4th gear (o/d) weakest link?
 

I took my truck in for a tranny service recently.. fluid and clean filter. I was advised to drive my truck with O/D off, especially around town and upto 50-55mph on the highway if it is hilly.

The reason for this he said is that the 4th gear is the weakest link in the tranny. Also.. he said my fluid had "an extremely faint burnt odor" to it, and that if it was a domestic vehicle they would have condemned it for ANY odor of that sort.

I have been told not to use O/D much in the past, but that was with a Ford. It just uses so much more gas not using 4th gear that it is rediculous.

The truck shifts beautifully and they agreed, not a single glitch on either test drive they did. It's an A340H/160k mi.

Just looking for some opinions, thanks!

Not really a weak link per se....but rather the tranny is not geared as good as it should be. What is happening is that for in town cruising...your tranny is shifting back and forth from 4th to OD. This really heats up the engine and tranny, and couild potentially affect their service life.

My bro in law just had to rebuild his auto tranny since it was slipping, etc. The mech said the exact same thing.

I would do it...just to extend its life...but I would not say that you HAVE to.

I've heard that recommendation and personally I think it's rediculous. If you keep your tranny serviced and always maintain correct fluid level you shouldn't have any problems on a stock vehicle. I've heard of runners and tacos going 300k with no tranny problems. If you've got bigger tires and no gear swap thats a different story. If you want to buy some insurance then buy a good tranny cooler.

So is it bad to leave it in O/D all the time?

I ask this because I have heard it saves gas....

It definately does that. I got about 120 miles to this last tank w/o overdrive :barf:

I always service it on schedule. What do you think is causing the burnt odor? I could hardly notice, it was nothing like the burnt I smelled on my old Ford before the tranny croaked.

I understand that a lot of shifting in and out ofgear will create heat, but I've never seen the AT oil temp light come on.. even keeping it in OD the whole way to Los Angeles and back in the summer.

I was also wondering, what is the max safe speed to shift in and out of O/D at? The manual only shows 4wd, 2nd gear, 1st gear max speeds. I've done it a 55 without letting off the throttle and it feels like ti shifts smoothly.

Trans fluid should be done every 15-25k.. period.. Did you physically smell it as burnt and did the color look brown? If not they dunno wtf they are doing.

I thought the fluid smelled ok, not exactly like brand new ATF, but not burnt. The color was still pink but not as bright. It had been about 25-30k since the last change.