slow hi boy
Senior User
Joined: May 2004
Posts: 185
Likes: 0
From: Bedford Hts, Oh
I'll go for that. I am in 3rd by 25mph. I run high RPM's on the highway. It will shut down on me if I get to 60. Stall speed?
I've thought about getting an auxiliary transmission or lift it and larger tires. The wife says she wouldn't be able to drive it, so she x'd the lift idea.
Last resort, changing gears.
I've thought about getting an auxiliary transmission or lift it and larger tires. The wife says she wouldn't be able to drive it, so she x'd the lift idea.
Last resort, changing gears.
Laughing Gas
Joined: Aug 2004
Posts: 1,138
Likes: 0
From: Yuba City, Ca
my 78 F-250 with 4.10 can do 85@4200rpm if you got 4.56's you should be able to run at 70 thats only 3500rpm's with stock tire size. now if you up the diameter (6") to 35's you can get another 10mph with the same rpm's. 33's(4in bigger) would let it run about 6mph faster at same rpm's. get my drift. now if you went 12" bigger which would be 40's you could run about 22 mph faster. Pretty cool.
o yeah the reason for the no power at high speeds is cause all the torque for the 351M/400's is about 3000rpm. Not to sure bout the FE's though. probably the same though.
-Aaron
Please use the edit function to add to a post rather than posting again -Admin.
o yeah the reason for the no power at high speeds is cause all the torque for the 351M/400's is about 3000rpm. Not to sure bout the FE's though. probably the same though.
-Aaron
Please use the edit function to add to a post rather than posting again -Admin.
Lead Driver
Joined: Sep 2003
Posts: 5,844
Likes: 5
From: Albuquerque
Originally Posted by 76hi-boy
my 76 ford hi boy with a 360 and a np435 tranny seems to be vey slow and it tops out at around 60 is that normal? any suggestions?
My '76 F150 4x4 390FE with T18 tranny will get up and MOVE. Our trannies are pretty similar, but your 3rd gear is lower than my T18 and thus results with a lower shift point than mine. And mine tops out at 55-60mph.
This is all said not knowing what axle gear ratio you are running. If lower than 3.50's, then you should not be shifting from 3rd to 4th at 60mph period. Really need more info...to provide a better answer.
Here are the gear ratio's for the NP435:
NP 435 = 6.69 3.34 1.79 1.00
Hope this helps some...
Last edited by biz4two; Dec 4, 2004 at 12:04 AM.
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Senior User
Joined: Nov 2003
Posts: 173
Likes: 0
Originally Posted by 76hi-boy
my 76 ford hi boy with a 360 and a np435 tranny seems to be vey slow and it tops out at around 60 is that normal? any suggestions?
What size tires are you running? Large tires will decrease your indicated speed, and the increased rolling resistance will make it harder for the truck to turn rpms at speed
Check your timing, exhaust, carb for something that would be restricting power at higher rpms.
Good luck.
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Joe Kucinski
Senior User
Joined: Mar 2003
Posts: 306
Likes: 0
From: Rancho Cucamonga, CA
Originally Posted by f250rangerexplorer
o yeah the reason for the no power at high speeds is cause all the torque for the 351M/400's is about 3000rpm. Not to sure bout the FE's though. probably the same though.
-Aaron
-Aaron
Very true! I think the 360's power range with the stock cam is 1500-2500rpm (or something close)...after that there is little torque to feel the acceleration. In my 73 F250 4x4 with 33" tires and 456 gears, I did around 2800 rpm (or 3000, cant remember)at 60mph. Thats where i could feel the truck stop 'pulling'. I could get it up to 70, but it takes a long time and at those rpms, the engine sounded like it was going to explode because of the rigid fan.
The 360 has alot of low rpm grunt, but feels like it runs out of breath if you run it over 3k. It really out accelerates my 99' F150 4x4 with a 5.4 upto 55.
Freshman User
Joined: Sep 2004
Posts: 30
Likes: 0
Are you sure you don't have the transfer case in low? That sounds ridiculously slow, and I don't mean that sarcastically. On the freeways here, you would be shoved off the road or denied entry if 60 was your top speed. It really sounds to me like you are in low range. Granted I have 3.50 gears, and 33" tires, but I get to 55 and am somewhere around 2200rpm. I don't know how fast my truck will go, but it will easily exceed most speed limits if it were so inclined. Do you have a high ratio rear end, and small tires? Then I guess it could be that. Try some larger tires maybe? I am curious to hear the results of this.
