D or 3 for Transmission life extension?
 

Hello everyone. I read somewhere on some website that driving short distances or around town or up to get the groceries it's best to drive in 3 than in D, to put less of a load on the transmission. is this true? I cant really notice very much of a difference between driving in the two, but im a beginning driver. but i do notice that in 3 it drives slower, needs a bit more gas to move more than while in D, but not sure. Only got 36k miles on my 96 svx, and i wanna try me darndest to keep the transmission alive and kicking. what should i do about driving in D or 3?

Yes around town and below approx 50 mph use 3 which is direct drive whereas D is overdrive for cruising. The SVX has high gearing as you must have observed when watching the tacho.

If you are in D around town or on a winding road the tranny will constantly hunt down and up from D to 3 causing udue gear and friction surface wear. Also the torque converter will be slipping more and creating extra heat. What is more in very dense slow stop go traffic it can be good idea to stay in 2 for the same reasons.

It is a good thing to do a little thinking for the tranny. Auto it may be but it has a limited brain ! You will find a lot of info. and discussion on this subject in posts here if you do a search.

I drive in D exclusively, and while the tranny is not in the best of shape, I highly doubt that driving around in 3 would've helped considering that mine is a 92 and there were a variety of dealer service related issues that contributed to its current condition.

KuoH

Kuoh,

Please give concrete reasons for your doubts.

There are experts on the net who have given this very good and sound advice based on engineering principals. These principals are easily understood and the advice given will stand up against argument. On the basis of my knowledge I am prepared to state that there can be no argument.

Well, aside from the fact that my tranny temps weren't any lower when I tried driving around in 3rd instead of D, and the fact that my tranny was quite neglected and used by family members in south Texas for over a year and is still running, plus the incorrectly installed filter since 30k and I'm now at 180k, I have no concrete evidence. I'm no engineer nor have I disassembled and evaluated the component wear of every part of my tranny, but from past experience with my SVX, if I should get another tranny, I still wouldn't waste my time.

The main issue with our trannies is KEEP IT COOL, and the difference between driving in 3 and D is minimal if any at all. Your efforts would be better spent installing one or more coolers and a temp gauge.

KuoH

Hi Trevor,

The USA tranny has four (4) forward speeds and then the torque converter locks-up in forth. It is really a five speed auto.:) At least I had a few Cryslers that caled them 5 speeds.

I have found that the least amount of heat is gererated when the TC is locked-up and the car is NOT driven hard.

I have found that driving hard in 3 or D makes no difference. The temp out of the tranny still hits 240F (166C) on 95F (35C) hot days while running up and down hills.

I think that accelerating around city block corners puts a lot of heat into the trans becasue the transfer clutch is slipping most of the time under higher loads. This due to the difference in the front and rear shaft speeds out of the trans. (AWD USA models)

I also think that a stoppage/blockage of fluid in the cooler or in the control valve will cause overheating. For this a temperature gauge is needed.

I also think the tranny pan is a better place to measure the fluid temperature. However, I have not done this yet.

I also think that if the tranny starts to act up it can be corrected before it goes to pieces provided it is driven until the problem is found. In particular this applies to RWD transfer valve not working, clogged filter and brake band adjustment.

John

On my 97 SVX I drive in 3rd around town (up to 50 mph). On highways I shift to 4th. When I come home from work each night and inch along in stop & go traffic on I-476, I leave it in 3rd.

I also do this with my '92 but not as much. The '92 definately has more low end power. I think Subaru changed the final drive ratio.

Larry I think that low end torque power change is all in the ECU. Put in the FWD fuse for the 92 and it will be slower.

Heat problem
 

Quite a few cars seem to go for a long time without tranny meltdown. If so, lucky for those guys. My tranny has been apart twice in twelve months, I am not in a hot climate, nor am I a hard driver. Not so lucky.

When my car was first fixed to have four forwards, I drove in D, the brake band went, followed by the clutches. This time, to be sure to be sure, I am using 3 for town driving, and have an extra cooler installed.

Trevor is right on first principles regards heat. These trannies tend to change up quick, attain and hold D. When asked for power, if the TCU does not select 3 or lower, the T/C is doing all the multiplying, and is creating lots of heat in the oil. This will have worst effect where the temp peaks are held for long periods, such as long hillclimbs, or continuous town driving. Excessive heat will "kill" the oil over time, and cook the friction material. People who flush and change their oil very often offset this, and using special hi-temp synthetic is also a help.

I also suspect when you run two coolers or an additional big one [mine is 19,000 lbs rated] the ATF may be overcooled as a result. This may explain why Kuoh's does not show additional heat using D, if he has an extra cooler. My car seems to be about 2 mpg more thirsty than when I had no extra cooler, and I am putting this down to the oil not being warmed up a lot, particularly as I use the AC most of the time. The AC fan is pulling air through the new cooler and the OE one all the time.

To answer RC's first question, a '96 car does not have the troublesome mesh in the cooler, which is attributed to hastening the demise of the earlier cars' transmissions. It is likely if you put in an additional "helper" cooler, you can drive in any gear you like without worry, assuming you don't drag race it everywhere.:)

Joe:D

Hi Joe,

I your case I would be very concerned about the valve body getting cleaned-up after all those little failed pieces of metal get in there.:(

I think mine trans has lasted this long because the radiator was changed from the original 92 after a crash.

You may be right. That is why a dinosaur like me likes the old cars. They were all mechanical. None of this microchip stuff to confuse us old timers.

Spare set
 

Yeah Commuter

I was at one stage thinking of sending a spare valve body to Level 10 to be upgraded, but it got stolen in the robbery. I might still have the valve set redone, not a bad idea.

Joe

' 92 with ONE tranny replacement
 

We live on a rather steep hill and drove the SVX for about 4.5 years and exactly 55,899 miles before the transmission went South... We used to use 3 for going down the hill in the am, shift to D when we hit the freeway and would normally shift back into 3 (if we remembered to do so) on the way back up in the evening, or whenever.

Always drove around in D: had the 1st tranny serviced every 15K miles (Anyone remember when they used to send you the Subaru Booklet every couple of months with the coupons in the back for really cheap service? Like $24.95 for a transmission service?) and there was no warning, no slippage, etc. One day it just wouldn't shift past 2nd gear. Called the closest dealer, he said "Bring'er in tomorrow!"

Took it to the dealership @ 9 am, they drove me home in a shuttle Impreza, called me @ 3 pm to say "She's done: when do you want us to pick you up?"

This was all before I ever heard of this site, but after the 2nd set of rear wheel bearings. I just thought we had screwed up the tranny driving it around in 3 up and down the hill each day!

:rolleyes: Duh!

I still think the replacement transmissions with the final serial upgrades are pretty reliable... But, then again, I have been a very lucky man!;)

Re: Heat problem
 

Nope, my unscientific testing was done when I had the old tube & fin coolers, which did not cool as well as even one parallel stacked cooler. But here in Kansas City, things are relatively flat, so maybe there isn't much to cause an increase in heat while in D. But no matter which gear I selected the temps were 190+ in city.

KuoH