring the internet for information, once recovered and used I didnt keep a reference, my bad. I'll have trawl through some folders to see if I did keep it.

PS. I do recall the source now. It was a photo of a workshop manual which I was sent by Ian Ellis who is a well known Alfa specialist here in the UK. I have found my email to him, thanking him for the information, but not the email to me.

Daily drive is a Giulia 2.0 MA, wife drives a 939 Spider in the summer and a 1.6TS 147 in the winter. For special sunny days we have a S2 Spider Junior in the garage.

Last edited by Top Down; 03-09-2019 at 11:41 AM.
Top Down is offline  
post #69 of 70 (permalink) Old 03-09-2019, 02:25 PM
Senior Member
Gold Subscriber
 
Norseman50's Avatar
 
Join Date: Apr 2014
Location: Bellevue, WA
Posts: 1,447
Garage
Quote:
Originally Posted by 1750GT View Post
I am going through a transmission rebuild and want to check the radial clearances between the gear bushings and the mainshaft. It seems the most accepted limits area the following;

1st - .0049"-.0067"
2nd -.0037"-.0055"
3rd - .0026 -.0042"

Are the limits above supposed to be radial or diametral clearances?
Diametrical.

Quote:
Originally Posted by 1750GT View Post
When I measure my gears, I get the following results;

1st - bushing I.D = 1.3785"
shaft O.D. = 1.3725"
clearance = 0.0060"

2nd- bushing I.D = 1.3795"
shaft O.D. = 1.3735"
clearance = 0.0060"

3rd - bushing I.D = 1.3780"
shaft O.D. = 1.3755"
clearance = 0.0025"

cheers
At the present time, after rebuilding a couple of Alfa Romeo 5-speeds (in which I replaced these gear bushes and struggled to find a competent enough machinist to broach them out to 0.002" over the mating shaft diameters), and having discussed this clearance question with a Mechanical Engineer who designed transmissions for Chrysler Corp. during the 70's and '80's (and now owns a European Transmission repair shop in Seattle), I have come to the conclusion that a clearance in the 0.002" to 0.006" range for any of these gears is suitable, and I would even reuse one with a 0.007" clearance before going to the trouble of pressing out an old, and then pressing in and honing out a new dimpled bronze bushing.

However, if I owned (or had access to) a top quality lathe, I'd modify a set of 10" Full Grip Tongue & Groove Aluminum Lathe Soft Jaws (4" HT, 10" Pie Diameter) that would allow me to secure these gears with negligible run-out and then I'd be able to broach out new internal bushes to ten-thousandths tolerances.

Bottom line is, I'd just re-use your gears with your present clearances, and not fuss with replacing the internal bushings.

Good luck,

Edward
'88 Quad - "Claudia"
Norseman50 is offline  
post #70 of 70 (permalink) Old 03-09-2019, 09:02 PM
Senior Member
Gold Subscriber
 
1750GT's Avatar
 
Join Date: Nov 2005
Location: Oakville, Canada
Posts: 3,352
Garage
Quote:
Originally Posted by Norseman50 View Post
Diametrical....... I have come to the conclusion that a clearance in the 0.002" to 0.006" range for any of these gears is suitable, and I would even reuse one with a 0.007" clearance before going to the trouble of pressing out an old, and then pressing in and honing out a new dimpled bronze bushing.Bottom line is, I'd just re-use your gears with your present clearances, and not fuss with replacing the internal bushings.
Good luck,
Yeah that's what I'm going to do for now. It's going to be a little loose I'm sure.....but I need to get the car completed by Spring this year! So if the tranny turns out to be too problematic or noisy...I'll replace everything on the next rebuild...bearings & bushings.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


1971 1750 GTV 105.48 (sold), 1972 1300GTJunior (sold)
1969 1750 GTV 105.5 , 1972 Montreal
1750GT is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Alfa Romeo Bulletin Board & Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome