Shifting issue

[67 Coronet Conv]

Looking for help/advice on a shifting issue

1967 Coronet convertible
Mild built 440
727 trans
8 3/4” rear with 3.23

When I step on the gas and don’t let off, when the car shifts to 3 gear the motor just bogs down like it died. I let off the gas and lightly step on it and the car still has power and goes. Anyone have any idea why it would bog down when shifting to 3rd gear? This has happened to me more than a few times.

I’m thinking something with my tranny. Thanks in advanced

 

[Lefty71]

2-3 shift overlap maybe? Any work ever done to the trans, as far as you know?

 

[67 Coronet Conv]

2-3 shift overlap maybe? Any work ever done to the trans, as far as you know?

Not that I know of, just got the car 6 months ago. Working out all the bugs and this is one of them.

 

[oldkimmer]

Was it doing this when u first got it? Does it seem like it has a shift kit? Kim

 

[67 Coronet Conv]

it was doing it’s about 3 months ago when I was able to finally WOT the car. Doesn’t seem like it has a shift kit

 

[493 Mike]

Adjust the band/bands (if you want to drop the pan). Won't cost much or anything and eliminate the possible overlap issue.
Mike

 

[yella71]

make sure the kick down is adjusted correctly first. then check band adjustment also fluid level. go over all the basics.

 

[Ron H]

I'd also make a check of the shift points you have vs the factory spec's, what RPM you have when it up shifts to 3rd?

 

[dvw]

Are you saying it shifts 2/3 at to low of a rpm?
Doug

 

[Lefty71]

If the basics dont show any issues; fluid level, kickdown looks and measures factory spec, bands to spec, then I would try backing out kickdown band another 1/2 turn or so. If that makes no difference, then I'd say i'm on the wrong track and look for another potential issue like a valve body problem, or improperly done shift kit.

 

[67 Coronet Conv]

Thanks guys I’ll try all the above.

upshifts to 3rd about 5k rpm, then it drops to 3k in 3rd.

 

[threewood]

Are you sure it is trans related? It almost sounds like the result of fuel starvation if/when the bowls go dry. And it could happen at the same shift timing as well.

 

[oldkimmer]

Is it just slowing down or is it like the brakes are on? Kim

 

[67 Coronet Conv]

Motor bogs down when upshifting from 2nd to 3rd at WOT. Feels like the motor dies so I let off the gas cause somethings not right and then slowly step on it again and the car moves.

 

[Ron H]

Sounds like plenty of RPM before 3rd gear. If the trans seems to up and downshift fine, as I think I gather from what you've described, then as threewood said might not be trans related. The kick down rod adjust, far as I know, impacts the 1st and 2nd shifting, not 3rd, as I've played with and installing a shift kit in moderate setting. Sounds like possible fuel starvation if it's bogging down. Of course hard to offer tips since we're left to arm chair QB'ing, but some things to check would be carb related at least 1st. Assure you're getting ample fuel that can be thwarted by a bad filter or the carb filter if equipped or the fuel pump. Though if it is this, this gremlin should show up earlier than you describe. The other thing, more ahh concerning, is possible valve floating. I'll let ya google that to see of the symptoms sound familiar. I remember having this problem on my '67 GTO decades ago that caused me to lose a few street races back when. I ran wonderful until 3rd gear kicked in and then felt a deep-muted miss-fire and loss of power that I'd only get back after letting off the throttle. Anyway, if you can describe any of the symptoms you may have when you have bog down, if any, could be more telling...such as a miss-firing, etc. Not to add more possible demons; but there could be an issue with ignition/distributor but would rule out carb/fuel checks in the hunt. There are, as you likely know, simple checks on this before having to go deeper.

 

[67 Coronet Conv]

Thanks all for the input. After reading up on throttle linkage adjustment and looking at my set up, I got some questions concerns. See photos of my set up

-why is my throttle linkage and kickdown linkage on different on different throttle levers, shouldn’t they be on the same?

-return spring should be hooked up to throttle lever, but is hooked up to a different bracket on the carb.

-Holley calls for a throttle lever extension (P/N 20-7) if you are replacing a Holley carb. Obviously i do t have the extension, do I need it?

-looks to me that a I have an excessive gap in the kickdown linkage, does this look normal?

Cars specs
440 30 over
Edgelbrock RPM performer heads
Holley 870 street avenger
Mopar intake
Mopar cam 312 .590” (?)
Harland sharp roller rockers
10.5 Pistons (what the guy told me)
727 trans
3.23 rear end

I feel this car should haul *** but seems a little slow to me.

 

[493 Mike]

I'd say an award should be given to the person that set up your linkage! It seems every thing that could be wrong, is! You need the Holley/Mopar adapter. The throttle cable and KD link must be on the same pin, and throttle return spring also. There should be no gap showing between the pin and the slot in the KD adjuster and the adjuster needs a return spring.
Look at some of the engine pictures on this site and it will become clear to you.
Mike

 

[67 Coronet Conv]

I'd say an award should be given to the person that set up your linkage! It seems every thing that could be wrong, is! You need the Holley/Mopar adapter. The throttle cable and KD link must be on the same pin, and throttle return spring also. There should be no gap showing between the pin and the slot in the KD adjuster and the adjuster needs a return spring.
Look at some of the engine pictures on this site and it will become clear to you.
Mike

Thanks, after looking at the repair manual and a few other setups vs mine, mine just doesn’t look right. Hopefully this is the culprit. Hopefully have some time today to mess with it.

 

[Fran Blacker]

Everyone calls it Kick Down linkage, me included. It's really Throttle Pressure Control linkage. It increases the hydraulic pressure inside trans. You want full pressure at WOT.

 

[Ron H]

Looks like you might have found the culprit and also lucky you've not encountered binding throttle linkage. While it needs to be corrected, one of the checks (just for curiosity before disassembling) is to watch how the kick down is acting, or not as it should, with the way it's been setup, watching the action of the lever it's connected to on the trans with the engine off by opening the throttle all the way. The adjustment is to have the rod push the lever near to its complete travel (also not binding up by too much travel). There are some good videos on utube and can't recall the one I viewed; but the guys on it knew what they were doing with a late 60's RR. A matter of sifting thru those where some are for ****. My rough guess with this setup you have is the rod has little or looses its correct action on the lever. I'm no guru on this; just that I've messed around with this fixing effed up kick down adjustments a number of times; others here likely know more. Just my 2 cents.