Truck is embarassingly slow

[TJSc20]

I have a 72 C20 w/ a 350. since I bought it i have opened up the exhaust a little and put a quadrajet on it. The people who had it before me put a turbo 350 in it, i do not know what the rear end is. I assume 4:10, but it is geared very low. I run out of gear at about 60mph. I am getting about 9mpg which i assume is the powervalve on the quadrajet, but yesterday while checking my 0-60 time it was 17s! And the truck topped out at about 78 after a good 30 seconds of hammering it! Could this be my gearing causing all of this? I have a 3spd manual w/ a granny gear I am considering putting in it, but unless this has any substantial gain to offer i do not want to waste my time on this truck. Being geared so low I would have thought it's acceleration would be great, but it sucks. Another thing I was considering was a new torque converter. A few months ago when i put a new turbo 350 in it my torque converter i got with it smelled burned up, then when i got it together it whined real bad for about 2 weeks and then it quit whining. Now it slips here and there when i take off at a stop sign, I probably should have switched that out a long time ago but i didnt think anything of it. So, if anybody has any suggestions on what to do to my truck please let me know.

[Longhorn Man]

your trans sounds like it is about to crap out on you. Assuming the level is good, then it will be going sooner rather than later. The burned smell you described also points to an experation date rapidly aproaching.
Your trans may be slipping bad enough to be hurting our 0 to 60 time, you could have a worn out motor, and you may be expecting too much out of a heavy nonaerodynamic truck.
I've neverr driven one of these with an old stock 350 and felt it was fast by any means.
I doubt your gearing his holding you back on 0 to 60. It'll hold you back on the top end, but it should be able to hit 100 with no problem regardless of engine or tranny options. The fact that you are maxed out at 78 MPH tells me you are either running a worn motor/slipping tranny... or, more likely, you are afraid to run it past 3800 RPM.

[treveiger]

I have a 307/sm465 with a 4.56 rear end im pretty sure and its not fast but it will get up and go when i want it to. Sounds like you need a new tranny, id say go with a manual but if you want to hammer on it all the time and jam through the grears id get a m22(i think thats what the camaros had in them im sure somebody will corect me if im wrong) instead of your granny tranny you want to put in it because there ment more for racing and the shift ratios are a lot better for your 0 to 60 time.

[68gmsee]

I wonder if they converted from a manual to auto or six to v8. I did that on my old 69 with a 4.10 and had a similar problem with it reving extremely high at highway speeds. It had plenty of power on the takeoff but sounded like it was going to explode in the higher speeds.

I changed to a 3.08 and it solved my problem. MPG was about 15 on the highway and 10-13 in town.

[BIGBLU 72]

M21 or M20 would be alot cheaper to comeby and MAJORLY LESS ANNOYING than a M22. 700r4 is the way that i would go!

[todd99]

I have the same setup as you and my truck runs like a raped ape. The 4.10 gears should make it faster, not slower (up to about 120mph). I don't know if it is your tranny, but something is seriously wrong. I would start with the simple stuff before jumping to the transmission, fuel filter, pump, timing, bad valve. Have you checked your compression?

[special-K]

My 3/4t 4wd with 350/TH350,3.54s,and 12.50/33 tires,and posi catches 2nd when I floor it off the line. If it ad 4.10s it would even be quicker and catch 2nd more. I had a 2wd 3/4t as described above except 4.10s and another 4wd the same way and both were quicker. I'd run 75-80 down the interstate,too. I love that sound.

[treveiger]

Originally Posted by BIGBLU 72

M21 or M20 would be alot cheaper to comeby and MAJORLY LESS ANNOYING than a M22. 700r4 is the way that i would go!

I knew it was a M something that would be good and work, whats the difference between the three?
Thanks

[BIGBLU 72]

M20 has a deep first gear (wide ratio) M21 and M22 have the same gear ratios but the M22 has straight cut gears and that causes them to whine unbearably! all M22s are also fine spline and take the same yoke as a th400. late model M21s (70-74) share the same fine spline shafts too!

[wwotr]

Originally Posted by 68gmsee

I wonder if they converted from a manual to auto or six to v8. I did that on my old 69 with a 4.10 and had a similar problem with it reving extremely high at highway speeds. It had plenty of power on the takeoff but sounded like it was going to explode in the higher speeds.

I changed to a 3.08 and it solved my problem. MPG was about 15 on the highway and 10-13 in town.

I did the same thing with my 67.
It had 3:73 gears, that would spin the tires with a stock 350.
After I went to a 3:08 gearing, it was embarrasingly slow.
A SLUG to be exact.

