Hello, I've got a 1992 Hijet Jumbo cab 4x4 that I've converted to electric drive. It uses an AC motor with the transmission locked in direct drive and stripped of all gears. The 4wd system is still functional but rarely used. With the lithium batteries it's using the maximum range looks to be about 60km in good conditions which is perfect for what I need it for but more is always better. Check out my blog here for some pictures; click the electric mini truck page at the top. http://jessetufts.wordpress.com/ In an effort to reduce drag I'm looking at using lighter fluids in the transmission, transfer case and both diffs. The transmission has no gears any more so it really just needs some light oil to keep the bearings happy. The transfer case is also direct drive when in high so there are no loaded gear meshes unless it's in 4wd. The front diff doesn't even spin unless the axle is engaged and is rarely used but the axles turn constantly. The rear diff is of course spinning all the time and is loaded. So I'm thinking I could use something like synthetic ATF in the front diff and transmission/t-case to keep the bearings lubed and provide some protection for when it is in 4wd, but does anyone have any experience running lighter weight oils in the rear differentials of these trucks or any trucks? Has anyone ever had a rear diff failure? If the diff is going to last 1,000,000 km with standard gear oil I would be happy to have it wear out after 200,000km if running ATF gave me an extra 10km of range. That would be 10+ years of driving and I don't think the rest of the truck will last that long! Regardless I am going to do some tests to figure out the total drive train power losses, I just block it up, put it in 4wd and spin the wheels steady state at different speeds. My amp draw x voltage gives exact power losses to just turn the drive train. Other ideas include lighter grease for the front CV joints. What do you think? How else could I reduce parasitic drag on these trucks? Cheers, Jesse P.S. these trucks make awesome conversions, lightweight, easy to do and a blast to drive!
aerodynamic drag should be a big consideration as well..if you don't use the truck off road and with no int.combustion engine heat and exhaust to worry about..a full under belly pan would reduce wind resistance considerably...There was a "mythbusters " episode where they examined a dimpled golf ball surface on a car and found that aerodynamic drag wag also greatly reduced..possibly there is a textured vehicle wrap than can be used to the same effect..I'm sure you have figured out low resistance tires and pressures,but slightly out of spec alignment can cause parasitic drag...lighter rims/tires (unsprung mass) could also use less power to accelerate.....the higher torque of the electric motor may in fact make the stock viscosity diff/transfer case fluids necessary..vehicles with more torque generally(but not always)use higher viscosity fluids in drivetrain components due to increased shear pressure.....cool project by the way
Well up till about 50km/hr rolling resistance and aerodynamic drag are about equal generally and considering this is generally a pretty low speed truck I thought I would tackle the rolling drag first. A belly pan is an interesting idea, but the transmission/ transfer case on these trucks hangs down below the frame quite a bit which would make things difficult. Could be worth a try though. The golf ball dimples, well, not going to happen. What they do is trip the air flow around the vehicle from laminar to turbulent flow which has the effect of keeping the boundary layer attached further down the backside of the roof-line which reduces the size of the low pressure wake, reducing drag....... might be worth it if I didn't have a flat back of the cab negating any of the benefits. Probably removing the headache rack would help as would a tapered cap for the bed. Our motor does have more torque but it also has no vibration and no dropped clutch takeoffs, so it should be easier on things actually. We're also locked in 5th gear so there is no torque multiplication from the transmission. All good ideas though, Thanks! Jesse
yeah the dimpled thing I threw in at the last minute,but you're right especially at lower speeds it wouldn't really be helpful....Yes you are locked in 5th and no clutch but you still have the torque from the motor being transferred to the non-moving differential when taking off from a stop..If you wanted to experiment ..as long as you used gear oil you could use a lighter synthetic and check the fluid after a month for metallic particles in the fluid..if nothing then go a bit lighter again...lol the headache rack didn't even cross my mind..prob. a good bit of drag
I have a 92 hi jet as well. I switched the diff's, transmission and transfer case to a synthetic transmission/hydraulic oil 3 years ago. This oil has the same flow characteristics as a 0-40 motor oil. this is an Ag/industrial oil. The most noticable difference is in cold weather. I use the truck daily in the winter months and it behaves like it is summer. Vern
I suppose if I wanted to get really scientific I could get fluid analysis done on the oil but keeping an eye on the colour and the magnets should do it. First hand experience! Excellent. Do you know if the oil you used is Api Gl-4 or Gl-5 rated? Or if you give me a name I can look it up. Synthetic for sure will be worth it, the amount of oil in these trucks is pretty small so it's not much of an expense! Thanks, Jesse
The oil that I used is Co-op Super T-HF SL from Federated Co-ops. It meets the GL ratings of the major equipment manufacturers. Most of the newer equipment use a common oil for the transmissions, differentials and hydraulic systems, so needless to say if it can handle the 500+ horsepower in these 4wd tractors it can handle what ever these little guys can throw at them. Check with the ag or construction equipment dealers in your area. If I recall I only used 4 or 5 litres to do the truck. Vern
