Transaxle Oil

[TomEV]

After reading this thread -
http://ecomodder.com/forum/showthrea...wners-128.html
I decided to try a different type of oil in my Citicar transaxle. Originally, this vehicle was supposed to use 90w gear lube.

When I bought the Citicar two years ago, the transaxle/differential was quite noisy and I only drove it a few miles before I drained the oil. The transaxle (single speed, direct drive, no ring/pinion gear, just straight cut gears) had a couple ounces of sludge inside that looked like really thick Testor's silver model paint. I refilled the axle with conventional 90w gear oil, but the sound didn't change much.

For those of you have not been in an electric car, the gearbox is one of the main producers of sound. With no engine, one hears different aspects of a vehicle! The gear sound in my Citicar was bothersome enough that I eventually took the transaxle apart to see if there was a problem, but didn't find any significant issues.

I refilled the axle with 75w/90 synthetic (Valvoline). This made the gear sound somewhat quieter, and less tinny. BTW the oil no longer has the metal flake look... The original discoloration may have been break-in wear.

I drove it using the 75w/90 for the past year. This week, I changed the oil to Pennzoil Synchromesh manual transmission oil. It is supposed to be about 80w, but flows much faster out of the bottle than did the 75w/90.

The gear sounds from the transaxle are somewhat different, and seem to be a bit quieter. Near the end of a 20 mile drive today, I was able to get to almost 37 MPH, about 1 MPH faster than normal even though the batteries were about 70% discharged at that point. The Citicar now appears to coast farther than it used to. But most of that is subjective, and may be wishful thinking. I keep watt hour/mile data on this car regularly, and should have some objective results in a few weeks.

[TomEV]

Some preliminary results -

5 mile drive - 1.16 kwh - 232 wh/mile

7 mile drive - 1.58 kwh - 226 wh/mile

9 mile drive - 2.01 kwh - 223 wh/mile

This fits well with previous charging experience in this car - shorter trips tend to be less efficient. The past long-term average for my Citicar has been about 250 wh/mile.

I measure electric use with a kill-a-watt meter.

Unfortunately, the longer trip mentioned in the previous post (20 miles) was recharged away from a meter, so no data for that segment.

But based on these representative trips, the wh/mile has improved by about 10%. The only change I've done to the Citicar for the past few months was the differential oil change earlier this week. More data in a few days...

[Ryland]

this gear oil is safe for all the bushings and bearings in the axle?

[TomEV]

The jury is out on that question. Since the Terrell differential (transaxle) is very lightly loaded in a Citicar, and has the gear types that are found in a regular transmission, my guess is that it is probably OK for this application.

There are quite a few people out there that use Pennzoil Synchromesh in transmissions of much higher powered vehicles which makes me believe that it should work fine.

Pennzoil Synchromesh and many other transmission oils are rated at GL-4 from what I can find out, which won't hold up in a regular high-powered car differential.

Since you have a more conventional type of differential in your Comutacar (Dana/Spicer), you might need the pressure abilities of regular differential lube (GL-5 rated) because of the ring/pinion gear set - but maybe not since the Comutacar doesn't have very much power or weight either.

[Johnny Mullet]

Synchromesh is equivalent to 30 Wt oil and has friction modifyers in it. If it is working well for you, use it! I will not use anything else in either of my manual transmissions in the Metros. The Synchromesh also stays cleaner longer. I drained the trans on my 98 Metro after 30K (suggested change interval) and I felt that I wasted some good oil since it came out so clean. I am now going to go 60K before trans oil changes.

[TomEV]

Today's number - 10 mile drive - 2.21 kwh - 221 wh/mile

So, how much did the experiment cost?

$8.00 for a bottle of Synchromesh oil, saving $0.001625 per mile (compared to 75w90) works out to 4,923 miles to pay off... If the Terrell holds up as well as a Metro transmission, I'm in good shape!

[Ryland]

I have an EV beater as well, my 1975 Citi car, was thinking of using this oil in it.

[Christ]

OT question - do those Commuta's have suspension?

[TomEV]

Both Citicars and Comutacars have leaf springs and tiny shocks fore and aft. They ride fairly rough - it is an exercise to avoid potholes while driving...

[Christ]

I forgot why I asked that... Thanks for the answer, though. I'm sure when I remember, it will come valuable to whatever strange idea I had last night.