HELP!! I'm new to forums, threads, and this kind of web site in general. So please be kind if I seem totally out of my element here.....

I have an 88 bronco which I truly love. I bought it from my son who couldn't afford the required fixes, who bought it from a man that had left it sitting in a garage for over 10 years. So far I've been pretty much on top of things until I recently started getting two totally different opinions on the same problem. Unfortunately I need to fix the problem as soon as possible and have already spent over $500 on other bronco issues in the past five days. I'm hoping there are a lot of you out there who have experienced my problem.

I have a C6 transmission and a 351 windsor engine. When I start the bronco and put it in drive, sometimes it works fine. Other times it doesn't move. If I hit the gas a little harder, it finally starts to move, but either very slowly or else it starts to shudder and then move slowly forward. I stop for some reason and when I step on the gas again the same thing happens. But a lot of times, after you drive it awhile, it's ok. I'm also getting a little bit of a chattering sound when it's acting up. Other times, I start it exactly the same way and it works fine.

From what I saw at one forum, people were talking about how a modulator solved all their problems when they thought they had transmission problems. The mechanic I use (when my husband can't work on it), says he can put in a new modulator, but it would be a waste of money because the problem is internal with the transmission.

Any thoughts out there?

 

Welcome to FTE and the Big Bronco Forum. We hope you enjoy the site as much as we do. The folks here are really some of the most knowledgeable and friendly I have ever encountered. We will do our best to get you the most accurate info we can muster.

First thing to check is the condition and level of the fluid in the transmission. The fluid that comes out on the dipstick should be bright red/magenta and appear clear on the stick. Follow the instructions on the dipstick when it comes to the procedure to make certain for the proper level. Sticky internals or low fluid levels will cause these symptoms as well. Whatever you do, avoid additives that clean out the transmission if you aren't sure that the fluid was changed on a regular schedule. I know it may sound counter-intuitive but when it comes to the transmission, cleaning out an old one too well WITHOUT rebuilding it can actually cause problems. A fluid and filter change would be the place to start if needs be.

Second, if the fluid is not the problem, second guess your mechanic. The shift modulator is a vacuum-actuated device that can and does fail. Even if it turns out that doesn't fix the problem, it' still less expensive to find out by replacing it before you get into tearing down the transmission itself. (A transmission rebuild will include replacing this device anyway).

The C6 is arguably the most reliable automatic ever put into the Bronco and they don't cost a lot to rebuild should it become necessary.

 

How many miles are on the tranny?

Do the checks and fixes in this order:
1) fluid level
2) fluid quality (color, smell) , and do a fluid change if it's really bad
3) replace vacuum modulator
4) tranny repair or replacemnet

 

Thank you so much for your input! Here's what happened. I went thru the steps listed. Checked fluid levels, did the transmission flush, and then because it was such an easy and cheap possible fix, changed out the modulator. I have to tell you, I am 52 and claustrophobic. I still can't believe I was under the bronco on a creeper doing this. Anyway, it looks like the modulator solved the problem (so far). After putting it in, we took a 280 miles round trip and the bronco drove WONDERFULLY. I can't wait till I see the mechanic the next time.....

The next issue is a vacuum hope we discovered that isn't attached to anything. See next post.