how to soften 3-4

[77 cruiser]

My 3-4 is a bit on the harsh side, & I'd like to soften it a bit before I break the OD carrier. I already had one that developed a crack. It has the TransGo kit now with the holes in the plate sized to their specs. Can I do something with the 3-4 accum?

 

[jakeshoe]

Jim,
If you are running the 3 clutch OD setup that firms up the shift by itself.
You could go back into the 3-4 accumulator and try it with the spring in the case and then the piston, instead of the GN setup. If you do that I would use a lighter spring.

Or you could start with a new seperator plate and not drill the 4th feed.

 

[77 cruiser]

Thanks Jake, I do have 3 frictions. I've tried the piston both ways & it didn't seem any different, didn't try any diff. springs yet. I'm not even sure what spring is in it for the accum.

 

[bison]

Thanks Jake, I do have 3 frictions. I've tried the piston both ways & it didn't seem any different, didn't try any diff. springs yet. I'm not even sure what spring is in it for the accum.

What size is the 4th feed hole? Id go back to the smaller hole size and go from there. I have the spring that CK uses on top of the piston and a .110 hole and the 3-4 isnt too harsh at all with 3 clutches in 4th. Your accumulator may be bottoming out too soon.

 

[77 cruiser]

I believe .110, kinda had it in the back of my mind the spring might be too soft, but I sure can't recall how strong it is.

 

[bison]

I believe .110, kinda had it in the back of my mind the spring might be too soft, but I sure can't recall how strong it is.

The accumulator spring in the vb might be affecting the shift also. What spring did you use there?

 

[77 cruiser]

The accumulator spring in the vb might be affecting the shift also. What spring did you use there?

The one that came in the TransGo kit. You are talking the accum. valve right.

 

[bison]

The one that came in the TransGo kit. You are talking the accum. valve right.

Yeah. Ive got CK's accum valve spring and 3-4 accum spring.

 

[77 cruiser]

I've got a CK kit so I could try that. Thanks!!

 

[bison]

I've got a CK kit so I could try that. Thanks!!

Be sure to back out the Transgo kit and use a new seperator plate with the proper hole sizes if going to the CK kit. You will need the stock vb springs you swapped out except the accumulator spring because the CK kit comes with a new one.

 

[jakeshoe]

The CK kit comes with a new plate, 3-4 acuum spring, and accum valve spring. Just install it as per the instructions and it will fix the harsh 3-4.

I'm surprised flipping the 3-4 accum piston and spring in the case didn't make it significantly softer.

 

[Ttype6]

The accumulator spring in the vb might be affecting the shift also.

This is what I've fonud to be the most likely cause of a harsh 3-4 shift. Many kits have you put a stronger spring in with the accumilator valve in the valve boby. I like to leave it stock or use the original line bias spring. I prefer to use stiffer springs behind the accumilator pistons to achieve a good feel. This is what bruce does at PTS. and I think his springs work the best.

 

[jakeshoe]

This is what I've fonud to be the most likely cause of a harsh 3-4 shift. Many kits have you put a stronger spring in with the accumilator valve in the valve boby. I like to leave it stock or use the original line bias spring. I prefer to use stiffer springs behind the accumilator pistons to achieve a good feel. This is what bruce does at PTS. and I think his springs work the best.

Bruce's kit causes a super harsh 3-4 IME. His spring is so strong on the 3-4 accumulator that is may as well be blocked.
Another thing I didn't like about his kit.

 

[blackplague]

Imho

I don't think the 3-4 apply hole in the spacer needs to be any bigger than .096, especially with 3 clutches.

 

[bison]

This is what I've fonud to be the most likely cause of a harsh 3-4 shift. Many kits have you put a stronger spring in with the accumilator valve in the valve boby. I like to leave it stock or use the original line bias spring. I prefer to use stiffer springs behind the accumilator pistons to achieve a good feel. This is what bruce does at PTS. and I think his springs work the best.

The stock spring is not adequate for a TR imo. It causes problems when the throttle position is approaching WOT and the line pressure has been upped. The accumulators dont work like they were designed to.

 

[bison]

I don't think the 3-4 apply hole in the spacer needs to be any bigger than .096, especially with 3 clutches.

For 500 ft lbs and under .096 is fine with the .500 boost valve and approximately 240 psi line. Most of the trans ive worked on in the last couple years had over 500 ft lbs so i went with a .110 hole and 3 or sometimes 4 clutches in 4th. I always use a spring on the accumulator to avoid cracking 4 carriers. Adding clutches to 4th is the most important part. 3 is usually no problem and the minimum imo. For 600 ft lbs and up 4 should be used if the trans will be shifted WOT into 4th. Running 3 or 4 with a blocker on the 4th accumulator will result in a cracked carrier eventually and a brutal jolt while shifting at all throttle angles if the line pressures are much over stock while using Alto reds. A billet carrier and ring gear would be required to delete the 4th accumulator in that instance.

 

[jakeshoe]

Most aren't going to do a 3-4 shift at WOT very often so if 4th is only used for the OD on the highway, there is no reason to have anything other than a clean crisp shift to 4th which is easy to accomplish using the stock GN 3-4 accum setup and 3 clutch setup and near stock orificing.

If it is going to be forced to do WOT 3-4 shifts under load with any real power then the billet stuff should be a part of the build and the shift calibration will change.

 

[77 cruiser]

The PT shifts are hard as well as the WOT shifts. The WOT shifts don't get done very often. I'll get under it when it cools down up here, we have some heat going on now, so I've just been hanging in the pool.

 

[77 cruiser]

On the other hand I should just put in the CQ vb & CK shift kit & GN gov. & be done with it but I just gotta play a bit.:biggrin:

 

[77 cruiser]

Here's what I'm gonna do.

Resize the 4th cl. feed to .085 roughly.
Slightly softer spring in the accum. valve.
The 4th accum. piston has a fairly soft spring on it now.

Should know tomorrow.