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Author Topic: Downshifting going down hill  (Read 10496 times)

Offline GUITAR1989

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Downshifting going down hill
« on: May 25, 2011, 01:44:57 am »
Hey guys I was driving with my brother and he allways shifts down when hes going down hill so he doesnt need to ride his brakes. I was driving in my truck and noticed when I shift down from 3rd to 2nd it doesnt hold me back at all and 1st makes me go wayyyy to slow. He has a manual Tacoma and my trucks got a TH375 auto. Should it be holding me back or is that normal for our trucks when going from 3rd to 2nd to not slow me down at all?  
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Offline 1979C20

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Re: Downshifting going down hill
« Reply #1 on: May 25, 2011, 01:49:36 am »
Its because he has a manual. A manual is DIRECTLY connected to the engine via the clutch. Automatics use torque converters which are kind of a free float between the two. Thats why when you stop an automatic, it still idles because of the free floating between the torque converter and the transmission. But if you stop with a manual without pressing the clutch it will stall because it is directly connected. It binds the engine and stops it from turning so it stalls. If the tires were broken loose and the rpms were high, then it would run at a stop because theres no bind stopping the engine from turning. So, the torque converter takes a certain RPM in a certain direction to connect the engine and transmission. Hope that makes sense.
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Offline Irish_Alley

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Re: Downshifting going down hill
« Reply #2 on: May 25, 2011, 04:02:31 am »
I had a th350 that would drop if I down shifted from 3rd to 2nd. I love to downshift in Maryland well the eastern shore we don’t have hills so the only time I do is when someone rides my but lol it like slamming on the brakes with no brake lights they usually come really close, if it too close I give it a little gas to avoid the accident but I’m sure they have a wet seat
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Offline Blazin

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Re: Downshifting going down hill
« Reply #3 on: May 25, 2011, 05:59:25 am »
I have downshifted my automatics for years. They do slow you down some. My 74 Malibu 454, with a built TH 350 would screech the tires when downshifted into first. my 95 Camaro with a stock trans and a V6 that I have now will chrip the tires as well when dropped into first while moving at lower speeds.
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Offline Irish_Alley

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Re: Downshifting going down hill
« Reply #4 on: May 25, 2011, 08:19:34 am »
it also depends on backpressure. i know even on my sm465 before i cut the pipes off would almost do a nose dive when i downshifted but once i gut the pipes off it has little to no effect
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Offline VileZambonie

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Re: Downshifting going down hill
« Reply #5 on: May 25, 2011, 11:12:44 am »
You should absolutely have engine braking in 2nd gear with your TH375. Are you sure it's going into second?
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Offline GUITAR1989

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Re: Downshifting going down hill
« Reply #6 on: May 25, 2011, 11:50:02 am »
Yeah its shifting into 2nd. If I should be getting held back what could be the reason its not?
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Offline bigchevyc30

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Re: Downshifting going down hill
« Reply #7 on: May 25, 2011, 05:38:38 pm »
idk i have a TH400 and it doesnt have the 1st or 2nd gear it just has the complete gears to change the ratio for like pulling a big load up a hill. it has L1 and L2 so i cant down shift
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Offline 1979C20

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Re: Downshifting going down hill
« Reply #8 on: May 25, 2011, 06:13:53 pm »
Whats your rear end gear ratio? That has a say in the matter too.
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Offline GUITAR1989

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Re: Downshifting going down hill
« Reply #9 on: May 25, 2011, 07:47:07 pm »
the gearing is 3.73 in the rear.
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Offline VileZambonie

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Re: Downshifting going down hill
« Reply #10 on: May 25, 2011, 07:57:15 pm »
Quote from: bigchevyc30 on May 25, 2011, 05:38:38 pm
idk i have a TH400 and it doesnt have the 1st or 2nd gear it just has the complete gears to change the ratio for like pulling a big load up a hill. it has L1 and L2 so i cant down shift

What?  ???
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Offline screamin86

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Re: Downshifting going down hill
« Reply #11 on: May 25, 2011, 08:02:23 pm »
Quote from: VileZambonie on May 25, 2011, 07:57:15 pm
Quote from: bigchevyc30 on May 25, 2011, 05:38:38 pm
idk i have a TH400 and it doesnt have the 1st or 2nd gear it just has the complete gears to change the ratio for like pulling a big load up a hill. it has L1 and L2 so i cant down shift

What?  ???


I was wondering the same thing lmao!
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Offline rwhit57

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Re: Downshifting going down hill
« Reply #12 on: May 25, 2011, 08:08:04 pm »
Quote from: VileZambonie on May 25, 2011, 07:57:15 pm
Quote from: bigchevyc30 on May 25, 2011, 05:38:38 pm
idk i have a TH400 and it doesnt have the 1st or 2nd gear it just has the complete gears to change the ratio for like pulling a big load up a hill. it has L1 and L2 so i cant down shift

What?  ???

This has got to be good. LOL
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Offline 1979C20

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Re: Downshifting going down hill
« Reply #13 on: May 25, 2011, 08:29:21 pm »
Quote from: GUITAR1989 on May 25, 2011, 07:47:07 pm
the gearing is 3.73 in the rear.
3.73s are a higher gear then 4.11, so it will allow less engine breaking than an automatic with 4.11's. Unless its a STEEP hill, you may not notice any slowing. My truck slows down in high gear with the gas out.
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1979 SCLB C20 Q-jet 350 SM465 14b F.F. 4.10 G80
1989 GMC Suburban V2500 TBI350 TH400 4in lift 35's 14b SF

Offline GUITAR1989

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Re: Downshifting going down hill
« Reply #14 on: May 25, 2011, 11:10:21 pm »
Dang  :( Looks like my brakes are gonne be getting the wrath cause where I live Its hills everywhere...Big Hills
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