Gear hunting and major vibration in dash/wheel

[dogmagolf]

I just got the car back after replacing the B&M Shifter assembly with a stock OE 1970 slapstick and linkage. Prior to this, the car had a major issue in the rear which ended up being a bump stop issue, but it had made the vibrations and gear hunting less noticeable simply because it was a wreck to drive. Now that this is sorted out, the vibration and gear hunting is very noticeable (because it is the last thing to sort out I suppose) and I am curious what everyone's thoughts are.
So the gear hunting seems to spark the vibration issue in my opinion. The car cannot seem to decide between 2nd gear and 3rd gear. It shifts very smoothly into 3rd at about 32 mph (cannot confirm as we don't have the speedo fully sorted out, but that is about what we believe it to be currently). However, if I don't keep pushing it to 35+ MPH and just float along at 30-32, the car will shift back and forth between 2nd and 3rd, no matter how I play with the gas. Basically, I cannot hold 3rd unless I am closer to 35-38 MPH, and cannot hold 2nd unless I am around 28-30 MPH. My thought is an adjustment on the kick down pressure. (Note, this issue occurred prior to the new slap stick install, and feels no different with the new shifter.)
Next, is the vibration issue, which I feel is very much related to the gear hunting. When the car is in 2nd gear, very close to the shift points above, there is a major vibration in the front. Enough that the dash shakes enough to very visibly notice, as well as the steering wheel. Everything feels fine otherwise. The shaking is not present cruising in 2nd gear before the shift point (say 25 mph) with or without throttle, and in 3rd gear say 35+ Mph (throttle or no throttle). The shaking only occurs between those speeds when the trans is looking to shift, and only with the throttle on. with no throttle, there is no vibration.
The first thought was the wheels need balanced and I likely lost a weight at some point, causing the vibration to occur at a certain speed, however it only occurs with throttle, not just coasting at the same speed which makes me believe it is not a wheel balance issue (would think the speed would be the factor, not the throttle).
To me, it seems like it may be a trans issue of some sort, where the vibration is coming from the gear hunting and not being able to grab the correct gear, and wanting to kick down while at the same time shifting to 3rd.
Any thoughts or experience with this?
TIA
Jon .:R

 

[Ricks72Chlgr440]

I just got the car back after replacing the B&M Shifter assembly with a stock OE 1970 slapstick and linkage. Prior to this, the car had a major issue in the rear which ended up being a bump stop issue, but it had made the vibrations and gear hunting less noticeable simply because it was a wreck to drive. Now that this is sorted out, the vibration and gear hunting is very noticeable (because it is the last thing to sort out I suppose) and I am curious what everyone's thoughts are.
So the gear hunting seems to spark the vibration issue in my opinion. The car cannot seem to decide between 2nd gear and 3rd gear. It shifts very smoothly into 3rd at about 32 mph (cannot confirm as we don't have the speedo fully sorted out, but that is about what we believe it to be currently). However, if I don't keep pushing it to 35+ MPH and just float along at 30-32, the car will shift back and forth between 2nd and 3rd, no matter how I play with the gas. Basically, I cannot hold 3rd unless I am closer to 35-38 MPH, and cannot hold 2nd unless I am around 28-30 MPH. My thought is an adjustment on the kick down pressure. (Note, this issue occurred prior to the new slap stick install, and feels no different with the new shifter.)
Next, is the vibration issue, which I feel is very much related to the gear hunting. When the car is in 2nd gear, very close to the shift points above, there is a major vibration in the front. Enough that the dash shakes enough to very visibly notice, as well as the steering wheel. Everything feels fine otherwise. The shaking is not present cruising in 2nd gear before the shift point (say 25 mph) with or without throttle, and in 3rd gear say 35+ Mph (throttle or no throttle). The shaking only occurs between those speeds when the trans is looking to shift, and only with the throttle on. with no throttle, there is no vibration.
The first thought was the wheels need balanced and I likely lost a weight at some point, causing the vibration to occur at a certain speed, however it only occurs with throttle, not just coasting at the same speed which makes me believe it is not a wheel balance issue (would think the speed would be the factor, not the throttle).
To me, it seems like it may be a trans issue of some sort, where the vibration is coming from the gear hunting and not being able to grab the correct gear, and wanting to kick down while at the same time shifting to 3rd.
Any thoughts or experience with this?
TIA
Jon .:R

