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Did a search but still need answers...Gearing questions for towing...

T

triger

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<font color="green">Alright this is not for me but for my old man.

He has an '86 K20 3/4 ton pickup.
350 carbed all stock.
700r trans transfer unknown
14bsf and dana 44 8 lug w/ 3.73 gearing.
35 x 16.5 x 12.5 rims and tires. sorry his tires are 33's. mine are 35's... /forums/images/graemlins/blush.gif

Truck cruises ok but lacks the get up and go on hills. He also has a dual axle cargo / camper trailer gvwr 7000lbs.

What will be a good gearing for both trailering and daily driving? He does alot of traveling (1500 miles or so) with trailer. Any help would be appreciated. /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/ears.gif /forums/images/graemlins/thumb.gif

T </font>
 
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and a 454.

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<font color="green">Well if I came across a 454, I sure and hell wouldn't tell him, I would put it in my truck! /forums/images/graemlins/wink.gif But he would love to do that if possible.

I was thinking 4.10's myself but always like to hear others opinions. /forums/images/graemlins/thumb.gif

T </font>
 
i might go with 4:56's seeing how you got the OD an all. but i dont have much expirience with that tranny or towing soooo my Opinion doesnt mean much.
 
With the OD tranny you can go pretty low and still have a good cruising RPM. For example: 35" BFG= 599 Revs per mile + 5.13 + .7:1 OD = 2151 RPM @ 60 MPH. This would take a lot of stress off the transmission and make fourth gear actually useable.
 
I personally would go with 4.88's. I have 4.56's with 35" tires and a 700R4 and wish I had went 4.88 or even 5.13's.
 
Yup yur definatly under geard. Go with at least 4.56.
My Buddy has 4.10s in his K2500/700r4 with 16" tires and it is a little under geared when towing. He had taller 35"? 16 inch tires on it but went back to a 33" 16" tire because it lost too much power in the hills with the tall tire.
 
[ QUOTE ]
With the OD tranny you can go pretty low and still have a good cruising RPM. For example: 35" BFG= 599 Revs per mile + 5.13 + .7:1 OD = 2151 RPM @ 60 MPH. This would take a lot of stress off the transmission and make fourth gear actually useable.

[/ QUOTE ]

Couldn't have said it better myself. /forums/images/graemlins/thumb.gif I have a crew cab with 35" BFG's and I'll be installing 5.13's next month!
 
If he tows alot then 4.10s. If you go to 4.56s you will have high rpms when towing. Dont use od when towing. With 4.56s you will most likely have to use od when towing to kep up with traffic.

Dan
 
I'd have to agree with the 4.10. Not saying you cant go 4.56, but then you'll be in OD most of the time. here's what i found when towing 5400 lbs (tandem 16 foot trailer) unenclosed, so its less wind drag....

31" tires: 3.73- was able to tow in D with ease, but found that cruising at 65 caused excessive engine RPM. found that I can tow flats and slight inclines in OD without engine bogging, or the tranny searching. LArger hills, I would just switch to D, or keep in D and just go at 60. Engine and tranny seemed perfectly happy.

33" same combo- Same drive, but found that I had to switch down to D a lot more. Mild hills required D, instead of OD.

35" same combo- OD was almost useless when towing. However, resulting speed was a few mph off- so while my speedo would say 60, i was really doing 65.


With 35, I would say go 4.10, and if its a big trailer load with a lot of wind resistance, I'd go 4.56.

I should have a smiliar combo- 700r4, 208, 350, the only difference being I have TBI and some header/exhaust. Dont think it should be that dramatic a difference.
 
I've towed a 5000 lb. trailer all over the west and have used 3.73, 4.10's and 4.56's. Have used the T400, NV4500 and a 4L80E trans in various trucks. Nothing works better with 35" tires then 4.56's, especially with a stock 350 carb'd engine. You'll spend very little time in OD while towing except when flatland running, as it should be. When the road starts climbing 3rd/direct will be much better then if you had 3.73 or 4.10's. Plus when you have to shift down in the hills, and you will shift down, running along in 2nd won't seem so slow. My NV4500 has about the same ratios in the top 4 gears as a 700R4 and works very well with 4.56's and 35" tires. 4.88 and 5.13's are great but you could spend too much time in OD and effect the trans cooling too much. OD is really not intended for towing. I used to have a 98 Chev truck with the 454/4L80E 4.10's and it did a fine job, until 35's were put on it. Too many times 3rd was too high and 2nd was too low. I've normally tried to gear for about 42-48mph in 2nd gear at about 3000-3200RPM. Great for trans and engine cooling as well as fuel economy. I think with my present engine/trans combo I could get away with 4.10's much better then your dad's truck could. SBC just don't build the torque that a BBC does.
 
I would suggest that you go with the most gear that you are comfortable with at highway speeds in third gear while towing. Ease the strain on the motor/tranny with the lower gear with the 35's .That 700R4 will not like those trailer weights and towing in O.D. - go for some extra gear but nothing less than 4.56's w/ 35's . JMHO , Tom
 
<font color="green">OOPs my bad...I put my tire size down instead of his...His tires are 33's...Alittle tired last nite when posting... /forums/images/graemlins/blush.gif But it still sounds like most people are pushing for the 4.56's...

T </font>
 
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