downshift clunk?

[liv4gnz]

seems like when i start slowing down to s stop sign when it downshifts into first it kind of clunks down into gear, the engine mounts and trans mounts are new, and the u joints arent bad, im thinking there is slop somewhere, the driveshaft has some play if its on the lift in nuetral if i try to turn it, is that normal? like maybe moves an inch clockwise or counter clockwise if i turn it? im gonna pull the diff cover off this weekend to make sure theres not a broken tooth somewhere either, the tv cable is also adjusted the way it should, i dont know if its something interal or not, any ideas?

 

[highboostgn]

Same thing with mine. Subscribed

 

[larrym]

what kind of 2nd gear servo on the trans and is there a cushion spring on it

 

[liv4gnz]

dont know ill have to ask dave how he built it lol but is it normal with or without it?

 

[larrym]

when i had no cushion spring on my super servo it would clunk on the down shift it was worse in D than OD

 

[Buick Mark]

Could be backlash between your ring and pinion gears

 

[Boostdeznuts]

Even when the car shift into second gear we saw 3.5 knock

 

[RmvBfrFlght]

If the 200-4R is like the 700R4 in it's operation, it is likely the 3-2 down shift that is clunking. The issue is caused by a very short period of time where the transmission is in 3rd & 2nd at the same time, causing it to lockup (just for an instant).

This causes the backwards back-lash in the drive train to be taken up, which causes the clunk. It usually makes a sound like the drive-shaft going 'ping', along with a clunk if the ring & pinion also hit.

It is a timing issue where the 3/4 clutch pack isn't being released before the 2/4 band is being applied.

One thing you can do is to slip the trans into neutral before the downshift occurs. Then slide it back into D or OD once below 10 MPH or so.

RemoveBeforeFlight

 

[liv4gnz]

so it would be considered normal with out any damage to the trans?

 

[RmvBfrFlght]

so it would be considered normal with out any damage to the trans?

No & no.

RemoveBeforeFlight

 

[liv4gnz]

soo its bad not to have a cushion spring installed?

is that what it sounds like it is?

does it cause damage to the transmission without the cushion spring?

what is the advantage of the trans builder to remove the spring?

 

[RmvBfrFlght]

Doing some research on the downshift clunk, I found a TCI install for their servo. They claim that without the cushion spring there will be a 2-1 clunk. Here is the link:

news.compperformance.com/Instructions/386005.pdf

On my car I data logged and marked the log at the time of the clunk. The transmission was in 3rd just prior to the downshift clunk. So I figured it was a 3-2 downshift. Maybe the trans does a 3-2 followed by a quick 2-1. I do know that there is a clunk plus a driveshaft 'ping.' It doesn't sound good. This is also a built transmission with a large servo.

With the weather getting better I am going to look into the clunking more. I would like to correct it.

RemoveBeforeFlight

 

[larrym]

I could see the cushion spring affect apply timing the pros could say more but I think the 2nd gear servo is also part of the 3rd gear shift works like the 1-2 accumulator, with out it there is nothing to slow down the servo pin accept for the band.
The only reason I brought it up is I had a 3-2 down shift clunk and removing the spacer and installing the factory cushion spring cleared it up.
Talk to your builder he should have an answer for you. Check the easy stuff first U joints mounts. The tranny mount can look good but there is not much to a stock one.

 

[77 cruiser]

3-2 clunk but never a 2-1 Can anybody ever feel the 2-1 down shift? When it down shifts coasting down it's the same as going to neutral, when the band releases it is over running the roller clutch with no engine braking.

 

[Chuck Leeper]

Data log it, and see where the rpm is when this happens. If the rpm is hanging a bit, it can cause added "clunk".
Excessive back lash will also do it.
A broken tooth will most likely result in noise most all the time. Most likely, it will be only a matter for time B4 it takes the entire r&p out.
NE worn out rear suspension bushings?

 

[RmvBfrFlght]

3-2 clunk but never a 2-1 Can anybody ever feel the 2-1 down shift? When it down shifts coasting down it's the same as going to neutral, when the band releases it is over running the roller clutch with no engine braking.

This is my thought too. The 2-1 shift can hardly if at all be felt. It has to be the 3-2 shift that is causing the clunk. It is all a timing issue between the 2/4 band being applied and the 3/4 clutch pack releasing.

I have a data log of it, but don't know which one it is

Shifting into neutral prior to the 3-2 shift eliminates the clunk/ping, but the trans is still going to be locking up for an instant. It just may be time to pull the servo stack out and see what is in there...

RemoveBeforeFlight

 

[Michael30815]

I have a hard clunk as well on my tranny that I had rebuilt with billet servo. Only from 3rd to 2nd gear. I wonder could this over time cause U-joints to fell. My U Joints felled after I put about 700 mines on rebuilt tranny. They were stock from factory, just wonder if the hard downshift had any thing to do with it?

Sent from my iPhone using Turbo Buick

 

[TexasT]

I have a hard clunk as well on my tranny that I had rebuilt with billet servo. Only from 3rd to 2nd gear. I wonder could this over time cause U-joints to fell. My U Joints felled after I put about 700 mines on rebuilt tranny. They were stock from factory, just wonder if the hard downshift had any thing to do with it?

Sent from my iPhone using Turbo Buick

Pretty well documented that the superior servo eliminates the spring per their instructions thereby causing this down shift "clunk". You need the spring to absorb the "clunk".
Sonnax, ck, and stock all retain a spring. It is needed.

 

[liv4gnz]

the small clunk is actually normal its the timing from when the 2cd gear band releases than goes right into first. but i think i just have slop in my rear lol

 

[longball]

[quote=" i think i just have slop in my rear/quote]

Damn man, I told you not to bend over in front of (insert name here).................