I'm sure this horse is dead... another driveline question - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Suspension - Brakes - Steering
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 04-30-2008, 09:18 PM
Slomotion34's Avatar
Registered User
 

Last journal entry: Mini Tubbing a 1967 Firebird Convertible Part 1
Last photo:
Join Date: Dec 2007
Location: Braselton, GA
Posts: 110
Wiki Edits: 0

Thanks: 4
Thanked 1 Time in 1 Post
I'm sure this horse is dead... another driveline question

It seems like this project has turned into a maze... and I am hitting every wall. I get sidelined from one part of the car and start on another, just to hit another wall...

I measured my driveshaft angle and here's what I got....

The transmission is at 2 degrees down, the rear is 2 degrees up (measured at the yoke). The driveshaft will be at a 10 degree (roughly measured) angle. If I run a line straight out from the transmission shaft to the rear, it's approx. 5" above the yoke for the rear (center of the yoke). According to an earlier post about this, I should take the sine of 3 degrees (.05234) and multiply that by my driveshaft length (Which I don't know, but the total distance is 36" from the back of the tailshaft to the yoke) that will give me the maximum offset that the u-joints can handle. Well, that is 2.09" for a 40" driveshaft, and I think I am in trouble. I can feasably lower the engine/tranny 1" by lowering the mid plate and making some new front plates, and I can raise the rear by another 1" by getting lighter weight springs for the coil-overs (I overestimated the weight of the rear of the car and the shocks are about 1" higher than they are supposed to be), but that doesn't put me in the range I need to be. Am I stuck trying to get some CV jointed driveshaft to work or is there light at the end of the tunnel that isn't another freight train?

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 04-30-2008, 11:52 PM
Registered User
 
Last wiki edit: Mopar tapered axle rear brake conversion
Last journal entry: What I'm doing now...
Last photo:
Join Date: Jan 2002
Posts: 4,267
Wiki Edits: 49

Thanks: 0
Thanked 4 Times in 4 Posts
Rule of thumb..... when the transmission output shaft centerline and axle input shaft centerline are parallel, the u-joint operating angle permissible is the length of the driveshaft divided by five.

Example: A short coupled driveshaft with a 15" length would be limited to 3 degrees maximum operating angle. A 36" shaft would be limited to 7 degrees, etc.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 05-01-2008, 09:59 AM
Slomotion34's Avatar
Registered User
 

Last journal entry: Mini Tubbing a 1967 Firebird Convertible Part 1
Last photo:
Join Date: Dec 2007
Location: Braselton, GA
Posts: 110
Wiki Edits: 0

Thanks: 4
Thanked 1 Time in 1 Post
Quote:
Originally Posted by Centerline
Rule of thumb..... when the transmission output shaft centerline and axle input shaft centerline are parallel, the u-joint operating angle permissible is the length of the driveshaft divided by five.

Example: A short coupled driveshaft with a 15" length would be limited to 3 degrees maximum operating angle. A 36" shaft would be limited to 7 degrees, etc.
I'm not trying to be argumentative here, so please don't take it that way (Because I need and appreciate the help - sometimes ideas have to bounce against my skull a few times before the light bulb turns on (However dim)).

That being said - every single thing I have read (and some even have pictures) have beaten the drum of 3 degree maximum on u-joint angles as an unchangeable factor. Most articles promise apocalyptical failures (actually just vibrations and early u-joint failures) if the sacred 3 degree line is crossed. This is where I am having trouble - the u-joint doesn't care if the driveshaft is 6 inches or 6 feet, the operating angle should be less than 3 degrees, right? Longer driveshafts only allow for more misalignment distance, not angle. I had to revisit what sine actually was, and it seems to be the appropriate way to figure the total distance of misalignment over a certain length.

The way I am figuring it, with my driveshaft at 10 degrees (this is an estimate - I measured 12 degrees one time but it's all handheld guestimating due to the fact that it's so far from being in the zone). For easy math we'll stick to 10. With the transmission down 2 degrees and the rear yoke up 2 degrees, I have met the criteria for being parallel. Now the math in my head tells me that 2 degrees down from the transmission means that that u-joint will be operating at an 8 degree difference from the driveshaft and the driveshaft will be at 8 degrees difference from the rear yoke. If the driveshaft is actually at 12 degrees, this puts the angle at 3 times the allowable offset, right?

This is the latest tangle in the web.... see, if I have to move the engine and transmission, that will affect where my floor will be. Thankfully, I haven't even started on that.... So far everything seems to be telling me that my chassis is pretty much screwed as far as the driveline goes. See, I can't put the floor in until I get this straightened out. I cant straighten this out until I can put the full weight on the rear of the car to load the springs, which means I need a floor so I can install everything in the car.

I think through all of this I am beginning to see why people buy turnkey rods. Sure the pride of going through 9 kinds of hell and being able to say "I did this" is one thing, but spending years learning how to become an automotive engineer before you can actually enjoy the car is making the other option actually seem like a good choice too....

Again, I appreciate the help, and I am just trying to understand (and avoid having to pay $600 for a cv jointed driveshaft, or go pay for another front motor plate and hack up my existing mid plate, cut out the transmission mount, buy new shorter coil over shocks, etc).
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 05-01-2008, 07:26 PM
Registered User
 
Last wiki edit: Mopar tapered axle rear brake conversion
Last journal entry: What I'm doing now...
Last photo:
Join Date: Jan 2002
Posts: 4,267
Wiki Edits: 49

Thanks: 0
Thanked 4 Times in 4 Posts
Not to worry, if you ask 10 people about driveline angles you'll get 15 different opinions.

