Quick Noob Question on Speed
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Freshman User
Joined: May 2011
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Quick Noob Question on Speed
Hello everyone,
Just recently got my dent and I'm younger and somewhat new to the older-vehicle scene.
My truck is a '78 Short Box 4x4, 4 speed. 351m 400 engine with T18 trans.
No problems at all with driving around town or anything but I will be taking a longer distance vacation soon requiring interstate travel and have a question.
When I put it into 4th gear, it sounds good up until around 60. I don't have a tac, but RPMS are really high and it sometimes makes me nervous.
Speedo goes up to 85 but I've never had it up that high.
I guess my question is; Is it normal for the dents to get really loud/lots of RPMS at higher speeds?
If this is a stupid question, I apologize. I guess I'm used to the newer cars where you can barely hear the outside when driving 60+.
Also, is it OK to maintain those speeds even with the high RPMS and loudness?
Just recently got my dent and I'm younger and somewhat new to the older-vehicle scene.
My truck is a '78 Short Box 4x4, 4 speed. 351m 400 engine with T18 trans.
No problems at all with driving around town or anything but I will be taking a longer distance vacation soon requiring interstate travel and have a question.
When I put it into 4th gear, it sounds good up until around 60. I don't have a tac, but RPMS are really high and it sometimes makes me nervous.
Speedo goes up to 85 but I've never had it up that high.
I guess my question is; Is it normal for the dents to get really loud/lots of RPMS at higher speeds?
If this is a stupid question, I apologize. I guess I'm used to the newer cars where you can barely hear the outside when driving 60+.
Also, is it OK to maintain those speeds even with the high RPMS and loudness?
Cranky Old Guy
Joined: Mar 2008
Posts: 3,562
Likes: 6
From: Raphine, Virginia
Engine is naturally going to rev higher than newer vehicles. You have a 1:1 final drive where just about everything now has overdrive. Gear ratio in differential will contribute to that. Lower the gears, higher the rpms. Tire size can play a factor also. It would not be abnormal for it to be turning 3000 rpm at interstate speeds where a new vehicle might be running 1800-2000 rpm. These vehicles were made when speed limits were 55mph and designed for that.
Fleet Owner
Joined: Dec 2009
Posts: 20,678
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From: NorCal
"Loud" is relative. ...About the only insulation these rigs have is the cardboard used for the headliner, a firewall pad, and a rubber floor liner or carpet.. Sound deadening (and evidently rustproofing) for working trucks was only a concept back in the day!!!
But hey, we've got the survivors so keep'em on the road. Congrats on your new-to-you 4x4 and welcome to the Dentside brethren.
But hey, we've got the survivors so keep'em on the road. Congrats on your new-to-you 4x4 and welcome to the Dentside brethren.
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It does have bigger tires but I understand these weren't build for speed I will just cruise at 60-65.
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Fleet Mechanic
Joined: Jun 2011
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From: Southern California
Did you look to see if it has headers? My truck 1974 F250 screams at 70!
My 79 bronco is loud but you can hear the radio over it very easily without turning it up high.
Cranky Old Guy
Joined: Mar 2008
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From: Raphine, Virginia
Here is one of the best calculators I've come across. Drop down menu's for tranny's, transfer case and ability to compare any changes you might think about side by side. A cheap SunPro tach and you can keep your engine in it's powerband for best mileage.
Gear Ratio Calculator
Gear Ratio Calculator
Senior User
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From: Chesapeake Va.
keep this in mind though, the higher the RPM's the faster you are gonna beat the viscosity out of your oil. So if you do intend to do a lot of high speed interstate running and this truck is geared low you will be doing more oil changes.
I'm not familiar with the T-18 and can only assume that it is a "granny four speed" so its not like its a four speed being fourth is an overdrive so with that your fourth/final gear is like normal drive and highway speeds are gonna sound like you are tached up real high. But again I dont know if a T-18 is a granny or not.
Look into a taller tire, if and when you need tires, and you will drop some RPMs
I'm not familiar with the T-18 and can only assume that it is a "granny four speed" so its not like its a four speed being fourth is an overdrive so with that your fourth/final gear is like normal drive and highway speeds are gonna sound like you are tached up real high. But again I dont know if a T-18 is a granny or not.
Look into a taller tire, if and when you need tires, and you will drop some RPMs
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