Project BMP

Page 26

   
 
 

Round 2

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Just when I thought the fabrication was complete along comes another opportunity: the chance to buy some setup Dana 60's.  At first I thought I'd buy them and hold them till this winter before swapping them in.  Then I realized now is the best time to do the swap while all of my existing Toyota axle parts are still fairly new and unbroken. There were a couple other reasons why I decided to go ahead with the swap: better turning radius, wider stance and the obvious heavier construction of the Dana 60 running gear.

The first step was to part out my existing axles.  I made a list of all the parts on the buggy as well as all the spare parts I had and posted them to a few internet forums I frequent.  The response was pretty amazing, I had all the big stuff sold within a day, and most of the smaller stuff went during the next week.  During the next week I packed and shipped the parts to their new owners as payments came in. By the end of the second week I had sold approx. $3000 in parts and the new axles showed up on a friends trailer.

The new front axle is a 1978 Chevy Dana 60, narrowed to 61" (measured between the wheel mounting surfaces), shaved (providing another 1.75" of ground clearance), with 5.13 gears, ARB locker, 35 spline outers and hi-steer arms.  Not sure if I am going to use the hi-steer arms until I can mock up the steering ram. Interestingly the distance from the knuckle "C" on the D60 axle is the same as the distance between the knuckle balls on the 85 Toyota axle housing, the extra width of the 60 is due to the bigger knuckle/brake/hub assembly.  This means I should be able to have the same lower link mounts and shock mounts that my previous axle had, the only thing left to design is the axle bridge where my upper link mounts will connect and a place to mount the steering ram.

The rear axle is from a 78 Ford, full floater narrowed to 61",  shaved with 5.13 gears, a spool, 35 spline axles and disk brakes.  This axle should be even easier to setup compared to the front since there is already an axle bridge installed.  I still have to determine if I can re-use the upper link mounts on the bridge, new lower link mount tabs will be installed along with tabs for the swaybar. 

To adapt the drive shafts I will purchase some D60 to Toyota flanges, available from High Angle Driveline.  The replace the existing yoke on the pinion with a Toyota style flange allowing me to run standard u-joints without the weak u-joint straps which seem to be a common point of failure for rigs running them. 

Update 5-23-05 - Started on the axle swap this weekend. Thanks to Scott who stopped by. I wasn't expecting to have the axles last weekend so I wasn't as prepared as I wanted to be. To help cut thru this job faster and for future projects I broke down and bought a plasma cutter. It made removing the brackets pretty quick but there was still a ton of cleanup grinding which took a while.  I ended up removing 20 lbs. of old bracketry from the rear axle.  Had I known I was getting the axles last weekend I would have ordered the plasma cutter earlier and gotten a lot of the cleanup work done during the week.  Things still worked out pretty good, ordered the cutter on Monday, it arrived Thursday, spent Friday picking up a filter and some air line adapters to setup the unit and was cutting on Saturday morning.

The new toy, a Thermal Dynamics Cutmaster 51.

Rear housing almost ready for new parts.

We moved the front axle into position but nothing else was started.

Option 1 and 2, upper link on the axle end is moved up in second spreadsheet

I plugged in my suspension numbers into a 4 link analyzer (available here: http://home.earthlink.net/~triaged/Files/4BarLinkV3.0.zip) and played around with the settings for the rear suspension. Previously I had a pretty low roll axis which sloped downward. I believe I made my axle bridge too tall on the last housing (or should have moved the lower tabs up on the axle housing more). It works for Scott because his lower tabs are mounted on top of the housing, on mine they were below. Anyway, the new setup will have two options, by adjusting the upper link mounts on the axle end I can either have a flat roll axis or a gently rising roll axis with about 15% more anti-squat. Up front Scott helped me plug in some numbers and we found that by moving the lower links further outboard on the frame end the I could get a higher and flatter roll axis. We also adjusted the uppers on the axle end to drop the anti-squat to close to neutral with the ability to dial a little more in via the lowers on the frame end. I guess we'll see how good the theory in the spreadsheet works in the real world.
 

On Sunday I tried to get my uppers done, it took me a while to come up with something. Once I got rolling I made pretty good progress. I was able to install new upper link mounts on the frame end and place them closer to the axle so I could re-use my upper links (they were going to be 4" too short). I am pretty sure I can't do this for the front so new upper links will be needed there. Here's a couple progress pics. One holdup occurred late Saturday afternoon when we went to install the pinion flange adapter to hook up the driveshaft. We couldn't get the pinion flange off with my impact gun.  On Sunday I bought a huge pipe wrench to hold the flange and used my foot on the breaker bar with socket to turn the nut. It wasn't easy but it finally started moving and I got it off. I installed the Toyota to D60 flange and it looks like the rear driveline length is correct and no modifications are needed.


One thing I was worried about was running the 3/4" heims with these larger axles. The spreadsheet calculations put me right around a 4x safety factor which I felt was bare minimum (my heims are rated for 24k lbs radial load). I also don't have money in the budget to completely re-do all the links and their mounting point to use larger heim joints.  The solution is to go with a 3/4" heim joint that is rated higher but these are generally pretty expensive.  While browsing the PBB General 4x4  section I caught a thread that discussed 3/4" heim joints. An acquaintance who goes by the name "Purple Nerple"  pointed out a good place to get some affordable rod ends: http:\\www.rodendsupply.com . They sell the XM10-12 which is a 3/4" heim joint with a rating of over 40k lbs. Best part is they run $26.89. All of my lowers will be replaced with these, the uppers are seeing roughly half the forces according to the calculations so those will stay the same.
 

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