Downshifting

[Darwood]

Robbie,

Really no bands, it's a clutch? I am having a hard time visualizing this. Do you know of a schematic or can you describe how the tranny is built. I thought all automatics used bands to control the planetary gears.

Also is this both for the 442 and 343 trannies?

 

[cary]

Bands were in the old transmissions and were a band form of a clutch with material on the inside of the band clamping on a round surface. Modern Transmissions use flat plate wet clutches that use pressure on disks, just like a normal clutch. I believe the mondern style is 1) more compact, 2) can handle more power, and 3) allows for more clutch material. Here is a link for how they work:

http://www.edmunds.com/ownership/techcenter/articles/43836/article.html

Cary

 

[tabraha]

I agree with Cary's evaluation of the situation. Everyone has got to concede the fact that gear changes during acceleration are harder on the tranny than just "engine braking" holding a gear downhill. Let's assume that during gear changes deceleration creates no more wear than acceleration. Well, rowing through the gears when accelerating is normal then correct? Now let's assume an average of 300,000 miles for the life of a tranny under these "normal" conditions. In this scenario, even if changing gears while decelerating creates no more strain than changing gears while accelerating normally, your life expectancy could take a significant hit because you could have as many as twice the shifts under load with this approach. I engine brake but have no use for downshifting daily or even weekly. The only time I go out of D is when I do not want shifting to occur in offroad situations and engine braking every once in a while.

 

[Darwood]

Thank you Cary for the information, I was a little behind the times.

 

[Photoman]

FWIW, I routinely downshift the trans when slowing and have never had a problem other than it popping out of Park from the weight in steep situations. Here is an overall of the A343F trans.

Bill

 

[Extreme_Trans]

Hi guys it's Rodney here from Wholesale Automatic Transmissions in Australia. I received an E-mail today asking me to join in on this topic as I specialize in all Toyota Land Cruiser and Nissan Patrol transmissions. I have read all your posts and they have been interesting reading. I can see that no one is completely confident about this and to tell you the truth neither am I but I can tell you about my observations and personal habits. I myself own a 1994 80 series with a A442F transmission that has now done 280,000Km and has been used mostly for towing my 3 ton race trailer. I often down change manually and have even been forced on a few occasions to down change at hi Rpm to aid in pulling the trailer up in emergency situations. I also down change from 4th to 3rd on a daily basis and service the transmission regularly, I have never seen any signs of ware what so ever! I have also never rebuilt a Land Cruiser transmission and found that manually down changing was evident or the cause of the rebuild and I have built and or modified well over 200 hundred of these transmissions. In saying that I can clarify a few things as we go here. 1st, The heat generated within the convertor during down changing is very marginal in comparison to up changing under load not to mention heavy weight towing that generates an incredible amount of heat while the lock up in the convertor is not on. 2nd Obvious signs of Manuel down changing and transmission failure due to this can be found on a daily basis in transmissions like the Turbo 350, 400 and 4L80E because of the very thin second gear braking band that has to bring a large heavy direct drum to a complete stop. I have also seen possible signs of this in many transmissions that run a band as second gear, this ware how ever can also be dismissed because of other possible contributing factors. 3rd' Very long down hill decents while holding the transmission in a lower gear even while pulling up a heavy weight such as a caravan will in no shape or form cause any ware within the transmission, even the heat generated in this circumstance by the convertor is moderate. 4th, The A440, A442F, A343F and A750 transmissions are extremely well built and lend themselves to Manuel down shifting although if any were going to ware I would think that the A343F would be first on the list as being the Only Landcruiser transmission to have ever designed using a band. 5th, It would be nieve of me to think that Manuel down changing will cause no extra ware as it must in some way because any down change under load causes the wet multi clutch systems that they have to slip that tiny bit more while they try to take up the extra load. I do how ever believe this to be minimal for the shear fact that I have never seen any signs of this during the rebuilding of the Land Cruiser transmissions.

Please forgive my long answer but I have never found a short answer for any transmission question. For anybody that is interested I have many photos and right up's about the A440F, A442F and hopefully by the end of this week and the A750F 5 speed. I haven't done a photo shoot for the A343F as of yet. I will post the links but only by invitation from a moderator as they do endorse my companies products.