I think you're over thinking this a little. If "U" joints had a max operating angle of just a few degrees then most of the 4x4 trucks out there wouldn't be on the road. As a matter of fact many RWD vehicles run a driveshaft angle between 5-7 degrees from the factory.

It looks to me, based on your post that you currently have a "U" joint operating angle of about 8 degrees which for a 36" driveshaft is very close to to the "rule of thumb" I quoted earlier. If you drop the trans 1" that should increase you're "U" joint angle by at least a degree to 3 degrees down and if you match that in the rear (3 degrees up) your "U" joint operating angle will be 7 degrees which is what the "rule of thumb" suggests for a 36" driveshaft.

To figure you're effective driveshaft angle you subtract the rear "U" joint angle from the front "U" joint angle which in this case give you an effective driveshaft angle of zero. You get zero because of driveshaft phasing. If you're driveshaft is phased correctly the "elliptical" movements will pretty much cancel each other out. If it's not then it will multiply the elliptical movement.

Remember that a "U" joint operating angle of 7-8 degrees is pretty small and most 4x4's run a lot more than that with no problems. The most important thing is to have the two angles (trans and pinion) as close to equal as possible.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 05-01-2008, 08:50 PM
powerrodsmike's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Make a fiberglass fan shroud
Last journal entry: Next.. ..Bagging the king B (barge)
Last photo:
Join Date: Jan 2005
Location: gilroy, california
Age: 53
Posts: 4,108
Wiki Edits: 161

Thanks: 0
Thanked 3 Times in 3 Posts
With all due resect, I'm gonna be one of the 15 different opinions...

Every car I've ever dealt with that had a U joint operating angle greater than 5 or 6 degrees had vibration and wear issues.

8* operating angle on any driveshaft U joint is asking for trouble. Ive seen it cause vibration and U joint wear, , and had to fix it to make it right.

Put a double cardan at the trans, (look under most stock 4 wheel drive trucks and you will see a double cardan at the trans end of both driveshafts.)

This will effectively split the 8* you currently have into 2 ujoints operating at 4* each, and you can move the pinion up to make the driveshaft essentially a extension of the pinion. this will lessen the operatiing angles even further.


I know it works, I learned about it here on the HRBB and applied it on a customers car.

Here is the thread.

short driveshaft high angle ujoints


But don't take my word for it, read what the engineers at Ford wrote up for us.

https://www.fleet.ford.com/truckBBAS/non-html/Q14.PDF

And this one.

http://www.drivetrain.com/driveline_angle_problem.html

Later, mikey
__________________
my signature lines...not really directed at anyone in particular..

BE different....ACT normal.

No one is completely useless..They can always be used as a bad example
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 05-01-2008, 10:44 PM
Registered User
 
Last wiki edit: Mopar tapered axle rear brake conversion
Last journal entry: What I'm doing now...
Last photo:
Join Date: Jan 2002
Posts: 4,267
Wiki Edits: 49

Thanks: 0
Thanked 4 Times in 4 Posts
Yep, another opinion. What'd I tell ya.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 05-02-2008, 05:06 AM
OneMoreTime's Avatar
Hotrodders.com moderator
 
Last wiki edit: Health and safety in the shop or garage
Last journal entry: Yard Dog pic
Last photo:
Join Date: Jul 2004
Location: Washington State
Age: 69
Posts: 7,226
Wiki Edits: 3

Thanks: 38
Thanked 125 Times in 121 Posts
Thanks guys This is very useful to me...Might save me a tranny rebuild..

Sam
__________________
I have tried most all of it and now do what is known to work..
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 05-02-2008, 07:23 PM
Slomotion34's Avatar
Registered User
 

Last journal entry: Mini Tubbing a 1967 Firebird Convertible Part 1
Last photo:
Join Date: Dec 2007
Location: Braselton, GA
Posts: 110
Wiki Edits: 0

Thanks: 4
Thanked 1 Time in 1 Post
It looks like the double Cardan is the way to go.... even if it sounds like an English fashion accessory. I'm going to find a retailer somewhere. That little jewell is going to save me a lot of work, broken parts, and vibrations.

Gentlemen, thank you so much for the information and opinions.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 05-04-2008, 01:20 PM
OneMoreTime's Avatar
Hotrodders.com moderator
 
Last wiki edit: Health and safety in the shop or garage
Last journal entry: Yard Dog pic
Last photo:
Join Date: Jul 2004
Location: Washington State
Age: 69
Posts: 7,226
Wiki Edits: 3

Thanks: 38
Thanked 125 Times in 121 Posts
The dble cardan is stock on Cadillacs ..maybe one of those can be used..if You have a T400 trans the yokes will fit since the cads use the T400..

Sam
__________________
I have tried most all of it and now do what is known to work..
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 05-04-2008, 08:11 PM
Slomotion34's Avatar
Registered User
 

Last journal entry: Mini Tubbing a 1967 Firebird Convertible Part 1
Last photo:
Join Date: Dec 2007
Location: Braselton, GA
Posts: 110
Wiki Edits: 0

Thanks: 4
Thanked 1 Time in 1 Post
SWEET! I am using a TH400. Thanks!!! There is hope for this ol' heap yet!
Reply With Quote Quick reply to this message

Recent Suspension - Brakes - Steering posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
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:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
383 stroker 73monte Engine 11 05-07-2014 08:08 AM
supercharger.... 73monte Engine 16 07-24-2010 10:27 AM
Horse power Question 528 stroker ??? charger528 Engine 1 09-18-2007 12:58 AM
Ignotion Set-ups Native Gearhead Engine 8 11-29-2003 01:20 PM
nitrous 69BiRd Engine 2 11-28-2003 10:33 PM


All times are GMT -6. The time now is 03:12 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.