Wheels/balance has nothing to do with how the transmission is shifting. Sounds like the transmission is slipping. With the vibration you may have an internal hard part failing. Have you checked your trans fluid level, warm, in neutral with the engine running? What does the fluid look like? Is it cherry red or darker? I certainly would not drive it until you get this sorted out. If this were my trans, I would pull it out and get it thoroughly inspected & rebuilt.

 

[Chryco Psycho]

Check the adjustment of the throttle pressure lever . Kickdown lever .
The vibration could be that both 2nd & 3rd are trying to engage at he same time & fighting which is internal with band adjustments & or valve body .

 

[Xcudame]

Band adjustments, throttle pressure and any valve body issues can be done without removing the transmission from the car! I'd remove the pan, adjust both bands (rear band has to have the pan off) and adjust the throttle pressure. If I remember right without looking it up, stock throttle pressure is done with an 1)8 drill bit.

 

[dogmagolf]

Thanks Chryco and Xcudame. Just to confirm, you both mention throttle pressure lever, I assume that is outside of the transmission and you are referring to the kick down at the carb, adjusting linkage at that location? Or should I be looking at the trans (with pan out) for throttle adjustment as well? I will dig into the bands also, not super familiar with Auto Trans. Might look to take the trans for a rebuild in the spring as it was a drag car I imagine got beat up a bit at the strip.

Back to the kickdown, from what I have seen the adjustment is at the carb linkage. Any tips on where this adjustment should be at (specs) and how sensitive it is to tweaking (i.e. quarter turns/half turns etc.) I plan to play with this over the weekend and hope for no snow so I can test the adjustments.

Thanks again!

Jon .:R

 

[dogmagolf]

Wheels/balance has nothing to do with how the transmission is shifting. Sounds like the transmission is slipping. With the vibration you may have an internal hard part failing. Have you checked your trans fluid level, warm, in neutral with the engine running? What does the fluid look like? Is it cherry red or darker? I certainly would not drive it until you get this sorted out. If this were my trans, I would pull it out and get it thoroughly inspected & rebuilt.

Fluids all look good. I felt the same way, wheel balance doesn't make sense... That said, I plan to check the kick down adjustment and if that doesn't help, the trans will likely come out in the spring for a rebuild.

 

[Chryco Psycho]

Yes the kickdown linkage outside the trans can be adjusted , it should be fully back @ WOT , you can adjust it less so it does go 100% back at WOT but this will soften the shifts just to experiment .

 

[dogmagolf]

Some more follow up on this one. Had some nice weather this weekend, so I decided to run the car shifting manually to see what would happen if I took the "gear hunting" out of the situation and held it in 2nd gear. The vibration was still there, which leads me to believe it isn't related to the gear issue. In 2nd gear around 27-30 MPH it is vibrating heavily, but before or beyond that speed, it subsides. This has me thinking it is something out of balance at that specific rotating speed, either tires, driveline or even a balancer if the 440 has one. I will do some more digging and give updates, unfortunately bad weather is on its way for a few months.

 

[Mr Cuda]

It sounds like an engine combo/torque converter mismatch. Peak shake would come at 2200-2400 rpm.
Gear hunting could be throttle pressure or sticky governor.
As a test, run no kick down. Unhook at the carb for a couple block run.

 

[Cranky]

Do you have a FSM?? If not, why not? It doesn't cover modified stuff but it should get you to where you need to be. You mentioned it was a drag car earlier....any mods done to the trans? If you mentioned that I missed it.....