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Discussion Starter #1
Hi!. I have a ford bronco 1991, has a 5.0L engine with 2 bbl carburetor, it also has the AOD transmission with the 8.8" rear end with 3.73 gears, 31" tires on 15 "wheels. The problem is that highways do not get high speeds at low rpm , being that to reach 65 mph (100 kph) I bring the engine up to 2500 rpm, so the engine feel forced labor. from what I researched, the rpm to achieve that speed should be about 1500. I will appreciate much your comments to find the solution to my problem. Thanks. :thumbup
 

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Roller rockers are gay
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1500 pretty low. you have 3.73 gears, typical stock is 3.55...you're gonna turn faster. but 2500 does sound a bit high. are you SURE it's shifting into fourth?
 

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Sounds like you are not getting into overdrive. Are you positive on the gear ratio? If info is correct you should be 1750RPM @ 65MPH. How was MPH determined?

You shouldn't be laboring at 2500RPM, sounds like you have something else going on there.
 

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Discussion Starter #4
I'm sure the transmission shifts all gears from first to fourth without problems, the differential ratio is 3.73 and the values ​​of rpm and mph are indicated by the instrument cluster.
 

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Roller rockers are gay
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i agree with sl210, i don't think you're getting into OD. do you have three distinct shifts after you accelerate to 65mph from a stop?
 

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How the hell did you get a carb on that thing?
thats what i want to know

AOD
This transmission is a rear wheel drive 4 speed automatic and shift timing is controlled by a throttle pressure rod or cable that connects from the transmission to the carburetor or throttle body. Listen up again because this problem happens all the time. Always check the throttle pressure rod that goes from your transmission to your carburetor or throttle body linkage.

This controls shift points and often the plastic little bushings that hold it on, get brittle from the heat, breaks into pieces and falls off causing symptoms above. Good Luck!
I recommend that you always replace the boost valve when rebuilding any Ford transmission.
 

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He is in Venezuela, it may have come stock with a Carb. :shrug

Can you post a video of your bronco accelerating from a stop to 65MPH?
 

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doesnt sound like he is getting into over drive. sure its not a c6 tranny. rpm's sound alittle high even for that. think someone changed out gears, and it maybe 4.10 gears not 3.73.
 

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My 87 ran @2500 rpms at 65mph and when I had it checked I was told that it was normal... The opion was reinforced by the emmision testing in Harris county tx (pre obd2/dyno testing) as the sniff test was done at 2500 rpms as they stated it was the avg overall rpms for the vehicles in the county. Now this it what I have been told. In no way go by my info just passing down info I got..
 

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Discussion Starter #11
I have three shifts from stop to 65 mph. the first shift at 15 mph, the second at 25mph and the third at 45mph. I told you that the gears on the diff are 3.73 (11 pinion / 41 ring) I purchased at e-bay; but I think it was a mistake, The carburetor is a modification of the change from a 4.9l engine that had previously to the current 5.0L, and given that Venezuela is not accessible by locating all the parts (electrical branch, computers, etc.) to leave with electronic injection, I had to put carburetor. The TV cable and the bushings are in perfect condition. The transmission is an AOD (in the oi pan says ford METRIC Automatic Overdrive), and again, I told you the transmission works in great condition.
 

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Discussion Starter #12
I want to see something: if I change the ratio of 3.73:1 to 3.08:1 differential will see an improvement in speed and engine rpm?
 

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I bet the TC is not working. When you get on the highway get up to speed around 65mph. Then tap the brakes and let off of them. The rpms should go up when you do this. If they dont your TC isnt working.
 

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Discussion Starter #15
I bet the TC is not working. When you get on the highway get up to speed around 65mph. Then tap the brakes and let off of them. The rpms should go up when you do this. If they dont your TC isnt working.
I don't have a transfer case, my bronco is 4x2
 

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Discussion Starter #17
He is referring to TC as the Torque Converter.

You converted to V8 from an I6? Did you reset the Tachometer?
The tachometer was installed after the conversion with the dashboard. This was originally dashboard of a pick-up f-150 with 8-cylinder engine. Will test the torque converter
 
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