My father has a 87 Bronco with a 302 Multi-port Injection. It is an automatic (with OD) and has push button four-wheel drive. The truck runs great from idle to wide-open, but it is very weak. It has to downshift to even pull a small hill, and pathetically struggles to pull a boat. Even in drive (not OD) the truck is weak. He loves this truck, and I'm trying to help him out (since he doesn't know much about vehicles), as he wants to improve the power. This has me stumped, since it runs great (no skipping, smoking, knocking, etc). We had the fuel rail rebuilt and all filters are fresh, as well as all ignition components. My thoughts are that either the gear ratio is too high or somehow the power is getting lost through the tranny. I know the 302 won't have as much power as a 351, but I've had small V6's that pulled much better. Any thoughts? Thanks in advance!

 

Welcome to FTE daddydcs! The gearing in our broncos is very crappy in my opinion. There should be a small tag affixed to the rear differential. That tag will have a specific code on it. With that code, we can tell you what gearing you are running. I know MOST broncos come from the factory with 3.55's. They are pathetic to say the least. They do not belong in a bronco. The mechanical advantage (in this case, lack thereof) is maginifed when you are towing. As you have said, you have run V6's with more 'seat of the pants' power...this could certainly be true. Tire size, tranny gearing, rear differential gearing, etc, all play a part in how the power is perceived to the driver. What size tires do you have now? How many miles on the rig? The best bet for more seat of the pants power is to install lower gearing. That will make the rig come to life! The downside (and yes, there is normally one) is that can be mucho expensive if you dont know how to do it yourself. If I had to venture a guess, I would say somewhere in the 1200-2000 dollar range . I hope to see you around the boards.


Rich

 

Thanks for the welcome! The Bronco has 31 inch tires and about 160K miles on it. I will check the gears/tag as soon as he gets back in town. If he does have the 3.55s, then we'll probably look at some lower gears since he will be retiring in a few years and wants to get him a small camper to pull. I'm trying to get him fixed up now so it'll be ready for him when he needs it. I love this forum, and am partial to Broncos... I have thought of getting one myself! Thanks again!

 

Drop a 460 in there!

Edit: I just wanted to say that because before this thread is over, someone is going to say swap in a 351W and someone else will say stick in a 460.

 

We have talked about putting a 351 in there, but I feel like there are other problems that we need to address first (like the gears if they're 3.55s). The big 460 might be a little more than he could handle! What rear end ratio would yall recommend for a 302 (and a 351) with 31-33" tires with an OD tranny for pulling campers, pontoons, etc.? Any suggestions?

 

I personally love how 31"s and 4.10s feel. That is the gearing that will be going into my bronco when my bills are paid (long time....). I have found that the jump from 3.55 to 4.10 is about 800 rpms at 65mph. My bronco doesnt really feel powerful on the highway until I hit 80...and we know how much more room there left on the speedo . The rpms at that speed are roughly 800 over the 65mph reading.....so the 4.10s would put me right where I want to be for crusing on the highway. The only drawback to having the power on demand is that your efficiency (mpg) can suffer on the highway. I would rather lose a mpg or so to have a vehicle I can enjoy.


Rich

 

4.10 gears! Its a good all around gear for highway driving and some off-roading

 

yes 4.10s i have them in mine and its also a 302, and my dad uses it to tow a 70's 28ft skipjack (fishing boat) between 4-6 tons i believe, i have 32" tires on my rig also and with the help of a little loose gravel i heard a chirp when i took off real quick, lol. that was before i rebuilt it and fixed her up, i think it had about 400k on it

 

Thanks for all the advice... it sounds like 4.10s are what I'm looking for. As soon as Pop gets back in town we'll check it out and I'll let yall know what we find. Thanks!

 

I don't think the problem with Bronco's is the gears. The engines are turds. The 302 and 351W leave something to be desired, but they have great potential. Change the cam, heads, etc

The weight of the Bronco alone causes the Bronco to struggle, let alone if you are towing something.

 

you should start off buying a nice pair of headers and a good muffler

 

For low end increase, you want long tube headers!

 

Thanks for all the input/help! I've got some good ideas on what to check first! I'll post a thread with the same title when I find something out in case yall want to know what I find!

 

Something else to consider is plugged up catalytic converters. My 86 / 5.0L was way lacking in power before I put in a new motor and didn't get any better after. Used a remote temp/thermometer(the laser kind) and the second cat in line was 200+ degrees hotter than the other. I cut off the muffler, rammed a steel bar into the cat to break everything up, welded on a cherry bomb and wouldn't you know it. More power. Alot more power. Headers and high-flow cat w/muffler is next on my to do list. Another way to check is to undo the flanges where the exhaust manifolds connect to the exhaust pipes and run around a little bit. If its the cats or anythng else downstream this would be a good indication. You will have a very noticable power increase. Someone else may say different but this is what found out my power issue.

 

I just had a similar problem to ChargerFan. Had new engine put in (2) yrs. ago. Just seemed like truck did not want to run. I wanted to replace passenger side exhaust manifold, so I bought a set of 2 to 1 exhaust pipes and a cat. conv. Put the pipes and cat on and truck runs much better. If you do a search on "GOOGLE" by clogged catalytic converter you should get back a lot of ways to check a cat. conv. A couple I remember are the temperature in front of the cat. should be approx. 100 degrees cooler than behind it, read with a hand held temp gun and there were some pressures stated so that if you have the proper pressure gauge you can check for back pressure thru the O2 sensor port. Take the O2 sensor out and read the pressure. Another symptom I had was drop in gas mileage. Mine dropped off about 3 mpg and that's a lot when it's not that good to start with.

Good luck,
guzzler96