Help rough shifting

[crodog72]

I'm new to classic vehicles and Bronco's but I purchased my First one this past Saturday. It's a 1972 Ford Bronco 4×4 that finished its Restoration in 2009. This vehicle is equipped with a rebuilt 302 Motor that has mild Cam, Holly Truck Avenger 4bbl, Edelbrock Manifold and Mallory Distributor. The front axle is a Dana 44 Chrome Alloy Axle with 4.56 Gears and a Powertrack Unit. The Rear End is a Ford 9” with 4.56 gears and a Detroit Locker. The Transmission is a rebuilt C4 with an Art Carr Shifter, New Torque Converter and Shift Kit. Truck is equipped with a high lift jack, Floor boards have a rubberized undercoating finish, Corbeau Ultra Wide Off Road Seats, and a Bikini Top.



Here's my concerns.....

When shifting from park to any gear it jumps pretty hard, and the same thing when it's driving and shift. Also it shifts from 1st to 2nd around 4500 RPM's and jumps pretty hard. Also, is there any good ideas for hiding wires below the Dash... I find it to be an eye sore. It seems to be geared more towards off roading but I just want to do a little Sunday riding and pick up groceries and beer in it. thanks in advance

 

[DJs74]

Congratulations on your purchase and welcome to CB.com!

As for the hard shifting from low to second, etc - that's probably a purposeful result that was done as a performance modification in the transmission (valve body) with the installation of a shift kit.

The 4500RPM from low to second can be adjusted with the vacuum modulator valve located bottom passenger side corner of the C4 - it will have a vacuum hose connected that runs up to the engine and attached to an intake vacuum port. It's tight in that area but if you can manage to get in there and inspect, you'll probably find a small screw inside the modulator port. If you want it to shift sooner and not quite as hard, adjust the screw counterclockwise and only 1/4 to 1/2 turns at a time. I would not exceed more than 2 - 3 full turns total out

As for the firmness when you put it in gear, could be a result of not enough converter. Do you happen to know what camshaft and what converter was installed?

Converter selection (IMO) is a direct result of what camshaft has been installed. Performance cams in the .500+ lift range (270s - 290s duration for example) usually require an above stock stock converter - for example: 2000 - 2500 RPM. if there is a decent sized camshaft and stock converter, that might explain why you get a hard shift from park to forward or park to reverse.

What RPM are you idling at?

I propose to check out the modulator, adjust and take it for a spin and see if things calm down. Also, I recommend an idle of 800 - 950 RPMs - if you are above that now and lower it, it will help your park to forward or reverse "bang"

Good luck,

DJs74

 

[crodog72]

First off thanks for the advice. I was wondering if changing the gears from the 4.56 to something less aggressive. When idling, it bounces from 1000-1500(is it normal for older engines to bounce when idling?. Also, while driving sometimes it will dies if I let off the gas (rarely but it has happened) I'm assuming that's just an issue with fuel pump/fuel filter/hose. The previous owner kept all the receipts so I will check to see what camshaft and converter was installed.

 

[Viperwolf1]

Too high idle speed will make it engage hard. Should be somewhere around 700 rpm at idle.

Does it always shift to 2nd at 4500 rpm? That should be about the highest rpm it will shift at when standing on the throttle. Maybe you don't have good vacuum to the modulator.

 

[Broncobowsher]

4500 RPM shift all the time sounds like the vacuum modulator doesn't have manifold vacuum or maybe the kickdown is jammed down. Either of those will give high line pressure and a high shift point at low throttle openings. Also a harsh engagement into gear.

Idle is way too high. As stated above a lot closer to 700 RPM, even into the 600 range is correct. Idle should be a lot more stable. Is that 500 RPM swing on it's own or when you into and out of gear? It really sounds like someone who doesn't know what they are doing has been messing with the carb and ignition. Hard to say what all is not set right. My guess is the timing is set by guess/feel and so is the carb. Probably just need a good day de-bugging the tune up and checking the basics.

Fill in your profile including location. There may be someone close with a timing light and a fresh set of eyes that could get this dialed in and running better.

 

[crodog72]

Will do on updating my profile. I went to bring it by a buddy's house and now the brakes are going out. When I push on the pedal when the truck is off it feels fine but when the truck is running there is no resistance pushing the brakes. I'm assuming this is also a vacuum issue? I leave for vacation today but when I get back I'll start putting ya'lls advice to use!! Thanks again everyone!