Electrical Corner

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Tuesday, January 22, 2013

Little Something About Gears and Speed

** Updated 18Feb2013: New reference towards the end.

Intro 

Just wanted to point out a math calculation related to ring and pinion gears.


Few items to keep in mind

For one, every vehicle and situation is different.  There isn't a one size fits all unless you are a auto manufacturer and are planning to make money.

Second, there is math involved.

Finally, its not a bolt on application.  Get help if you never installed gears in a differential before unless you don't mind spending a lot of time figuring it out and/or costing money in potential damage to your vehicle if the install isn't done properly.

So back to the math...the main reason I wanted to post this.  Two scenarios:

(1) a vehicle with 3.73 gear ratio doing 2000 rpms

(2) a vehicle with 4.11* gears ratio doing 2000 rpms
* lower gear (higher numeric value) than the 3.73 gear

To get the drive wheels/ring gear rotation per minute.

RPMs / Gear Ratio = Rotation per minute

So from the two scenarios above:

(1) 2000 / 3.73 = 536.2

(2) 2000 / 4.11 = 486.6

How about another:

(1) 3500 / 3.73 = 938.3

(2) 3500 / 4.11 = 851.6

Extreme gear:

(1) 4000 / 8.00 = 500

(2) 4000 / 3.27 = 1223.2

As you can see from the calculations, the gear used affects the rotation of the drive wheels moving the vehicle.  So, although you will gain more torque installing lower gears (high numeric values) your speed will decrease when compared with higher gears.  Assuming you have not change anything with the engine, your overall top speed will decrease.  This varies from vehicle to vehicle as not all vehicles have the same red line.  HINT: don't ride the line due to engine wear and potential damage.

Another example is the reverse gear vs forward gears.  The reverse is a lower gear ratio allowing faster acceleration, more torque (only have one reverse gear) but lower top speed before you get to the red line of the engine.

When determining a gear upgrade keep in mind that the more gear, the less top speed, but the more torque you will gain giving an increase in acceleration to the top speed of the vehicle, all limited by the ability of the engine.

Reference:
Car Gears Explained End-to-End Video
Car Craft: All About Axle Gears


Disclaimer: I'm not a gear pro.  I only know what I know.  So be sure to do your own research before making a decision.  I just wanted to share what I learned and put out there simple calculations to show the difference with changing gears.


Sunday, January 20, 2013

Adjustable Lower Control Arms Replacing the Cam Bolts (TJ Jeep)

Intro

During a recent install of a 4" lift, I installed new lower adjustable control arms all around.  During the uninstall of the front, I ran into a problem with frozen hardware.  I ended up cutting the stock control arms and bolts out with an angle grinder and having to purchase new hardware (see below for details).  Saving money, but getting the best there is, I stayed clear of the stealership as they wanted $20+ per bolt/nut/washer set and went to a local hardware vendor.  You should also know, going to the stealership was only going to replace the stock cam bolts with new cam bolts.  This was another problem as the cam bolt washers are known not to hold their position well when adjusted for an alignment.  Also, having adjustable control arms, cam bolts are no longer required for alignment.

New bolt and washer used
Notice the cam bolt tabs on the control arm


* The adjustable control arms are set to the shortest possible setting in order to set proper alignment on my Jeep.

Parts

  • Adjustable Control Arms [JKS in my case]
  • Cam Bolt Eliminator Kit (a set of four heavy duty steel, zinc plated washers that fit perfectly) [part # PPM-8114]
  • New bolts, nuts, & washers (went to Fastnels)
New Hardware picked up

** All are grade 10.9.

Front Lower Arm, Axle Side
  • Bolt - Hex Head, M14 x 2.00 x 110 
  • Nut - M14 x 2.00
  • Washer - in the cam bolt eliminator kit 
Front Lower Arm, Frame Side
  • Bolt - Hex Flange Head, M14 x 2.00 x 100
  • Nut - M14 x 2.00
  • Washer - if not using flange head bolts
Rear Lower Arm, Axle Side
  • Bolt - Hex Head, M14 x 2.00 x 110 
  • Nut - M14 x 2.00
  • Washer - in the cam bolt eliminator kit 
Rear Lower Arm, Frame Side
  • Bolt - Hex Flange Head, M14 x 2.00 x 100
  • Nut - M14 x 2.00
  • Washer - if not using flange head bolts
OVERALL Hardware count:
4 @ Hex Head, M14 x 2.00 x 110
4 @ Hex Flange Head, M14 x 2.00 x 100
8 @ M14 x 2.00 nuts
1 @ cam bolt eliminator kit (4 HD washers)

