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66-96 Ford Broncos - Early & Full Size

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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 post-20660-0-74679300-1407265546_thumb.j

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Hi Crodog.., welcome..!

---- Nice rig..!! ----


Off the top., I'd say your problem is the shift kit.

I'm not up on automatics but I would guess a good trannie shop could detune/reset it to be more comfortable.

The down-shift (kick down) rod that hooks to the carb. may need adjusting as well.

(Someone correct me but aren't "shift kits" mainly for drag racing.?)


"it shifts from 1st to 2nd around 4500 RPM's"

This seems wrong on many levels & maybe even dangerous.



Another possibilty is the modulator on the passenger side of the trannie. They can lose vacuum or leak internally

& cause a hard shift.


"is there any good ideas for hiding wires below the Dash... I find it to be an eye sore."

Add a pic of this..., someone may have some ideas after viewing.


P.S.  I removed your double post.  That can only create confusion. 

This post in "Tech Support" will serve you well.

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Yo CR,


AS Bob advised on the Vacuum Modulator Pull the vacuum line off the mod. If fluid comes out of the vacuum line your modulator is not good.

See if the modulator has a colored band on it; replace w/same color banded modulator.  Also inspect vacuum hose from Mod to the steel line up to manifold.



Park it on a firm, flat surface. Set the shifter in the "Park" position and remove the ignition keys. Place wheel chocks under the rear tires.

Remove the rubber hose from the modulator nipple by pulling it straight back by hand.


Insert a narrow shank flat head screwdriver into the nipple until it seats into the slot of the adjustment screw.


Turn the modulator adjustment screw in a clockwise direction with the screwdriver to firm up and delay the up-shift of the transmission. Do not adjust the screw more than four turns in either direction.


Turn the adjustment screw in a counterclockwise direction to speed up and soften the up-shift.

 Test drive it. Make any further adjustments by repeating Step 4 through 8.

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One more Trouble Shooting


Check fluid level and condition

Make sure kickdown rod or cable is not binding
Turn kickdown rod adjusting screw out 1/8th" inch
Check vacuum at modulator; around 18" vacuum w/engine at normal op temp
ADJUST modulator screw

Clean governor
Replace valve body

Make sure the vacuum hose to the modulator is not routed where it could be kinked or pinched


Check local library for on-line access to Chilton or All Data; ours has All Data, but in-library access only; CONFIRM ALL adjustment INFO BELOW, please


With the engine stopped, place the transmission selector lever at the steering column in the N (neutral) position for models through 1967, or the D (drive) for 1969 and C4 and C6 later models. On the later C4 and C6 models, make sure the lever is against the D stop.

On 1978 and later models, it will be necessary to hold the lever in the D position by suspending an 8 lb. weight from the end of the selector lever.


Exploded view of the shift control linkage-1969-73 models (1972-73 models have two locknuts on either side of the trunnion)

Loosen the shift rod adjusting nut at the transmission lever.

On models through 1967, place the transmission lever in the N position (4th detent from the rear). On all other models, place the transmission lever in the 2nd detent from the rear.

On models through 1967, insert a 1 / 4 in. gauge pin through the steering column shift rod actuating lever and the steering column shift tube bracket to hold the shift rod linkage in the N position.

On 1974 and later models: With the selector lever and transmission manual lever in the required position, turn the trunnion so that it slips into the hole in the transmission lever and tighten the adjusting nut to 12-18 ft. lbs. (16-24 Nm). Do not allow the rod or shift lever to move while tightening the nut.

On models through 1967, turn the trunnion 1 full turn counterclockwise to lengthen the rod. Connect the trunnion to the lever. Remove the gauge pin.

On 1969-71 models, turn the trunnion 4 full turns counterclockwise to lengthen the rod. Connect the trunnion to the lever.

On 1972-73 models, lock the trunnion without turning it. Connect the trunnion to the lever.

Check the operation of the shift linkage.



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I'm back in town and will start trying these suggestion out first thing. Thanks for the advice and I'll keep ya'll posted on how everything turns out

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Over 100 folks have viewed/followed your post. :-B

So please do post your tests, checks, results. Doing so may help several others with similar issues.

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I noticed that when I put the truck in gear, the rear differential wants to twist a lot. It looks like the previous owner home made a bar to attach to the frame to try to reduce this twist... Anyone heard of someone doing something like that?

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Have not seen a homemade one but there are several on the market at the EB stores.

I have one (set of two).., it's an older design.


The way your rig shifts, I can see why he did that..!!

Shoot us a pic of that/those traction bars. (that's what they're called)  We'll see if they're homemade.

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If you are talking about twisting forward or rearward, then you are describing axle wrap.  That could very well be due to weak leaf springs or loose U-bolts, especially if you are not actually accelerating.  Axle wrap generally experienced by drag racing vehicles and not normal for street vehicles. That bar may be to counter the wrap.  Like BB said, a picture would be helpful.  


Check this out from Wild Horses http://www.wildhorses4x4.com/product/Wrap_Trap/bronco_rear_axle




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Yep.., as Seabronc says "axle wrap"

I was being a 'lil vague.

I would add that all EB's have a bit of axle wrap. Add a lift & big tires & it's compounded.

Even with all new suspension parts.., this is likely to rear its ugly head.

Also, axle wrap brings about the well known EB "Bronco clunk"  when taking off from a stop.

With your trannie issues it's going to be more obvious.


The main reason is the EB's came from the factory with a "spring-over-axle" set-up


The pic Seabronc is showing is the "latest" design & works best.

The original/first design to stop this was on drag vehicles with slicks, to stop wheel hop.


I had slight axle wrap when I put my small lift on (all new springs). That's why I installed the older 2nd or 3rd generation traction bars (they called them that back then)  made by James Duff. They work but no longer "state of the art" like the design above.

The only slight drawback is these (Wrap Traps) req. welding.

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