[maynardtruckin]

Plain and simple you have 4.56 or 5.13 gears. the power valve sounds fine and if the trans was on its way out the fuel mileage would would be far worse, like 5 or 6 mpg. I have a 70 half ton with 3.08 gears and when the trany went south I got about 6 or 7 mpg. if you get bigger tires or change the rear end gears it will get better but right now you could pull your house off its foundation!

[maynardtruckin]

Originally Posted by todd99

I have the same setup as you and my truck runs like a raped ape. The 4.10 gears should make it faster, not slower (up to about 120mph). I don't know if it is your tranny, but something is seriously wrong. I would start with the simple stuff before jumping to the transmission, fuel filter, pump, timing, bad valve. Have you checked your compression?

Only faster out of the hole! 4.10's are good 1/8th mile gears depending on tire size. and with the stock 350 and a th350 and 3.73 gears I changed to i got about 140 and when i went to the 700r4 i got 145 and one hell of a ticket.

[todd99]

True, 4.10 is a little too much. My truck will almost never use first gear.

[Longhorn Man]

fast does not equal quick
quick does not equal fast
Fast is a high MPH
Quick is the amount of time to get to said MPH
A 3.07 gear will be faster than a 4.10 gear all other variables being equal.
a 4.10 gear will be quicker than the 3.07 gear, again, all other variables being equal.

[gonzo6869]

Originally Posted by Longhorn Man

fast does not equal quick
quick does not equal fast
Fast is a high MPH
Quick is the amount of time to get to said MPH
A 3.07 gear will be faster than a 4.10 gear all other variables being equal.
a 4.10 gear will be quicker than the 3.07 gear, again, all other variables being equal.

Well said and if you want the best of both, get yourself an OD Trans with 3.73's in your rear.

[Jacfourteen]

I agree with longhorn man about quick vs fast. That said your 4.10's should be great for 0-60 runs, if your in the 17's to get to 60 you have a problem. You need to hit all the basics before you jump into swapping trannys (although yours does sound like its not in the greatest shape).

[doctrouble]

I've also heard somewhere, maybe even here, dunno been a while but thought it was am amusing. "Rpm is how fast you hit the wall, Torque is how far you make the wall move" i might have butchered that

[todd99]

3.07 for velocity
4.10 for acceleration

so whats the best gear for jerk force?
...thats not an insult, jerk is a unit of measure.
....it is the measure of force that throws your head into the rear window when you hit the gas.

[brad_man_72]

jerk force sounds alot like centrifugal force and the easter bunny. No such thing. Your head isn't being thrown back when you hit the gas, the truck is accelerating, pushing your body foreward and since a body at rest stays at rest uuntil acted upon by an outside force it feels like your head is being thrown back but in reality your head wants to continue to stay going the same speed.

so the QUICKER the truck accelerates the more force the trucks seat applies to your body pushing it foreward..... Unless you're in reverse when hitting the gas.

[LedSled71]

[Longhorn Man]

yep.

[68gmsee]

Originally Posted by wwotr

I did the same thing with my 67.
It had 3:73 gears, that would spin the tires with a stock 350.
After I went to a 3:08 gearing, it was embarrasingly slow.
A SLUG to be exact.

Well,,, at my age the old tire spinning, drag racing days are way gone. I did that back in the late 50's and early 60's. I was mainly looking at mpg's.

Surprisingly enough, I had no problems with lack of power and for my purpose, which was farm work, it was fine. I towed a MF135 tractor with a 6 foot bushhog and a boxblade all in an 18' trailer for 150 miles and it towed really well.

[tim21391]

on my 402 when i had problems with it "falling on its face" like it did the exact thing... my secondaries wernt opening up on my 4 barrel.. so i fixed that.. then came to find out my points were shot.. so i replaced it with an autozone accel hei distributor, coil, plugs and wires and it fixed the problem

[Ironangel]

Sounds like to me youve got a truck that needs alot of corrective tuning! I would drain and inspect all the fluids from the crankcase to the rearend! Take a look at the modulator valve and its vacuum supply. Inspect and change the plugs(spark) that will tell volumes of info on engine health and carb tune. You indicated "opening the exhaust" a bit, how? Ill bet it was quicker with a bbl on it. Ill bet that Q-Jet is either dumping more fuel into the ol girl than she can handle or that its so far out of tune that a draft nags going to out run it no matter what the trans and ratios are. Raise the rear axle and count the rotations of the drive shaft to one full turn of the wheel to get your rearend ratio. Slightly over 3 turns is 3:08, slightly over 4-1/2 turns is 4:56. Me? Id stick with 350turbo(if its still good)and changing fluid and filters in them tranny's with a new modulator valve works wonders,(if) the fluid indicates a somewhat healthy tranny.

[todd99]

http://en.wikipedia.org/wiki/Jerk_(physics)

The derivative of velocity is acceleration, the derivative of acceleration is jerk, physics 101.