D4 shifting - gears clash

You need to push the clutch lever forward to engage the brake. Are you doing that?What clevis are you referring too? If it's the one on the release lever above the deck that doesn't do anything but change the lever position. You shouldn't have to mess with the rod/clevis down in the clutch compartment.

Hi again tinytec,
as OM has said above, provided you push the clutch control lever forward it should engage the clutch brake. There is no adjutment procedure or length of linkages given in Serv. Lit. that I am aware of for the clutch or brake linkages.
I would suspect that a stack up of lost motion due to worn :- shafts, bushings, linkages, and thrust collar and flange is the most likely problem, I guess your clutch lever is hitting the floor plate or the firewall. There is a double sliding spring setup on the detent linkage to allow this linkage to adapt to various linkage lengths when the clutch is adjusted to take up any wear.
I guess, as a tempory fix, you have nothing to lose by lengthening the rod and seeing what happens, provided nothing else in the clutch linkage/compartment clashes, and the clutch continues to be engageable.
Hope this helps,cheers,
Eddie B.

OM: Yes, I push the clutch lever fully forward. The rod/clevis I'm referring to is on the left side in the clutch compartment.

Eddie: There is a lot of accumulated wear in the linkages. As you suspect, the clutch lever hits the floor plate in its full-forward position.

Another thought just came to mind: Is it possible the drive shaft sleeve coupler has slipped forward on the (splined?) shafts so it is now farther away from the friction brake disc? The coupler looks like a two-piece split coupler with bolts and locked nuts.

BTW, the clashing problem didn't exist before I adjusted the clutch.

Thanks again for your information.

tinytec (unstuck Fred)

I had a D25J that I bought that did the same thing when it was cold but when warm, most of the prob went away and shifting, while not exactly the way it should have been, was possible. After dumping some diesel in the clutch housing, then engaging and disengaging it for a few minutes while warm and running and then draining it fixed it.
About the only other suggestions I have is to tear into it, either replace badly worn parts or braze, redrill and ream 'em. Don't forget to replace the brass bushing in the top of the clutch housing with a new one, that's where a lot of slop usually is.

I had a D25J that I bought that did the same thing when it was cold but when warm, most of the prob went away and shifting, while not exactly the way it should have been, was possible. After dumping some diesel in the clutch housing, then engaging and disengaging it for a few minutes while warm and running and then draining it fixed it.
About the only other suggestions I have is to tear into it, either replace badly worn parts or braze, redrill and ream 'em. Don't forget to replace the brass bushing in the top of the clutch housing with a new one, that's where a lot of slop usually is.

After fiddling with these clutches for 40 years or so it has come to light that one of the biggest culprets in the performance of these clutches is the 7B5758 cams. When I was adjusting the D8 clutch everything was larger and more accessable to view and is exactly identical to the D4. It seems to me that the profile where the cam contacts the pressure plate must wear over time. This cam is what provides the snap that put pressure on the plate and also provides for the amount of release avaliable. I wonder if these cams are still available from Cat and what the cost would be. On the other hand it seems to me it would be possible to remove them and build them up with hardface rod and re profile them.

It's not just the cams....but a combination of wear on the links, pins, and cams that makes up the toggle mechanism or the lack of.

Eddie ("There is a double sliding spring setup on the detent linkage to allow this linkage to adapt to various linkage lengths when the clutch is adjusted to take up any wear.")

Your info. makes me wonder if this double sliding spring linkage has a problem. I will get back to the CAT on Tuesday, and with the help of all inofrmation given here, will look into the linkage more thoroughly.

Thanks again . . .
tinytec Fred

Reference from previous posts:

Eddie: ("There is a double sliding spring setup on the detent linkage to allow this linkage to adapt to various linkage lengths when the clutch is adjusted to take up any wear.")
tinytec: Your info. makes me wonder if this double sliding spring linkage has a problem. I will get back to the CAT on Tuesday, and with the help of all information given here, will look into the linkage more thoroughly.
===================================

I worked on the clutch linkage today and noticed there appears to be only one spring, not two, near the clevis.

I caused the gear clashing because I previously adjusted the clevis in the wrong direction. I had extended the clevis as far as possible without the threaded portion falling out of the clevis assembly. Today I reduced the clevis length - this eliminated the gear clashing by allowing the brake disc to stop the free-wheeling transmission shaft while shifting gears. When I mis-adjusted the clevis it prevented the brake friction surfaces from ever making contact with each other.

Now I'm wondering if there is a missing spring in the double sliding spring linkage. . .

tinytec