What are the do's and do not's for downshifting in a full manual auto trans, namely, a 4L80e. I just got it back and it is my first full manual auto. I can theoretically downshift it to first at 45mph, I don't think I should, but is it something that is a definate no-no? If I drop it from 2nd to 1st at 45mph it will put me at about 5k rpms and that realllllly feels absoluting insane as it screams up to 6500rpms and to **** into 2nd at a tick under 60mph about 1/2 a second later.

So, what are the rules? What is okay to do and what is not okay to do? Also, when I am slowing down at a stop sign there is a distinct knocking or clank as I downshift 3-2 and then 2-1. The 3-2 isn't that bad but the 2-1 makes my *** pucker a bit. I wouldn't call it a clanking as much as just a general 'thud' or 'knock', just a single, fairly loud noise as I downshift. What would cause this? Could it be torqing and hitting something underneath the car or could a trans mount be loose? Any ideas? Thanks

 

The real risk to a downshift on that unit is not to the trans but your engine.

 

I would think that the low roller and the intermediate sprag are taking a pretty good shock as well. I guess it depends on how fast you are going. It has been with my experience that any manual valve body the down shifts are very abusive. Some kits even tell you not to do this. I would contact your builder and ask him these questions as we do not know what kit he has used here. Vince

 

unnecessary abuse, dont do it.

 

what about a downshift for a planned or spur of the moment roll race? even with a TH400? I want to swap to a TH400 RMVB soon and thought i saw a thread on how downshifting the transmissions can blow them up?

 

I drive my MVB 4L80 EVERYWHERE. I rarely have to lock it up. And I just down shift from 3rd to 4th. Once at a stop sign I rachect down to 1st again. Simple and easy. No problems!

 

This was the reason I went back to full auto on a street driven 700r4. To me, they only seem appropriate for drag racing where you only upshift.
Downshifts always felt "abusive" - I did have the engine breaking option (i.e. the overruns were enaged all the time) - which probably made it worse.

I once accidently pushed it back to 1st gear on a 2-3 shift - revs went through the roof - I also missed the kick down feature.

 

x2 There has to be a way to downshift more safely in a mvb auto. I am just finshing my th400 rmvb swap as well and you can bet you *** I am going to find a way to downshift the trans if I pull up to a z06 on the highway.

 

with a full manule you cant downshift 2-3 unless you have some throttle applied while downshifting. With the use of a manule/auto you keep the front band which applies when you ds and keeps the high gear drum from overrunning

thats how a th400 is, dont know if its different on the 4l80

 

Just keep your R's below 2K-2.5K; TH400's are pretty solid

 

my first car was a honda accord ('90), i used to shift it all the time (w/ 127,xxx miles)....i still think my motor and trans are still orbiting mars.

Point is, be careful!

 

Well the 4L80e has been rebuild with some pretty stout parts. I am not positive on the exact part numbers the builder used, etc. but here is a rundown from the receipt I got for the work:

O/D Planet
Drum
Stage 3 Kit
Center Support
Rear ring gear
High performance rear and front bands
New bearing, washer and bushing kit
High performance kit
Transgo full manual valvebodies/ HDII kit

I am not sure what specifics fall under "stage 3 kit" or "high performance kit", but I know that the sprag was upgraded and the clutches were also upgraded.

So if I am cruising at around 30-35mpg in 2nd gear at 3k rpms and someone pulls beside me wanting to play around, I should not drop it to first? It drops to first and engine speed goes up to about 5k and holds stead until I shift at about 6400rpms. Same if I am on the HW and going 60ish or so in 3 or D, if someone pulls up next to me, I can safely (safety meaning engine speed is not redlining) drop it down to 2. This will put the engine speed again in the 4500-5000 rpm range and will pull straight through until I shift again.
Am I understanding correctly that this is not okay to do? How the hell are you supposed to race anyone that pulls up next to you if you cannot downshift your transmission? Is there anything that can be done to the trans that would make it safer to perform this? I am planning on getting an aftermarket shifter so I have better control of my downshifts, etc but I would really hope than a transmission with close to $5000 invested in a core, swap and build should be able to downshift to pull on someone challenging you. This is really disheartening.

I'd like to hear feedback from anyone with knowledge or experience, but especially the sponsors. Thanks a ton guys
Mitchell

 

Well, if it means anything i used to downshift my auto from 3-2 all the time...it broke at 11k miles. I dont know if its because i used to downshift it while doing full throttle burnouts? I would be sitting at the top of 2nd gear smoking the tires, then let off the gas a little and downshift it back to 1st and it would peg the rev limiter.

 

Ls2pontiac-
Was the auto that you used equipped with full-manual valve bodies or was it a regular automatic transmission? Mine has full manual valve bodies and will only upshift and downshift by manually moving the A4 stick up or down, it will not do it automatically.

 

I'm going to have to remember this. I'm also wondering about the downshifting on the highway thing as my next trans will be a rmvb 4L80E.

 

It doesn't sound abusive on the highway at all. It sounds and feels smooth. It is like, pulling up to a stop light and going 3-2 at 35mph it feels like sumthin jolts the tranny, then at 10-15mph the 2-1 ds does the same thing, but my TRaction Control comes on. What the ****.

 

The jolt you feel on the downshift is the intermediate overun band coming on. Same with the manual shift to low 1 you feel the low/reverse band or in the 60e case the low/reverse clutch comes on. Now on throttle it may be a bit rough on the low roller clutch to pull down to manual one but on the flip side decell I dont see anyway it could hurt anythng , The roller clutch actually becomes non functional since the low/reverse (clutches or band) effectivly take it out of the picture. Just like if you were in manual low and cruise up to a certain speed and nail it there would be no stress on the roller clutch. Never really understood the roll race way of letting the car shift to second then back to first manually other than it does feel good since it would seem that if you just stayed in first to the speed you were going to nail it at it would be much more effective IMO

 

Thanks for the post performabuilt, that explains the jolt in a much less scary way. I was positive a tranny mount was going out even though they are fairly new poly mounts.
Would you advise against a downshift to race someone who happens to pull up next you on the highway or just a normal road? Or should I be in the clear as long as I'm not doing it 4x a day and dropping it to bring engine speed to 5k (which I'm not, usually brings engine speed to about 4k). Thanks