1988 Bronco C6 Transmission Trouble

[88 Bronco Nut]

Its a 1988 Bronco 351W with a c-6.

Ok. I will try to explain what is going on. I need Help on this I am at a loss.

First... I bought this truck and was told that the Trans Modulator was bad causing the trans to shift erratically. I bought a new one and put it in because when I took the hose off I had fluid in the vacuum line. So that was definitely bad. Trans still shifts back and forth from all gears without control.  

Then I thought maybe the Throttle Position Sensor... So I changed that. Still no change. Now since I put the TPS in the truck seems to run like crap and shift bad.

Ok so driving... Shifts into gears fine from park. Start to go and the truck accelerates but doesn't shift to 2nd till about 35mph... Then keep going and around 45 truck shifts to third if I let off the gas a little. If I barely step on the gas the truck slams down a gear and I need to accelerate over 45-50 to get it to and let off the gas and the truck shifts back up to 3rd. If I get it above 55 it runs in 3rd and doesn't shift back down unless I let it fall below 50ish. If I try to run the truck about 45 mph the truck will surge back and forth between gears even if I just keep my foot steady on the gas.

I was told maybe a cam shaft sensor? I don't have a clue. Anybody have any ideas of what I can check?

 

[Seabronc]

When you bought the new vacuum modulator, did you get one with the same color band as the original?

>-

 

[88 Bronco Nut]

The original one had no color band visible at all. The one I put in had a purple stripe, and was the only one that the auto parts store had. But I believe there is a green one out there some where, just not local.

 

[miesk5]

yo 88,

AS Fred advised on vac mod color;  This is by FORD

http://www.fordparts.com

7A377

(TM-43)
Auto Trans Modulator
5.8L 351 CID 8 Cylinders; Color - Green,
HOWEVER some claim it should have Black Band; as Andrew once wrote about his 89 C6 Bronco;

"...I have new information on the modulators, coming from the transmission specialist, and I mean specialist that rebuilt my C6 2 weeks ago.

The different color bands indicate the diameter of the rubber diaphragm inside the modulator. The two COMMON colors from auto parts suppliers are PURPLE and GREEN. These are for CARS. TRUCKS like OURS REQUIRE the BLACK banded modulator, likely from a transmission shop or dealer. This is regarding the mid/late 80's models, maybe more... Id venture to say any C6 with a slip in modulator.Again, PURPLE and GREEN are NOT the correct units to use, BLACK is the intended modulator as was designed for TRUCKS."

 

So, stop by a Ford dealer and confirm.

___________

Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19

http://broncozone.com/topic/14269-code-reader/?&pid=74587&mode=threaded

The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test.
Run it around to heat the engine up and shift thru all gears incl Reverse. Then turn off all accessories/lights, etc.

Make sure A/C is off and transmission is in Park (automatic) or in Neutral for a Manual & release clutch.

Do Key On Engine Off (KOEO) portion first.

And Post em here according to:
KOEO
&
KOER          
 

Throttle Position Sensor Testing, Replacement and Adjustment by Seattle FSB

http://www.fullsizebronco.com/forum/showthread.php?t=203080

 

 

[88 Bronco Nut]

OK so another problem... My smog pump is making a god awful rattle and it sounds like it is going to implode. Living in NJ the only inspection we have is emissions. If this is bad will it throw my emissions off so bad that I will fail? does anyone know if it makes sense to spend 100 to replace it?

 

[miesk5]

yo 88,

I doubt that it will pass NJ emission test.

Others usually buy a reman pump;

I know of two people that have rebuilt the pump; one pump worked for awhile, then failed again.

Rebuild
Source: by Steve  http://www.supermotors.net/registry/media/766465

Rebuild (but the pump failed again) - Great Info Though!
Source: by RickyB  http://fullsizebronco.com/forum/showthread.php?t=139144

Ricky wrote an excellent article w/ many pics;

"I found a new annoying noise. Using a 30 inch piece of 1/2" black hose I narrowed the culprit down to the smog pump, which was sounding a lot like six rocks in a rotating coffee can. After missing an Ebay Cardone #32-301 for like twenty bucks, and then getting prices from $60 to $150 and up, I decided to take mine off and see what I could do with it.....