The Install

With the vehicle on the ground I started to remove one of the lower control axle end nuts and bolts to replace the small washers with the new heavy duty washers.  I soon found that the weight of the vehicle was pushing the control arms forward into the mounts, too far into the mount to place the new washer in position and be able to slide the bolt through.

So, I did this....

Using two ratchet straps I pulled the axle towards the front of the vehicle by wrapping the straps around the front bumper and around the axle on the passenger and drives side in order to keep the axle even.   Worked perfectly!

Passenger side ratchet strap



Driver side ratchet strap





pics of hole centered.....



pics of control arm bolted with washers in the tab space





After doing this you should realign your vehicle.  This is a simple process you can do yourself or pay someone to do it for you.  Being my Jeep's alignment is simple, I do it myself.  Haven't had any problems  with death wobble, tire wear, drifting, etc.  Plus its good to know how to do this if you wheel being it needs to be done often.  The steering wheel and toe are simple.  With a tape measure, a friend, and a few wrenches/sockets they can be done quickly.

Few references for alignment:
The End-all, Be-all TJ Alignment thread
Basic Jeep Front End Alignment
TJ Toe-in Alignment

Friday, January 11, 2013

CV Ball Assembly (Jeep TJ)


I found myself having a loud squeak when driving that was progressively getting worse with time.  Without going into the details of the symptoms I realized I was experiencing angry sparrows.  Do a search on the Web and you'll find plenty of examples and info.  Here I'm going to tell you a few things about my experience to shed some additional light on the subject.

First, the sound itself is exactly like the name, a bunch of birds going at it angrily.  It was coming from my front drive shaft.


Second, the cause was with the double cardan cv ball assembly that sits in between the two u joints in the H yoke.  And I found it goes by many names depending on who and where you are talking with/looking.

Here's the names I found:
  • CV Ball Assembly
  • Centering ball
  • Ball centering assembly/kit
  • Cross yoke
  • Centering yoke
  • CV centering yoke
  • Double Cardan Joint Ball Seating Kit
  • Double Cardan (CV) Centering Yoke
  • CV Socket Yoke



Third, having a ball joint press made pressing out and in the new u joints incredibly easy.  Much better than a hammer, socket, and general c-clamp.  I rented one for free from the local auto part store ($100 set normally.)

Forth, never, ever, I repeat, never try to repair the cv ball assembly by buying a CV ball repair kit.  Its not worth the pain and time.  There are no real tools for doing this easily.  I've read posts from drive shaft shop experts telling stories of how easy they use to do it then explain how they work on dozen of these things a week.  The biggest pain I found personally, and from people online, was with the brace for the ball.  It seizes to the cv ball  base.  (Pics coming soon as was in the middle of making this mistake.)


CV Ball Assembly Spring
 (Be care when removing the CV Ball Assembly.  This will fall out easily)


Two of the ~28 needle bearings in the ball



The drive shaft pin and seal that sits in the middle of the H yoke (double cardan) before it was cleaned up



The drive shaft pin and seal that sits in the middle of the H yoke (double cardan) after it was cleaned up



Here's the front drive shaft after pressing in the new Spicer u joint and re-installing on the Jeep.


P.S. if you jump ahead of what I wrote here and buy the part, don't trouble yourself with getting a greasable cv ball assembly.  Its incredibly difficult to grease it even with the needle adapter for the grease gun,  It sits in the middle of the H yoke between the two u joints.

Some part details:

SPI-211544X : Stock nongreasable CV assembly replacement by Spicer
2-86-418 : Seal for the nongreasable CV assembly (sits on the driveshaft pin; see pics above)
SPI-5-153X : Spicer greasable U-joint
617 (Advance Auto parts) : Moog repair kit for the nongreasable CV ball assembly
NEA-7-0081 : Neapco repair kit for the greasable CV ball assembly (not stock; only if upgraded)

 ...more to come in the week ahead