I have been asking Marlon questions about changing gear ratios for my GEM. I have a 5 hp 2002 825 with 12" tires and a 10.35 transaxle. I am toying with the idea of going to a 6.0 ratio to improve my top speed and battery mileage. My flat land speed is 32 mph. I was wondering if any of you have done this and what is your experience. With the tires I have on the car the motor I think it is turning about 4100 rpm at 25 mph and that’s what GE rates it’s hp at. I had it running 38-40 mph at one time so the motor was turning well above that and no damage occurred. I think I want the motor turning 4100 rpm in the mid to upper 30’s mph. With the motor having maximum torque at zero and generating max. I live in an area that has no long or steep hills and being a two passenger car the motor should handle it. I am getting fantastic battery mileage but I love to tinker. Let me know your thoughts.
Do you have to remove the front battery box to pull the gear box out? thx.
no… it will take you about 5-6 hours …if you have done it before it will only take you 3-4 hours not that hard at all…well worth the money…i went from 26mph to 37-38mph on the gps with 12 inch tires…
Thanks. I noticed in the repair manual that you can take the front frame bolts out and loosen the steering coupler and tilt the front suspension down to get more clearance to lift the differential out. I was hoping I could just wiggle it out.
This vehicle was designed as a multipurpose vehicle and with the factory setup the motor reaches it’s 4100 rpm rating between 20 and 25 mph. Which is good if you are going to use it as a golf cart. When you get to 25 mph looking at the torque curve you start fighting the counter EMF generated by the over speed of the motor. So it seems that putting a 6 to 1 ratio differential moves that 4100 rpm up around 40 mph and allows the motor to use more of it’s low speed high torque curve to move the car at street speeds and you are not fighting the counter EMFs generated by the motor. The motor controller may do away with some of this effect with limiting the field current. Anyway for us that want to go faster the ratio makes as much sense as putting in a bigger motor if you are operating on flat lands. Plus you are not over revving the motor. My concern is whether the 5 hp motor has enough torque to pull the car comfortably at lower speeds on the highway and go up a small steep hill occasionally. I have a e2 so I’m thinking this will work for me but an e4 or e6 a bigger motor would be needed. I’m looking forward to putting a 6 to 1 differential in mine in the spring so I’d like to hear the pros and cons of such a change.
The differential is not hard at all to get out dont over think it or over work your self…call marlon he is the man when u need parts…he will send u all the stuff u need…its not hard…the motor is heavy so be ready…
When removing the motor, do not force the four power cable studs. If they are rusted, remove the cables from the other end at the controller. The insulators where these studs enter the motor are plastic and will crack if forced. These insulators are not available. If it is cold outside, try to remove the motor indoors because the plastic connector for the tachometer sensor may crack. Have a new rubber bumper for the transmission input shaft on hand before removing the motor.
Daniel
Daniel… “Have a new rubber bumper for the transmission input shaft on hand before removing the motor”.
do you have a pic of this piece or where it goes… i just want to make sure i did replace mine
GEM part number is 0313-00168. This goes between the motor and transmission. In the 1999-2004 factory parts list, this part is item #3 on page 2. This should be less than $10.
Daniel
Oh yes, I have several of those bumpers. They are very important. Equally so is to lubricate the splines with a light coat of moly grease so the bumper can do it’s job. Keep the suggestions going. I appreciate all of the input. Marlon has the best price! I bought a deep 24 mm socket to take the half shaft loose from the wheel end. On my 2002 825 it’s a 15/16. Both will work but the 15/16 is a better fit. I was using a big crescent wrench.
Here is a picture of the motor spline and the rubber bumper that is pressed inside. The flat side is pushed in with cup side facing out. Remember to lightly lube the splines on the output shaft with moly grease…
mine is a 2009 es… i dont remenber this part…would it have stayed in motor?? i need to get one ?? what happens if you dont replace it??
The bumper will stay in the motor end of the coupler. You have to pull it out with needle nose pliers. When the transmission input shaft is pushed into the motor coupler it severely compresses it and can’t be reused. If you don’t replace it and lube the splines with a thin coat of moly grease. (I always clean both splines with kerosene and dry) The joint will make a “bruck bruck” chicken noise.
hmmm i gurss i need to lookin into this …
I personally would let it go if the drive train is quiet. But if you start getting strange noises when you let off the accelerator…then you know what needs to be done.
No noise now but I will keep an eye on it thanks
“YOU WILL BE ABLE TO TRAVEL 2 MILES ON THE 6:1 RATIO BECAUSE YOU USED HALF THE BATTERY ENERGY AND CAPACITY”
Question: You are using half the motor RPM but are doubling the amps. How does this increase range?
You might gain in reduced parasitic losses from reduced motor RPM but I don’t think you would double your range.
The spline lube sold by Honda for the Goldwing motorcycle is supposed to be the best. The BMW motorcycle forums say to use the Honda spline lube. Spline wear is a problem on the GEM.
Daniel
[quote=OLD HOUSEBOATER;17622]“YOU WILL BE ABLE TO TRAVEL 2 MILES ON THE 6:1 RATIO BECAUSE YOU USED HALF THE BATTERY ENERGY AND CAPACITY”
Question: You are using half the motor RPM but are doubling the amps. How does this increase range?
You might gain in reduced parasitic losses from reduced motor RPM but I don’t think you would double your range.[/quote]
I installed the 6:1 gear set in my stock '09 7hp eS last winter. I purchased the gear set from Marlon and he was excellent to do business with. With no changes to the controller and 16" low profile tires, my top speed (according to GPS) is now about 42 mph. With the tires and gear change the indicated speed is exactly one-half GPS speed.
My range has dropped dramatically. Stock range was 20-21 miles. Range is now 10-12 miles. I’m running GEM Gel batteries.
I like cruising with local traffic at 35 mph but hate the limited range I now have. If I had it to do over I’d stick with the stock setup.
Of course your results may be different. I’m an old ICE hotrodder and know virtually nothing about how or why electric vehicles work. I’ve just stated the facts I’ve experienced regarding the change. I bought the eS new in December 2009.
Exactly - You can have speed or power. You can’t have both for the same amount of battery capacity. I added a 7th battery to my EZ (42) volts and gained a little bit of both. The secret is battery capacity. I went back to stock 36 volts. Am happy with 21 MPH.
[quote=Laslonimne;17685]I installed the 6:1 gear set in my stock '09 7hp eS last winter. I purchased the gear set from Marlon and he was excellent to do business with. With no changes to the controller and 16" low profile tires, my top speed (according to GPS) is now about 42 mph. With the tires and gear change the indicated speed is exactly one-half GPS speed.
My range has dropped dramatically. Stock range was 20-21 miles. Range is now 10-12 miles. I’m running GEM Gel batteries.
I like cruising with local traffic at 35 mph but hate the limited range I now have. If I had it to do over I’d stick with the stock setup.
Of course your results may be different. I’m an old ICE hotrodder and know virtually nothing about how or why electric vehicles work. I’ve just stated the facts I’ve experienced regarding the change. I bought the eS new in December 2009.[/quote]
Best of luck.