No hold back on let off?!

[libertysyclone]

I have noticed the last few times I have driven my Sy that when I let off the Rpms go to idle and there is no sence of a "holding back" like when you downshift in a manual w/no throttle. It used to be just fine. I have to assume that its my TC right? I am going do check the TV and service the tranny soon (the snow is melting) so I figured that I'd fix whatever the problem maybe while I am in there.

 

[Daryl H]

Re: No hold back on let off?!

There has to be someone with more trans experience then me but....I think it is one of the clutches in the trans that is gone bad. I put 50k miles on my transmission since I got it with 60k and otherwise still works fine.

 

[MikeRenz]

Re: No hold back on let off?!

and here i thought OD had no engine braking

 

[George Blake]

Re: No hold back on let off?!

Overrun clutch hub gets grabbed and slows you down if you are in manual D.
If you are shifting from OD to D and feel nothing you've done one or more things.
Overrun clutch hub is damaged. Piston seals blown off the overrun piston, overrun clutches burnt, sprag is going out...not catching like it is supposed to. Once the outer race on the sprag gets worn out, it will allow the sprag to slip some before it catches.
It's not the converter.

 

[Daryl H]

Re: No hold back on let off?!

and here i thought OD had no engine braking

I thought I read on the list a long time ago that it IS suppose to do it in OD.

 

[George Blake]

Re: No hold back on let off?!

Overruns are what applies "engine braking" effect. They are not applied in OD. Mike is correct.

 

[cloneman315]

Re: No hold back on let off?!

is this why if u leve it in drive and slow down it clunks when it downshifts?But if u leave it in od it dosent

 

[gkrcr882]

Re: No hold back on let off?!

Yup, as the chart shows the overrun clutches are engaged in all gears except OD, hence the "clunk" and the slight jolt.

 

[cloneman315]

Re: No hold back on let off?!

thought so ,does it hurt anything if u let it do this ex driving around town in d ?

 

[gkrcr882]

Re: No hold back on let off?!

No it won't, it is actually reccomended that you use "D" whenever you don't need overdrive because the 1-2 clutches are engaged, which keeps them from exploding. Only use OD when you need it, like on the freeway.:2cents:

 

[George Blake]

Re: No hold back on let off?!

If you are in 3rd, you'll have 5 forwards, 2 overrun and 6-9 3-4's depending on how you stacked up the drum. If you let it shift into OD, the 2 overruns will disengage. This loses two clutches moving you forward. Also, when shifting into OD you lose some mechanical stability. Meaning in 3rd you have a direct 1:1 rotation. Trans is much stronger in this configuration but you rpms are limited. Let it shift into 4th, band grabs, rear sun gear stops moving and the 5 forwards are still holding but are being overrun by the OD planetary. This is hard on the rear planetary. This "grabbing" at high rpm by the band is why I like the 400/4L80e better for really hard use. :2cents:

 

[cloneman315]

Re: No hold back on let off?!

so george are u saying deal with the clunk its better for the trans>?Around town that is

 

[George Blake]

Re: No hold back on let off?!

It's mainly uncomfortable. Part of the clunk is the 2-4 band also when it applies during downshift. To cushion the clunk you can install the Corvette cushion spring. For some reason our factory "corvette build" omitted this spring. Part number 8681195.
2nd servo
You can see where it's at in the above pic.

GM PART # 8681195
CATEGORY: All
PACK QTY: 1 CORE CHARGE: $0.00
GM LIST: $6.06
OUR PRICE: $3.45
DESCRIPTION: SPRING

 

[cloneman315]

Re: No hold back on let off?!

so is it better for the trans to shif it into od just be4 u stop at a light etc or leave it in d and deal with the clunk or what?

 

[George Blake]

Re: No hold back on let off?!

I'd just leave it in OD. You still have the 2nd band application to contend with and you can't turn it off. That way the clunk was hardly noticeable. In D mine was just bad enough that it would kick in the ABS system which was a piece of crap anyway. Your best bet is to use the corvette cushion spring and leave it in OD unless you are racing. Your not stopping when your racing

 

[libertysyclone]

Re: No hold back on let off?!

Wow George thanks for all the info, I drove the Syclone from my grandfathers shop today to my house, and sure enough the overrun didnt work 1-D it does however "clunk" when I manually down shift. And still shifts HARD 1-2 but oh well guess its time to break down and get a 4l80e If anyone is interested in a core mine will be available this time next year