Yes and no. The only suitable unit that I am aware of - assuming that you still have the final drive reduction and need an additional stage before that - is the ev-TorqueBox. It is stronger than most conversions need (because it was intended for trucks), and it is a limited-production product, so it seems wildly expensive to me for what you get... but it works. Apparently there are various ratios available, but I doubt that they are as high as 3:1 or 4:1.
Yes, the question is from someone who (at least tentatively) is planning on using the front and rear final drives of a production 4WD vehicle, and that's what I meant by this:
The reduction of a typical final drive alone is enough if you are using a motor which only goes to perhaps 3,000 rpm. If you want to use a broader speed range of a higher-speed motor, more reduction is required - that's what an additional gearbox would be for.
These are great answers people.. Thanks so much.
So sorry, I forgot to mention - it's for a 4wd using a pair of DC forklift motors. I'm trying to avoid cost and complexity.
While it doesn't really matter whether or not it is rear wheel drive, it does matter if the final drive is included in a transaxle (front wheel drive, or rear-engine rear wheel drive, or even some front engine rear wheel drive if they have a rear transaxle), or if there is a separate transmission and final drive.
The idea of using a motor through a fixed reduction ratio (whether it is just one reduction stage in the final drive, or two stages) is certainly workable... especially with high voltage systems as used in modern EVs. With relatively low-voltage systems peak power is only available over a narrow range of speed; with a lot of motor power for the vehicle weight (like Duncan's Device) that's okay, but it may or may not be acceptable for other motor-vehicle combinations. The advantage of keeping the transfer case (and thus using only one motor for both axles) is having high (1:1) and low (reduction from less than 2:1 to as extreme as 4:1, depending on the transfer case) ratios for normal driving and low-speed situations.
DrGee, when you skip to a new thread, on the same build, you need to bring the rest of us up to speed on the basic info from your original thread. Better yet, try to stick to one thread to avoid the confusion. Most of us(except maybe Brian?) have a life outside of this forum and can't read and parse every post that's ever been written.
LOLTo be fair, the question in this thread is a distinct and specific topic, which would be reasonable without the whole context - all it needed to include was the use of the original final drive unit (diff).
Thanks for your reply Brian!LOL![]()
But seriously, the 4WD scenario is of particular interest to me, I had responded to the main thread, and it was recent, so I happened to remember it.
To be fair, the question in this thread is a distinct and specific topic, which would be reasonable without the whole context - all it needed to include was the use of the original final drive unit (diff).
There is an advantage to keeping a thread to a more narrow topic - it is less likely to get sidetracked and become a massive pile of discussion in which no one can later find anything. A link to the other thread "for anyone wanting more background" would work fine for me.
This approach has been used for FWD, but in this case DrGee is talking about a 4WD vehicle which comes with similar final drive units at front and rear.
The input shaft (propeller shaft) to the rear of a front-engine vehicle is obviously 90 degrees to the axle, and in a typical 4WD system with a longitudinal engine the same is true of the front (the front propeller shaft is running forward from the transfer case which is in the middle of the vehicle).
Front axle parts are similar to rear axle parts from a vehicle with independent rear suspension, although outer joints may be a different type of CV (for greater angular capability at the front), and shaft lengths are usually very different left to right in the front of a 4WD system (because the final drive sits to one side of the engine).
Okay Mizlplix,
This assumes a specific size of motor, a specific motor speed range, and some final drive gearing. Obviously with a larger motor, a single-speed transmission works for a heavier car, and with a smaller motor, the single-speed transmission would only work for a lighter car. What is the assumed motor size/power?
I assume that we're still talking about a 2011 (model year) Jeep Grand Cherokee WK2. If Wikipedia's list is correct, this has a Mercedes 5-speed or Chrysler 5-speed (depending on engine), not the later Chrysler 6-speed. The number of gears isn't important, but different transmissions may come with different transfer cases, which may mount differently. All should detach reasonably easily from the transmission.
Fundamentally, it should work.
I've decided to use my 2005 WK Grand Cherokee. It has nearly 200,000 miles on it, but still runs flawlessly. (Couldn't justify searching for a 2011 with a blown engine, when I've already got my '05 which I know so well).
