better highway performance
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New User
Joined: Jul 2003
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From: Junction City
better highway performance
My freind has a 1984 F150 with a straight six, 4-speed manual tranny with a granny low 1st, and 3.55 gears. He can only go about 60-65 on highways. We are planning on taking his truck cross-country and I was wondering what we can do to get better speeds? An overdrive or swappind trannys? Just wondering what other people have done. Thank You.
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Joined: Sep 2003
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From: Houston TX
If he's got a 3.55, he should able to do 70 no problem. The rpm's will be cranking on up though. I've got the same deal with a 4.10 rear. I'm planning to eventually change the t-18 to an AOD. I've been scouting all the alternatives, and the AOD seems to best for my specific truck. It's got about the highest O/D of all the common O/D tranny's. ".67" Will drop your rpm a 1/3 on the highway. IE: if you do 3000 at 70 mph, with the .67 o/d you would turn appx 2000-2100 or so. 
MK
MK
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Joined: Mar 2003
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From: Colorado
Hello neighbor, (Castle Rock)
She sounds a bit tired - have you tried a full tuneup.? Checked compression? I run the same gears & tranny - with 31's.
I'm spinnin' 3300 @ 85 mph & 4,000 @ 108 (???).
I looked into tranny swap/ OD... 2-3X expensive compared to a 4bbl/intake/EFI exhaust. My rebuild only has 30K miles on it though...
She sounds a bit tired - have you tried a full tuneup.? Checked compression? I run the same gears & tranny - with 31's.
I'm spinnin' 3300 @ 85 mph & 4,000 @ 108 (???).
I looked into tranny swap/ OD... 2-3X expensive compared to a 4bbl/intake/EFI exhaust. My rebuild only has 30K miles on it though...
Posting Guru
Joined: Apr 2003
Posts: 1,153
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From: Venezuela
The basic problem is not power... the problem is too high RPM for long, long trips... it will destroy the I6 beffore end the trip.
1º Upgrade to AOD tranny and 3.55 rear axel OR
2º Change Rear axel ratio to 3:1 (Will lost torq for climbing but get same speed with lower RPM) OR
3º Install and aftermaker overdrive after tranny OR
4º Upgrade to a manual 5 speed tranny like mazda
Regards;
1º Upgrade to AOD tranny and 3.55 rear axel OR
2º Change Rear axel ratio to 3:1 (Will lost torq for climbing but get same speed with lower RPM) OR
3º Install and aftermaker overdrive after tranny OR
4º Upgrade to a manual 5 speed tranny like mazda
Regards;
Senior User
Joined: Mar 2002
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Scout, Your friends problem is with the engine and not the gears. Taller tires or different gears will not help. I have a 78 F-150 4x4
I-6 with 3.50 gears. It has over 200,000 miles on it and has no problem doing 85-90. Many in here equate taller gears to more speed or better fuel economy. This is not always the case.
I-6 with 3.50 gears. It has over 200,000 miles on it and has no problem doing 85-90. Many in here equate taller gears to more speed or better fuel economy. This is not always the case.
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Joined: Mar 2003
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From: Colorado
Originally posted by broncr
Hello neighbor, (Castle Rock)
I'm spinnin' 3300 @ 85 mph & 4,000 @ 108 (???).
Hello neighbor, (Castle Rock)
I'm spinnin' 3300 @ 85 mph & 4,000 @ 108 (???).
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Junior User
Joined: Oct 2003
Posts: 65
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From: virginia beach
I just got a 92 150 I-6 with 31's and it seems to turn out speeds just fine it takes a long a**time to get there but it does alright. I dont know if i'd take it croos country.
good luck
good luck
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Postmaster
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From: Muskegon, MI (home)
Originally posted by broncr
And so back to the original post - I'd suggest you check compression & or do a full tuneup - it sounds obvious the old 300 is having problems if it can barely do 65 while so many others are.
And so back to the original post - I'd suggest you check compression & or do a full tuneup - it sounds obvious the old 300 is having problems if it can barely do 65 while so many others are.
Senior User
Joined: Jun 2003
Posts: 188
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From: Wesley Chapel, FLA
If the motor seems to run fine otherwise then make sure all the throttle linkage is adjusted and working correctly. It could simply be your friend is not getting full throttle. With a 3.55 ratio freeway speeds should be easy. With an unmodified six it may take a while to get there but it should not be any problem doing it.
As for not taking the truck on a trip that is nonsense. I have a 3.70 ratio and I will take any trip anytime and always have during the 21+ years and 300,000+ miles I have had my truck. The truck has been in all but 8 states and it's going to all of them sooner or later. Except Hawaii. Won't be driving there anytime soon.
As for not taking the truck on a trip that is nonsense. I have a 3.70 ratio and I will take any trip anytime and always have during the 21+ years and 300,000+ miles I have had my truck. The truck has been in all but 8 states and it's going to all of them sooner or later. Except Hawaii. Won't be driving there anytime soon.
Last edited by rmt; Oct 29, 2003 at 08:40 AM.
Post Fiend
Joined: Mar 2002
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From: Bonita Springs FL
The way you guys talk, it makes me think there's something really wrong with my Bronco.
It's got a 3.55 rear, and it can hardly get out of it's own way. I was able to wind it up to 75 once, but I was in Nevada and had a LONG stretch of road to do it on. This is a far cry from those who say they've been to 100 in their trucks.
I've done the full tune-up (including timing & PCV valve) and compression reads about 120-130lbs in all cylinders. I really would like to get this truck running the way it should be. Where do I start looking next?
It's got a 3.55 rear, and it can hardly get out of it's own way. I was able to wind it up to 75 once, but I was in Nevada and had a LONG stretch of road to do it on. This is a far cry from those who say they've been to 100 in their trucks.
I've done the full tune-up (including timing & PCV valve) and compression reads about 120-130lbs in all cylinders. I really would like to get this truck running the way it should be. Where do I start looking next?
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Joined: Feb 2003
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From: Muskegon, MI (home)
andym...
How many miles do you have on your Bronco? You know I wonder if one or both of your cats are clogged, if they are cut em off. Mine sure gained a lot of pep when I did that to my 84. A few other bolt ons that helped were adding a high output coil, K&n air filter, and Flowmaster muffler. You could try advancing your timing a little, that will definately give it some more punch.
How many miles do you have on your Bronco? You know I wonder if one or both of your cats are clogged, if they are cut em off. Mine sure gained a lot of pep when I did that to my 84. A few other bolt ons that helped were adding a high output coil, K&n air filter, and Flowmaster muffler. You could try advancing your timing a little, that will definately give it some more punch.
Elder User
Joined: Mar 2003
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From: Colorado
Originally posted by andym
The way you guys talk, it makes me think there's something really wrong with my Bronco.
This is a far cry from those who say they've been to 100 in their trucks.
The way you guys talk, it makes me think there's something really wrong with my Bronco.
This is a far cry from those who say they've been to 100 in their trucks.
I agree with prior posts - look at the linkage - are you getting full throttle? Cat's do plug and can drastically restict any engine. You probably have some kind of problem - but the 300-6 /120-130 compression indicates it not REALLY bad. I've seen a lot of problems solved here at FTE - hang in there... you'll get it...
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