.....Alright folks, here's a little update that I've been meaning to get around to. I'm sure a few of you probably know that the 'operation' was not quite as successful as I hoped. About 5 weeks after doing this my pump seized up-----totally. Thankfully it was on start up and not while I was driving, but it doesn't matter much now. Anyways after giving a lot of thought on what caused this damage the jury is still out on why it happened. It was either the new belt that I used that was still maybe an inch too short (because the tensioner pulley was almost all the way up, pointing to 3 o'clock) OR it was because I screwed up reinstalling the bearings, or more importantly the 2 fiberglass 'vanes'. But whatever the reason I've come to the conclusion that tearing into these smog pumps is probably not worth the time and effort----unless you have had actual experience at the factory itself..".

are some quick fix suggestions in it by Steve;

"Another option is to just spray some flowable grease into the 2 vent holes in the back. This one at 1:00: ...and this one in the center, which is recessed in the crescent....The outer one will **** the vanes where they slide in & out of the cylinder, and the center one will **** the rear bearings & the vane pivots..."  see Rick's article for pics


If the pump has already seized, begin with a HEALTHY dose of penetrating oil, followed by a shot of motor oil, then the grease.

Bear in mind that it WILL eventually work its way into the exhaust, so expect some smoke & elevated HCs for a while.

Preventing Smog Pump Seizures, General; "...Before installing replacement unit, [test check valve(s) for proper operation. Air should pass through valve only in one direction. These valves prevent exhaust gases from entering the unit. DO NOT install pump with a defective check valve. Check the PCV system for proper operation. An inoperative or defective PCV system allows oil and gas fumes to enter Smog Pump, causing bearing failure. Water contamination causes bearing corrosion, internal component damage, or housing failure. To help prevent this problem, carefully inspect all hoses, make sure fittings are secure, pump filters are not clogged, and the fan is not damaged. Be careful when washing the engine and, on low-mounted units, avoid driving through high water. Cover pump when washing motor..."
Source: by cardone.com

 

[Seabronc]

My .02, a green band will work just fine for the Bronco.  That is what has always been in mine. That is the problem, by the time the modulator goes bad the band has already worn off.   However, if you look hard enough there i usually some small trace of the band color on it somewhere.

>-

 

[88 Bronco Nut]

Seabronc... Believe me. I took that thing out and looked with a magnifying glass. I could not see any color on there. Now figuring that I bought this truck from a young guy who lied his ass off about what was wrong with it. I figure anything goes. I want to make this truck a sweet ride for going to the beach and fishing and just cruising around town.

 

[Seabronc]

I understand, just get a green band modulator and make sure the vacuum line is drained and clear.  That should clear up the shifting problem as long as there is nothing else wrong with the transmission.  You may want to put a new transmission filter in while you are at it and refill with fresh fluid.  I would also consider a bottle of LUCAS transmission treatment.  Don't over fill it.

Good luck,

>-

 

[88 Bronco Nut]

OMFG>>>>>>>>>>> I cant take this any more. So driving along almost home and the truck died. F@#K.......

SO the radio quit, then the interior lights dimed, started to buck and run like crap and the truck died. It did not over heat, I checked the hoses and nothing was super hot.

I was thinking alternator?

But then I thought that if the smog pump seized (read above) then maybe it wasn't allowing the belt to move and charge the system?

I have a brand new battery so I know that's not it.

Its late and dark and I cant see anything in the engine compartment. The belt is still intact so that's not it and if it was moving the belt (even slowly) then water was moving slowly, but still moving. Just not enough to keep the alternator charging the systems of the truck.

I need some input on this one.

PS: Anyone in the Little Egg Harbor NJ area that can pull my truck about 2 miles to my house? LOL.