tachometer
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Junior User
Joined: Jun 2006
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From: SW MN
tachometer
My 1969 F-250 with a 390 doesn't have an tachometer and I want to put one in because it is geared very lowly. It has a 3 speed tranny with 4.10 gears in the rear end so the rpms are way up there going down the highway. I put one on a chevy pickup before and it was very easy because it just pluged it into a certain spot on the distrubuter (very simple). Is this the same on this because I can't find anywhere on the distributer where it plugs into?
Thanks
Thanks
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Originally Posted by Redmanbob
maybe a governer would be better ?
I had a governor once. It was when I was about 4 years old and my dad thought it would be best to have one on my little 70cc 3 wheeler. Soon as I started realizing this, I fixed that damn problem. 
Actually, I hear ya oscar_007, I've got a '75 highboy with 4.10s and that thing revs high going down the freeway. I just keep her at 60-65. I might be a little late getting there, but I ain't in no hurry....
I might end up doing the tach thing too. Just a nice little one that mounts on the steering column is what I'm looking to get.
Postmaster
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I installed the tach wire to the negative side of coil as was mentioned. My tach works good.
Actually, I hear ya oscar_007, I've got a '75 highboy with 4.10s and that thing revs high going down the freeway. I just keep her at 60-65. I might be a little late getting there, but I ain't in no hurry.... I might end up doing the tach thing too. Just a nice little one that mounts on the steering column is what I'm looking to get.
I hear both of you, my 1975 F250 hi boy does the same.
Originally Posted by mswift
Actually, I hear ya oscar_007, I've got a '75 highboy with 4.10s and that thing revs high going down the freeway. I just keep her at 60-65. I might be a little late getting there, but I ain't in no hurry.... I might end up doing the tach thing too. Just a nice little one that mounts on the steering column is what I'm looking to get.
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From: Long Island USA
Yeah, the 4.10's in the Highboys are kinda high. With 33" BFG's, mine wasn't TOO bad...
Hmm... what speed is that when you hit 6000 RPM's in 4th gear?
Just being sarcastic.
An easy way to change gearing is ... change the tire diameter.
Hmm... what speed is that when you hit 6000 RPM's in 4th gear?
Just being sarcastic.
An easy way to change gearing is ... change the tire diameter.
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From: SW MN
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From: "Islander"
Without tire growth on 33" tires @ 6K will get ya 143+ mph.
I've been to 5,400 with 32.5" tires at 5,400 for 127 mph in the CS.
I've been to 5,400 with 32.5" tires at 5,400 for 127 mph in the CS.
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I've got a question, y'all can prolly answer.....
Krewat got me thinking when he mentioned 4th gear. My truck is a '75 Explorer Highboy, 4.10 and a factory C6. With that in mind, what would swapping out to a 4 speed do? I'm not going to do it, as this is my only automatic rig, but are the ratios the same. Meaning being in 4th gear cruising down the freeway at 3000RPM, as opposed to being in "Drive" cruising down the freeway at 3000RPM.
Thanks...
Mike
Krewat got me thinking when he mentioned 4th gear. My truck is a '75 Explorer Highboy, 4.10 and a factory C6. With that in mind, what would swapping out to a 4 speed do? I'm not going to do it, as this is my only automatic rig, but are the ratios the same. Meaning being in 4th gear cruising down the freeway at 3000RPM, as opposed to being in "Drive" cruising down the freeway at 3000RPM.
Thanks...
Mike
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From: "Islander"
With all things being equal besides transmissions the auto will have torque converter slippage I would guess app 300 rpm's, more under heavy throttle and higher mileage as it gets loose with mileage. years ago a auto with 3.79's was the about the same as 4.11's in a manual on the engines rpm's at a given highway speed. Autos eats more hp than a manual which is all over the board as I have read as much as 60 hp, all guessing i'd say.
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From: "Islander"
Are you talking 3 speed only or a T-18 / 435 as a giant 3 speed with the non synchro granny low?
With your 4.11 gearing and tires you should be taching 2,721 @ 65 mph, should you go to 3.79 gears 2,509 @ 65 mph.
Your below the 3,000 zone which will eat the fuel but again you only have a 390 and come up short of torque available with wind resistance alone.
That is where 3.54's with a manual box and a 3.98" crank comes into play, 2,344 rpm @ 65 mph with a motor built for low end torque. I have broken into the 15 mpg range a few times with a 414, 3.54's with a C-6.
With your 4.11 gearing and tires you should be taching 2,721 @ 65 mph, should you go to 3.79 gears 2,509 @ 65 mph.
Your below the 3,000 zone which will eat the fuel but again you only have a 390 and come up short of torque available with wind resistance alone.
That is where 3.54's with a manual box and a 3.98" crank comes into play, 2,344 rpm @ 65 mph with a motor built for low end torque. I have broken into the 15 mpg range a few times with a 414, 3.54's with a C-6.
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I have a 2 1/2 in tach mounted on my dash. Its a cheap one and works fine.
Look at a Jegs magazine. They have tons of tachs.
3 3/8" Sunpro super Tach-$50
3 3/4" Autogage Tach-$50-$60
2 3/4" Autogage Mini Tach-$65
Look at a Jegs magazine. They have tons of tachs.
3 3/8" Sunpro super Tach-$50
3 3/4" Autogage Tach-$50-$60
2 3/4" Autogage Mini Tach-$65
