Monday, March 31, 2008

Rear Lift Kit Installed

This weekend we installed the rear lift kit - new leaf springs, U bolts, shackles, and shocks. First was the leaf springs. Getting them on was quite challenging - the front eye went on OK, but to get the rear eye installed, we had to:
  1. Jack the axle up to just the right height
  2. Pull the rear eye down with all my strength while...
  3. KatC installed the bolt through the shackle and eye.
But here is the passenger's side installed:

With the leaf installed, we next installed the shock. This was fairly straightforward. Here, KatC is tightening the bolt that attaches the lower end of the shock to the axle, while I bolt it to the frame:

With both leaf springs installed, and the tires put back on, we temporarily replaced the hood so that we could store the Jeep outside in inclement weather:

And here it is. It looks like the front is lifted too, but it is not. The lack of engine and transmission weighing it down has caused the springs in front to relax. They will be replaced, and then it will look even higher :-).

We have not yet torqued the rear springs down to specifications. I want to get a little weight in it first so that it is sitting at its natural tension point before I tighten the eyes, shackles, and U-bolts all the way down.


Anonymous said...

Hey Ross,
Glad to see that someone else is doing a Cherokee. I'm the reason that Mike Brown has a pattern for your transmission. I have about 1000 miles on a '96 2wd that I converted recently. AC55 system with a UMOC instead of DMOC. I'm getting only 20 miles on a charge and I think it is because of the only 1170 lbs of US battery flooded 12 volts. You should do better. One piece of advice: I'm pretty sure that you need to measure fron the CLUTCH SURFACE of the flywheel to the mounting surface of the engine block. The photo shows you measuring from the tone ring for the crank position sensor. My magic number was 1.415 inches and I had the same transmission. PLEASE double check your measurements before you order the adaptor. Feel free to ask me if you have any Cherokee specific questions or questions in general. I might also be able to help you with the clearance issues you will have with the motor and track bar.

Anonymous said...

Whoops sorry I meant starter gear not the tone ring.

Ross Cunniff said...

Thanks for the clue - I'll remeasure. Which US Battery model are you using? Do you have a website?

Anonymous said...

It was a 24 TM at the advice of the manufacturer. I'm seriously thinking of Optima D31s for the next pack. Sorry no website yet. I can send pictures if you like.

intergalactic said...

As a former Solectria employee, I might offer a few suggestions. Make sure the DMOC gets a source of cooling air that isn't recirculating underhood. Also, the stall torque drops quickly with heat sink temperature. Start in 1st gear and you will be happy.

Unless you really need it, why use 4wd? the power loss in the transaxle may disappoint you.

Also, battery thermal management (heat, lots of it) will help when the temp drops below 60F.

Finally. Be really careful with the higher pack voltage. I can't stress enough how different 312VDC is.

Ross Cunniff said...

Intergalactic, thanks for the tips. Regarding the air intake - the Jeep has an open front grill (since it used to have a radiator) - would that be enough fresh air intake? Should I worry about providing a hot air exhaust?

Regarding 4wd - because the Jeep already has it. To convert it back to 2wd will take a lot of hacking - new transfer case, new front suspension & steering system (no axle), possibly new transmission and driveshaft. A real pain. I guess one option would be to let the u-joints spin freely on the input of the front axle and the output of the transfer case, but I don't know if that is risking some sort of damage.

I've debated battery thermal management (my Porsche could also use it) - do you have any recommendations? I'll start doing some web research.

And, yes, finally on the 312V - I've been plenty impressed by the damage 144V can do (scroll to the bottom of that post). And I've gone to 4/0 cable based on voltage drop calculations - which gave me pause on the amount of energy involved here. I plan on quadruple-checking every step. One other thing I'm doing is designing the batteries as separate packs wired together in series with high-voltage high-amperage quick disconnects between them. This would mean that I could disconnect a pack to do maintenance on it at a much lower voltage (probably around 72V per pack or so). Of course, the quick disconnect is a possible point of failure. No free lunch...

intergalactic said...


This is a guess as to a jeep transmission. But an educated one, as this was my area of specialty at Solectria. I suspect you could put a 2WD system in the jeep and leave the steering and suspension alone with the u-joints at the wheel ends disconnected. But check with a Jeep specialist. I suspect you could trade a 4wd for a 2wd unit easily, or even make money. Money you might need for the different driveshaft. Or trade both.

