4R70W Delayed Engine Braking

[V8BoatBuilder]

Ok, here's a challenge for all our tranny gurus:

My 4R70W has great engine braking when in 1st gear, only after the truck has been moving for about 5 seconds. Before that, it's useless. For example:

If I start out going down a steep hill, it will roll fast and then slow down, without any driver input. Once it slows, I can let the truck idle down the hill without use of the brakes. But, for the first 5(ish) seconds, it will roll fast.

I want to fix this, because on rocks or other challenging off-road situations, it can be quite annoying.

How can I fix this, so I get 100% engine braking from a standstill??

 

[Glacier991]

ok what lever position? Manual first ? or ?

yeah I know, glad to be back as well.

 

[Glacier991]

Ok, I have been waiting on pins and needles for a respone that is obvious.... so...

The question you need to answer is WHY is my OD band slow to apply?

Half of the possibles are in the VB.... the others are in the servo.

In your case, you ought to be able to fix this with the tranny remaining in vehicle.

Nice to see you again Aaron.

 

[Willard]

Thought I'd throw this in here....it wouldn't be from the engine's delay before it idles down all the way, would it? I've noticed this same thing in other vehicles, including one of them being a manual transmission.

Btw....nice to see you again, Glacier. I'm sure you have no idea who I am, but I've read your diaries over and over again.

 

[Glacier991]

Thanks Devilboy, glad they have been worthy and of assistance. My legacy it seems. Happy you like them.

The engine speed, at idle, is enough to pump sufficient tranny fluid to engage what needs engaging (assuming the pump is ok) so the real issue here is not related to engine speed, but fluid routing and timing issues of band apply - in my opinion.

The Valve body has a regulator in it, and it maintains line pressure at a constant level, regardless of engine speed, and the idle speed is enough to reach regulated operating pressures - normally. Your point though, is a good one. So I ask....

Aaron, got a pressure gauge?

 

[V8BoatBuilder]

Fantastic response in less than 12 hours - amazing! Glad to see you back too, Glacier. I never really went away, just had to finish school and move to a new state, but now that I'm tinkering on the truck again, I'm spending quite a bit of time on the boards!

ok what lever position? Manual first ? or ?

The lever is in "1"

The question you need to answer is WHY is my OD band slow to apply?

So there is a cause for this, it's not normal!

...it wouldn't be from the engine's delay before it idles down all the way, would it?

The idle was between 800-1000rpm for a bit, I'd be standing still on the rocks before I observed the problem.

Aaron, got a pressure gauge?

Do I need a special trans pressure gauge? What psi range, where/how does it connect?

 

[Cobraguy]

When you accelerate in manual low, then let off the gas, does it hold low gear? Or does it go to "neutral", then apply the band?

 

[V8BoatBuilder]

When you accelerate in manual low, then let off the gas, does it hold low gear? Or does it go to "neutral", then apply the band?

Goes to neutral, then applies the band, after a few seconds.

 

[Cobraguy]

That is weird. Are you thinking maybe a servo problem? Or do you think it's an application delay of some sort? I guess I'd better get my flow chart out for manual low and see what we're missing here.

 

[V8BoatBuilder]

Bump... Don't wanna let this die when we were getting somewhere!