Downshifting TH400
04-08-2005, 10:24 PM
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Downshifting TH400 Haven't got to play with my trans yet. I was just wondering if downshifting on the fly, during a highway roll for instance, was too much for a TH400 to handle? Just didn't want to get the ole ricer fly by if I was in third. Also, don't want to destroy my new trans though. 
04-08-2005, 11:27 PM
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With a TH400 RMVB, you will not be on the highway that much. 
At 55, my RPM's are 3K. And you will be out of 1st and 2nd so quick. Even from a 30 mph roll you will not need to downshift. you will be in 3rd 99% of the time. Just mash it and go 
At 55, my RPM's are 3K. And you will be out of 1st and 2nd so quick. Even from a 30 mph roll you will not need to downshift. you will be in 3rd 99% of the time. Just mash it and go
04-10-2005, 10:21 PM
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I'm kinda curious about this as well. Is it alright to downshift while moving? Like if you roll up to a light and it goes green. Can you down shift back into first while rolling and not have to worry about anything?
Chris
Chris
04-11-2005, 09:52 AM
#6
I think he means that it isn't good to downshift into 2nd while you are at 60mph and let it do the braking for you. You know how you can downshift a manual transmission car and when you let out the clutch, it's effectively slowing the car down since you aren't on the gas. I think in a TH400/TH350 style trans, that's a bad thing.
04-11-2005, 10:08 AM
#7
On full manual valve bodies (RMVB) TH400 if you downshift, you run the risk of destroying your transmission if you downshift without coming to a complete stop! On a regular TH400, that still has the automatic properties, you can downshift at will. Which TH400 are you guys talking about? RMVB are intended for drag race use only!
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04-11-2005, 07:26 PM
#8
So you cant downshift the reverse manual t-400 at all? Not even if the rpms are low? Lets say your going cruising 50mph in 3rd gear, and want to drop it in second, you have to stop the car completely? I will be doing a t-400 conversion in my daily driver, and I didn;t mind the idea of switching the gears all the time manually, but not being able to downshift at all doesn't sound ok for a daily driver.
Can someone explain me to me how the t-400 with the auto propertys works? If I can downshift that one, I might as well get it. It probably costs more, right?
Can someone explain me to me how the t-400 with the auto propertys works? If I can downshift that one, I might as well get it. It probably costs more, right?
04-11-2005, 08:59 PM
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So it is alright to downshift if you are going to be giving it gas right after you down shift? Its not alright to down shift to slow down like you can do with a manul. Is that correct or am I still not getting it?
Chris
Chris
04-11-2005, 09:53 PM
#11
On my TH-400, Reverse Manual, you have to be going less than 20 mph to down shift to any gear. It is for drag race only. I don't know about a regular TH-400. Since it original (I think) came out of a truck, I don't see why on a normal 400 you could down or up shift it.
David
David
04-12-2005, 09:21 AM
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Go with a manual/auto or forward manual. This retains the intermediate band and rear band apply in 1st and is better suited for any street driving.
I am running a Forward Manual VB I built myself.
Steve
I am running a Forward Manual VB I built myself.
Steve
04-12-2005, 10:08 AM
#13
Correct! If you choose to run a TH400 with a transbrake, you can not downshift, especially for slowing down! The TH400 was used in trucks mainly, but some 400 CID cars got them as well. The OE setup TH400 operate just like any auto ... you can upshift and downshift at will, so long as your engine and converter can handle it (rpms). If you want to manually shift it, then get a (forward) manual valve body like S_J_H has. The reverse manual valve body is intended for drag racing only, as it is designed to lock reverse and 1st gear together for the transbrake. The standard TH400 will cost less than a RVMB with a Transbrake.
04-12-2005, 01:21 PM
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The disadvantage of the forward manual compared to a reverse manual is ET is slightly increased due to applying the bands and possibly band/clutch timing issues.
You see most RVMB have you remove the forward band and also do not apply the rear band in 1st gear. This is great for the strip but not so great for the street.