The airflow on a DMOC is done with impingement. Blowing straight down perpendicular to the heatsink, and out both ends. Something as simple as plastic ducting to the inlet from the radiator grille or up by the windshield wiper tray (not the roaring hot air wafting up from the brakes.) and vent elsewhere. Routing the exhaust isn't as critical as having a discrete intake from the outside that doesn't recirculate the hot stuff. A 12V fan in the inlet isn't a bad idea as you need a cold heatsink the most when you are stopped in traffic on a hill on a hot day.

Two layers of heatshrink on the wrenches is a start. 600V *DC* rated fuses for everything that comes close to HV. 22 gauge wires will explode when shorted if unfused. Coating skin and eyes with molten copper.

Floodies are a bad idea. in my opinion. We used Gel batteries. The leaking electrolyte with floodies can short things to ground with 390V present when you are on the overcharge phase at 15V per battery module. Or any other time. Fuse the pack mid-string, or or in the middle of each group. Zivans are known to overcharge and dry out Gel batteries, or at least the 10 year old Zivans did.

I suspect a 250A fuse will do it, or a 300A so the 250 doesn't fatigue fail.

Don't use Anderson connectors. The SB50 and SB350 styles don't seal and if wet will short out and burn up. The connectors used for long welding cables or outdoor power supplies with the tapered rubber boots work well. Cam-Lok, I think.

I think you did well to use the transmission and the AC55 and DMOC445. For a single speed, You would have needed a DMOC 645, although that isn't something they would sell you.

Get good U-joints, you can use them well with regen on an AC55.

Hit me up again for thermal management. But the gist is: All batteries the same temperature is most important. Next goal is to keep them all warm.

Good luck,


P.S. hit me with a real e-mail for a gmail reply

Anonymous said...

It's the jeep guy again. The swap to 2wd is easier than you think. It does require the 2wd transmission and driveshaft, but those are relatively cheap junkyard items. The front axle from a 2wd is a bolt in item. The steering system is identical. Keep the links you have. The control arms, mounts and geometry are no different from the 4wd. The bonus is that this eliminates the front differential which gets in the way. I made my own, but I think there are straight track bars available which eliminate that bend and will not hit the motor as quickly. You can only do this with a 2wd axle. Another option would be to just pull the front axle and driveshaft and keep the transfer case and original rear shaft. This is heavy, but simpler than swapping the transmission (which is not that hard on the Cherokee) Come to think of it, you can call Mike Brown and see if he still has my transmission. It's a 4 speed out of a junkyard 2wd Comanchee that we used to make the adaptor, but you can have it for free plus shipping.
BTW, I second the motion on those welding connectors.
Seriously, e-mail me about the 2wd Cherokee stuff. I've got a lot more ideas that can help, but it gets long and complicated to explain here. I'd be happy to exchange phone numbers and talk a while.

Ross Cunniff said...

Wow, lots of good suggestions. mmkramp, I'll email you this morning. Intergalactic, thanks for the Cam-Lok hint - I had been looking for a good single pole connector. I've got some friends in the theater business - they may be able to hook me up with a good source.

Intergalactic, I came to the same conclusion about flooded. I'm going AGM, though (Concorde AGM-1280T) - with regulators to avoid over-charging. I've gone with the Manzanita Micro charger (should be showing up soon, hopefully, since the batteries show up next week).

I'll explore the 2WD option some more. In addition to reducing mechanical inefficiencies, it would reduce weight and complexity...

Ross Cunniff said...

P.S. intergalactic, my email is my last name at sprynet (com, if you know what I mean). I'd love to chat some more via email. Specifically - how do I know if I have a "good" U-joint? Also, still looking for good info on battery thermal management... thanks!

intergalactic said...

you get my private e-mail?

Ross Cunniff said...

Yes, thanks - I was sick-as-a-dog all weekend so did not get a chance to reply.

mcqueen said...
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High Performance Lift Kits said...
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Ross Cunniff said...

I deleted a couple of what looked like spam comments totally unrelated to this blog. If you guys would like me to reinstate them you'll need to persuade me.