C-4 downshift

[fyreduck1921]

I recently acquired a 76 Bronco Sport with a 302 and C4 automatic. The previous owner said the truck had hardly been driven in the 3 years he owned it. I have had it 3 weeks now and have put a few hundred miles on it around town. The other day it started with the following: It will NOT shift into 3rd gear until it is over 40mph, so in town where the speed limit is 30-35mph, it stays in 2nd gear. Also, when decelerating from higher speeds, it harshly downshifts from 3rd into 2nd at about 30mph. Transmission fluid is full and good color.
 

Any thoughts?
 

Thanks,

Steve

 

[Bully Bob]

Check the modulator on the pass. side of the trannie. (vacuum operated)

Is the "kick-down" rod in place & functioning..?

 

[fyreduck1921]

BullyBob,

Thanks again for the advice. The kick-down rod is not hooked up. It is zip tied to the valve cover. I need to contact the previous owner and ask him if he knows why. I've had the Bronco 3 weeks and the shifting problem just developed, so I don't think it's related to the kick-down rod, but considering I have already driven the truck more in the 3 weeks I've owned it than the previous owner did in the 3 YEARS he owned it, every idea is worth checking into!

Thanks,

Steve

 

[Bully Bob]

Hi Steve..,

If the carb isn't stock., it may not have the linkage for the kick-down.

However, I think there's ways to make it work but I don't have 1st. hand exp. with that.

The kick-down seems to help most with a "kick" for passing. 

The carb mfgr. may be able to help. 

Worst case would be a faulty torque converter. :glare:

 

[Seabronc]

If you have a Holley, they sell kick down kits.  Usually available at a good parts supplier.

Did you check the shift modulator as suggested?  Pull the vavuum line off it and check for trany fluid in the line.  If so, the diaphram is bad.  Also make sure the modulator is connected to main vacuum.

I you have to replace it, be careful not to lose the rod in the end of it.  You will need to know the  color of the band around it in order to  get the correct replacement part.

>-

 

[fyreduck1921]

Seabronc and Bully,

I crawled under the Bronco and honestly wasn't sure what I was looking at. All I saw on the transmission were solid steel lines. When I told my uncle about my shifting issue today, he also said shift modulator, so he's going to come look at it Saturday.

I found a kinked vacuum line at the rear of the engine. It was about 4 inches long and went from the vacuum tree at the rear of the intake manifold to a hard steel line near the firewall. Now that I think about it, this might be the line that runs to the tranny. Anyway, I repositioned the steel line to take the kink out, of the rubber line, but no change in the shifting. While the rubber line was off, I did put my finger over the vacuum tree and confirm that it is pulling a vacuum.

Anyway, I just wanted to update you guys. Thanks for the help and I'll let y'all know what else I find.

Steve