Seems everybody runs right out and buys a RMVB even for street use. Not the best way to run a th400 on the street IMHO.
here's what happens when you over spin the direct drum-
https://ls1tech.com/forums/automatic-transmission/197289-when-th400-s-blow-up-pic.html#post1590170
Steve
You see most RVMB have you remove the forward band and also do not apply the rear band in 1st gear. This is great for the strip but not so great for the street.
Seems everybody runs right out and buys a RMVB even for street use. Not the best way to run a th400 on the street IMHO.
here's what happens when you over spin the direct drum-
https://ls1tech.com/forums/automatic-transmission/197289-when-th400-s-blow-up-pic.html#post1590170
Steve
04-12-2005, 01:33 PM
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oops,You asked about auto/manual vs forward manual
Not sure, everybody does things differently with the VB's.
There are many mods that can be made to a th400 that effects the shifts.
One nice thing about any manual setup is you can start your burnouts in high gear.
Auto/manual is nice if you don't like shifting. But you need to mess with the govenor weights,modulator setting and hookup the detent switch.
Once it is dialed in the TH400 has real nice auto function.
Steve
Not sure, everybody does things differently with the VB's.
There are many mods that can be made to a th400 that effects the shifts.
One nice thing about any manual setup is you can start your burnouts in high gear.
Auto/manual is nice if you don't like shifting. But you need to mess with the govenor weights,modulator setting and hookup the detent switch.
Once it is dialed in the TH400 has real nice auto function.
Steve
04-12-2005, 02:14 PM
#17
How difficult is it to dial in the t-400? Do you need to open up the trans, or do you pop the cars hood, or crawl under the car to modify the govenor weights,modulator settings? I like the idea of it having the auto option, even though I will mostly be switching the gears manualy.
04-12-2005, 02:25 PM
#18
hmm. Completly different car, but my friends 396 Chevelle has a TH400 and he randomly downshifts(manually) from 3rd to 2nd or 3rd to 1st when racing on the highway or streets. I've never had a problem making the shift. They can't be as weak at the 4l60e. lol!
04-12-2005, 06:12 PM
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How difficult is it to dial in the t-400? Do you need to open up the trans, or do you pop the cars hood, or crawl under the car to modify the govenor weights,modulator settings? I like the idea of it having the auto option, even though I will mostly be switching the gears manualy.
And you NEED a 12 volt switch on your T.B. to activate the detent solenoid in the trans.
Steve
04-12-2005, 07:37 PM
#20
This is also what might happen if you don't drive a rmvb th400 properly.
I have one in a nova behind a 438 big block. I can go say 110 and put it in first and it'll idle.
Now why is that not good? First off doing this with no front band over runs the direct drum, thats why the one in the picture isn't there, the drum is gone.
Another thing that happens is the drum over runs so fast it slings oil out of the intermediate sprag and this can burn it up due to lack of lube. I've seen that happen once.
You can downshift for those ricer fly bys.
I was going 40 mph once and a girlfriend of mine was in a saturn coming up on me going 80. About a car length away I dropped down from third to first just to pop the rpm up to around 7500, then I hit second and third. She never passed me.
If you drive like this you must really know your car well. I have no rev limiter, that just means you have to know what your rpm is going to do. Sometimes I hit first only for a split second then pull down to second gear.
If I had worse traction doing this could be a real problem.
I have one in a nova behind a 438 big block. I can go say 110 and put it in first and it'll idle.
Now why is that not good? First off doing this with no front band over runs the direct drum, thats why the one in the picture isn't there, the drum is gone.
Another thing that happens is the drum over runs so fast it slings oil out of the intermediate sprag and this can burn it up due to lack of lube. I've seen that happen once.
You can downshift for those ricer fly bys.
I was going 40 mph once and a girlfriend of mine was in a saturn coming up on me going 80. About a car length away I dropped down from third to first just to pop the rpm up to around 7500, then I hit second and third. She never passed me.
If you drive like this you must really know your car well. I have no rev limiter, that just means you have to know what your rpm is going to do. Sometimes I hit first only for a split second then pull down to second gear.
If I had worse traction doing this could be a real problem.