Regards: Rodney Hudson-Davies Wholesale Automatic Transmissions

 

[drexx]

28Feb2004 (UTC +8)

Thanks for the contribution Rodney! I really appreciate inputs like that.

 

[lowtideride]

hey,
i got a fj60 so any downshifting you kind of get lurched forward.. so i guess ill try to keep that to min. but if i were to see a red light up ahead...would it be better to slowly push in the brakes?, or wait a lil bit and kinda push it down harder and stop quicker... which one creates more heat?...light slow breaking, slightly harder breaking and a shorter stopping distance...it seems like having the breaks on longer it would create more heat...hmmm i dont know
-al

 

[Gumby]

[quote author=robbie link=board=2;threadid=12059;start=msg111007#msg111007 date=1077816658]

Yes what do you mean by unecessary wear? Remember these are not american tranny designed only to last 80 to 100 k (except the new alison), before it gives you greif. [/quote]

Off topic thread hijack-

Actually, have heard that the new Allison is having a lot of problems. Folks have blamed it on GM cost ceilings causing Allison to redesign to lesser specs. i have yet to hear of a auto trans living up to the torque wars going on in the US truck market.

Regardless of how you justify it, my opinion is gonna be that downshifting causes transmission clutch wear regardless of auto vs. manual. As long as brakes are cheaper than transmission changes, I'm gonna continue to be lazy.
I do occasionally manual shift, but only because the Toytoa transmission tendancy to not downshift properly. If I turn on to a side street, for instance, it does not always drop down to second and lugs along in 3rd.

 

[Gumby]

Rodney,

Why don't you post up those links? Worst case I'll move them over to the vendors secton, but only if folks complain. If they've got good tech, I'd like to see them.

Gumby - The power behind Junk's throne. (makes me feel like Dick Chaney )

 

[IdahoDoug]

Excellent input and post. Nice to hear about the durability of the manly 93/94 models. Most people recognize that these were the high point for the model run, of course. Todd - you might consider adjusting the kickdown cable on your truck. Oh, wait - do the 343s have that feature or is it electronic?.....

 

[Riley]

[quote author=Gumby link=board=2;threadid=12059;start=msg112181#msg112181 date=1077978391]
Rodney,

Why don't you post up those links? Worst case I'll move them over to the vendors secton, but only if folks complain. If they've got good tech, I'd like to see them.

Gumby - The power behind Junk's throne. (makes me feel like Dick Chaney )
[/quote]

Todd - That simply is the funniest joke I have heard this year.

Rodney - Great info, thank you, it's great to hear from someone who works on automatic transmissions. It's always been area that I haven't understood well.

Riley

 

[e9999]

Hot dang, I love it when you hear from folks who actually know what they are talking about...

E

 

[landtoy80]

I had a dream last night.
I was driving on the hwy and for some reason I down shifted into 2nd. The rpm's went way up and...
I woke up.
I don't know what damage down shifting does but its hard on my sleep time.

 

[Gumby]

For those who didn't notice, Rodney did post those pics and they are great.

In fairness to other vendors, it was moved to the vendors section, but check it out. There's lots of good tech about your tranny in there.

 

[SteveLCetc]

[quote author=IdahoDoug link=board=2;threadid=12059;start=msg112333#msg112333 date=1077998629]
Excellent input and post. Nice to hear about the durability of the manly 93/94 models. Most people recognize that these were the high point for the model run, of course. Todd - you might consider adjusting the kickdown cable on your truck. Oh, wait - do the 343s have that feature or is it electronic?.....
[/quote]

That's what I'd like to know... I was driving through some hilly country on the interstate in Cruise Control yesterday, and my '97 wouldn't upshift when it should have. Is there an adjustment for that? I just had it flushed out...

Thanks
Steve H

 

[PHAEDRUS]

Rodney,
good to see you over here form the 3FE list. I lurk there but spend my time here primarily. FWIW if anyone want to see what kind of stuff he does go to the 3fe forms in yahoo and parouse a rather lengthy discussion on the valve body kits rodney is producing. according to the users there it is a good product. now I am just waiting to have any tranny problems so I might call on this valuable resource.
Dave
oh yeah no affiliation yada yada yada