bloodvette80

sometimes i wonder if I'm damaging my transmission by having it in 2 rather than 3 while crusing in town. it not only sounds better at a little higher RPM, say 3000, but also puts you higher on the torque curve so you have the power there as soon as you hit the throttle. Also when doing a fishtail around a corner, I'll usually put it down to 1 so it won't shift in "mid-doughnuit". I don't really want to spin a bearing so i don't rev it higher than 4500 or MAYBe up to 5000 on a blue moon. Anyone ever blow a 350turbohydramatic playing like I do?

Corz

I used to drive like that.. but after pulling the tranny pan down and seeing clutch matter laying in the pan I decided to knock it off. This was on my TH400. I also ended up spinning a bearing in the 327. It stays in drive from now on :yesnod:

Tominator

I do it all the time sense my tranny rebuild, it's a lot funner. Got around 7000 miles on it and haven't hurt it yet. I go a lot higher in the shifts than you too.

I love passing a car on 2 lane road going double-nickle then punching it to the floor and shifting down to L2.

Tom454

I haven't rebuilt a lot of automatics, but I have seen damage from manual downshifting in some of them that I have rebuilt. When you downshift an automatic, the driveshaft applies torque backwards through the tranny to the engine. It sounds cool..... especially through sidepipes... but the tranny internals are *USUALLY*not designed to take the "reverse" torque and certain internal parts take a severe beating. The tranny is designed/programmed to shift to avoid this. The damage varies depending on the make & model of the tranny, but I have seen the damage primarily on Ford C6's and AOD's. Maybe one of our resident professional transmission rebuilders will chime in.

Tominator

So there is a difference between it downshifting automaticly as aposted to you doing it manually?

Corz

:yesnod:

burners

We drive our family tow vehicle just like you describe, we downshift to slow down and to give it more punch when you want to slide around a corner. We are currently on our third engine (the last two making about 330hp) yet the transmission has lasted approximately 300,000 miles. TH 350's can take a lot of use and abuse but I don't believe that manual shifting is abuse. You will always see clutch material in the bottom of the pan, that is normal.

bloodvette80

oh great thanks guys now I won't feel guilty until i spin a main bearing at about 8000 rpm first gear doing a U-turn to catch 2 chicks in a sunfire. :lol:

flood

I do it all the time in my daily driver. Has 230,000 miles on a little 4 banger with an auto-magic.

It helps with my weight shift thru corners to downshift into second then floor it...lol.. Haven't noticed anything bad yet. :cheers: If course is FWD and not a vette....but still.

Tominator

Interesting topic, many points of view. Well like Tom454 hopefully someone can chime in to explain it.

bloodvette80

Me and Tominator would both like to know. :withstupid:

Matt Gruber

i used to drive auto's like a stick when i was a kid. i would rev it up and throw it in gear.
The Auto shop kids would do this to drivers ed cars. If they had a lockout we would backup fast(50?) and shift into D. :crazy:
.
i think tom meant WOT downshifts are OK,
but closed throttle downshifts can be hard on it

383LPE

auto trannys designed to shift have manual valve bodies

Alwyn678

I never have had any problem :cheers:

arrio76

Shifting up and down through manual 1&2 ranges will not hurt your trans any more than normal power acceleration in Drive. First gear in Drive range only applies the low sprag and forward clutch. When 1 is selected the low/reverse clutches at the rear of the transmission also apply to assist in holding first gear. Second gear in Drive range applies the intermadiat clutches and forward clutch. When 2 is seclected the intermediate band also applies to help hold. The Intermediat band only comes on when 2 is selected and not used at all in the Drive range.
So selecting the 1&2 ranges give the transmission more holding power in those gears.
(edit) Also in both instances, range 1 and range 2, the overruning sprags are locked by the applies of the Band or the Low/Reverse clutches. This is why there is extreme engine breaking during deceleration. The sprags still are still holding, but are prevented from overrunning.



[Modified by arrio76, 11:31 PM 7/7/2003]

Tom454

I was rebuilding a Ford Cruisomatic Cast Iron Case transmission a long time ago (1965 T'Bird with a 390 BB), and being my first automatic transmission rebuild, I had questions. So I went to a local transmission shop (Jacko Transmission in Binghamton NY) and asked the owner about the damage I saw. Since my father-in-law did a lot of business with him
(construction company) he (Jacko) took the time to explain to me that this particular transmission is not designed to be downshifted manually, although you could certainly drive it that way. He showed me the parts that took the brunt of the downshifting, and how they were not designed to be "run backwards". I rebuilt several other transmissions since then, and found evidence of the same problem. Maybe the TH350's and 400's don't have this issue. But a generic statement that "it's ok" is (IMOP) uninformed. We can all guess... it will take an actual PROFESSIONAL rebuilder (not a book reader or engineer) to answer the question. I build engines professionally, and I do an occasional Muncie.... but I don't do automatics for money so I don't qualify. The issue I was pointing out was not necessarily with the spragues or bands... and not with upshifting... it was with internal thrust in a direction opposite to normal operation that causes parts to wear excessively on each other that normally would not.. this occurs when the driveshaft/differential "brakes" the engine.

Again... maybe the newer transmissions and the TH3450/400's don't have this problem... but the issue deserves to be addressed and answered by a professional rebuilder (not a replacer).... someone who does this work every day.... hands on. I enjoy reading books on tranny overhaul and service manuals, but that doesn't count. Any opinions rendered from that vantage point are speculation. The answer has to be different based on which transmission design we are talking about. Some of the "older" trannys definitely cannot handle manual shifting, or more specifically "engine braking".

A real pro will be able to tell me exactly (not speculate or guess) why the Cruisomatic couldn't handle engine braking and the TH400 can, if in fact, that is the case.
I have a couple of 5.0 Mustangs (AOD)... and I manually downshift as well (sometimes). So I'm curious as well.

If you abuse your wife and she doesn't leave you it doesn't mean she is happy. Same goes for the tranny. :)

bloodvette80

Well my Tranny has never complained or screamed out in pain. I'm going to get a big stick and find my wife. jk

427V8

Well first of all I have read in owners manuals to use low in hilly country to save your brakes going down steep hills, so it can't be that bad!

arrio76

I re-read the original post. For what he wants to do will not harm the trans. The 1&2 ranges were designed for just that. To prevent the upshifting to the next gear. It also has the benefit of engine breaking for brake relief on long hill decents.
Another matter that may be of concern is repeated manual downshifting. If the trans is in good shape it should not bother it. Though there will be associated driveline shock loads to the drivesaft and differential.
Of course there is the usual caveate (YMMV) as most TH350's are 20-30+ years old and some have not even been through thier first rebuild yet. An old trans may have weekened/worn parts, worn thrust washers and half deteriated clutch linings nfrom age and high mileage. But to do as Bloodvette80 wants to do, hold the gear from upshifting, it would not damage the trans.
Just so you know, I rebuild transmission for a living. I don't claim to know everything, but I am comfortable with the above statement.

Matt Gruber

arrio
What is your opinion on shift kits, set on the race setting, for bang shifts.
They say the clutches last longer, but i wonder if these "chirp" shifts overload other parts and lead to failure.
thanks :cheers: