Opinions needed

[special-K]

Yup,I`m askin`for it now.

I`ll be putting a 6" lift on my`72 GMC K2500 as soon as I order brake lines and cables.I have a set of 12.50/35s and a set of 12.50/37s.I really want to run the 37s with my white steel 9.75s and hub caps.The truck has TH350 and 3.54 rears.the plan is to swap in either a 4.0 3/4 set or 1 ton set I have (prolly the 1t).I really don`t want to get into the axle swap at the moment.I want to go over everything,rebuild,and do rear discs on the No-Slip HO52 before installing.I don`t want the truck down very long in good weather and will do the axles/swap this winter.
That leads me to the question I want opinions on...How do you all think it will run with 35s or 37s?i know it will need lower gears to run best.But,do you think I can get by with road driving for the rest of the good weather?I love the power now and I know I`ll lose that.it squeels the 12.50/33s with posi hitting 2nd.I know I`ll lose that even with 4.10s.But,I like this tire size with 4.10s.That`s low enough for me.My last one had a 4spd,so it`s been awhile and I`d like to hear what you guys think.i`d wait or winter but the 33s are aged and keeping me from driving much now.
I realize the 37s will be tight with the 6" springs.I won`t be tearing it up off road (as far as articulation goes) and i`ll most likely use zero rates.i could run the 37s on the 8.25s on it now for better clearance.But,I think the sSRs will look awesome on a 1t set-up with a stockish look.I could wait for a set of 35" SSRs.But...I`M LOSING MY PATIENCE!!!

[tallhoedude]

i had a 77 3/4 ton with 354 gears and 35's for a short while.it was a very mild 355 engine,it wasnt all that bad as far as power on accel,sure it was slow,but liveable for a short time.in the mud 4low was great.

my first tahoe had stock driveline and 373 gears,whan i did the ifs lift i ran 37's.again it was slow,but not so slow it was annoying to drive or caused trans issues.

but hey,thats just my .02

[OldCreek]

Remember, those SSR's run true to size. For example some tire co's list 35" sizes at 34.5ish...the SSR's are listed at 35.4ish. The SSR might be big enough to satisfy you!

[dammitmitchell]

i still had to trim the rears of my fenders with 37's installed..
i also have an 8 inch lift...

35's would be good to start with until you get everything done.

the two inches in tire size make a huuuuge difference...

but good luck

[smokekiki]

I have 35's on my Blazer ,with 3.73 rears. It is a mild 350 with TH350. I like the way it runs,fair power for acceleration,but still a good cruising rpm.
I have a 4" lift,like you said no hard wheeling. I am putting zero rates on it to give a little more lift,and to center the rears. I have BFG tires,the are 34.5" .

[OLDCHEV4X4]

Its gonna eat alot of gas on the way to Line Mt.

[special-K]

Thanks,I asked and so far I have ten cents worth.I figure it will eat more gas rolling in a different range.I hope I have it done for the 7-miler,Randy (for spectating:rolleyes).I`ve run 33s on a Blazer with 3.08s.But,it was a 4spd stick.I`m not worried about a TH350 holding up.It`s more about where it shifts without going into it.i`ll only run the 37s if they don`t rub.they are EZ-Rides,so they flex more.I`ve had Xterrains on 10" wheels barely rub with this set-up.I think the 37s will need to go on the 8.25s.

[special-K]

More opinions...more opinions.I want more opinions!!!

[duallyjams]

Opinion,
1) you only need rear disc if you plan on building a mud truck because they are self cleaning.
2) you do not need 1ton axle unless you are building a rock crawler or a pulling truck.
3)6 inch lift 35inch tires, the truck will look good and still be functional.
4) I would how ever swap out the turbo 350 for a manual 4 speed,no heat issue with the trans and with the 4 speed you can use the same gears in the rears.

[jerry moss]

i ran skyjacker 6inch all spring on one of my 72 3/4 tons with 4:10s, 16.5 x 9.75 american racing alcoa look-a-likes and 35" bfg mud terrains and never touched the sheetmetal - even with a trailer hauling 3 yards of pea gravel( 1 1/2 yards in the truck and 1 1/2 yards in the trailer) up on the ranch where my dad and stepmom lived. i think true 37s would have rubbed with that load.

[special-K]

How about 3.54s with the 35s or 37s?That`s my main question.If the 37s rub I`ll bolt on the 35s.I think the 37s may work on 8.25 rims and zero rates.It`s close enought to try,I think.I am considering a 4spd.I have that combo,too.Originally the 37s and 35s were for my shortbed.But,I`m thinking to end up with the 3.54s,auto,and 4" lift on that truck.This is all the reverse of what I originally planned.I want the `72 to be a tough 1t work truck and the shortbed to be a run about,travel,handy dandy toy.
It`s not about need,it`s about want.I want a`72 K/3500.I have the Dana 60 front axle and an HO52 No-Spin for 4.10s.If I need to do alot of rear brake work I want to go to discs rather than scrounge up the drum parts.It`s easy and prolly about the same money.I like mud and I want to work it.I never got that`87 K/30 I always wanted and a`72 would be cooler yet,in my book.
I`m just wondering if I want to do the lift so I can run the tires I have (it needs tires) for the rest of the good weather or just let the truck set until I have the axles ready over the winter.I really want to do crossover steering,too.I really liked my truck with 4spd,4.10s,and 35s.The way the truck is now it runs out like a car.I think I`ll lose that with larger tires even if I compensate the larger diameter with lower gears with an automatic.

[bad421]

I say run the 37's if thats what you want to run. Heck if they rub just order a set of add a leaf and throw them in. As far as putting a set of 1 tons in it, I'd do it. Of coarse I'm putting 1 tons and a cummins in mine so I may not be the one for you to get advice from? Some 37's would look good on one imo, I'd like to run some but I plan on hooking to the sled and going down the track a little so the 35's will be just fine for me. One more thing I would have to agree with a few of the others, a man. trans is always a little bit more fun on the street.

[special-K]

Yeah,I`m a gear shiftin`fool from way back.So you don`t have to shift my arm.I ordered my fully loaded`92 K3500 with a 5spd and my wife`s`90 Blazer was a 4spd manual.I`m scratch-building a`67 GMC swb 2wd with an M22 and all three of my kids learned on a stick,as well as drove sticks in their first vehicles.Everything my wife drove until the one she left in were manuals.I should have known something was up when she bought a Jeep product with and automatic.
I`d love for this truck to end up with a Cummins,too.I want it to be the`72 GMC work truck I`d order today,if I could.
what would those 3.54s work out to with 25s or 37s?I don`t have that formula.I worked it out and just remember for the 4.10 and 4.56 ratios.I`ve never figured 3.54s.I`m guessing around 3:08s with 35s.

[bad421]

ok, you asked. I don't know what size tires a stock one came with but if they were around a 30" tire than the 35's would be a 3.03:1 and the 37's would be a 2.87:1 . Like I said I can't remember what they came with stock so I figured a 30 would be pretty close.

[justcuz]

If you have a tachometer you can temporarily mount, this may come in handy for you. You can also calculate the increase in tire circumference and the effect it will have on your overall gear ratio. I'd go with the 4.10's myself and if the 37"s fit I may consider 4.56's
I am going to put 4.56's in my 71, but with the 700R4 it will be 3.20 in OD. Probably 31" tires.

[special-K]

Thanks alot.I figure a 7.50-16 (or 235/85) is about 31".All this sounds right.The truck has a tach.I`m definately going with 4.10s.I`m just wondering if I can get by until winter with the rears in it now.I also plan crossover hi-steer once I install the Dana60.I have the lift arm for the Dana 44 and it has new ball joints,drag link,bearings,brakes...I think I`ll go ahead and do the lift and tires for now.The 33s on there now are keeping me from running it much right now.

[justcuz]

I like the formula because you can plug in the speed for highway use, the tire diameter can be plugged in and I calculated the final result for the overdrive by multiplying it by .70. Works out great.

If you cruise at 70 and you have 4.10 gears with 37" tires your RPM's at that speed calculate out to 2606. A little higher than I thought they would be honestly. Overdrive would bring it down to 1824.

35" tires would have you running 2755 at 70 MPH, overdrive would bring it down to 1928.

You sure you don't have availability to a 700R4?

That is why I an doing the 4.56 with the overdrive. Low gears for towing and the overdrive for the highway.

[special-K]

I have a 4L80E with stand alone computer from a`91 3/4t 6.2 diesel Suburban that may end up in there.Right now with the worn 33s and 3.54s I`m at 3 grand in the right lane cruising comfortably.My speedo cable is broken,but it seems like 65 or a bit less,maybe.I usually end up passing a vehicle or a few.I have Flowmasters and they are quiet at 3,000 rpm.so,to me that`s not screaming.
The Suburban that housed the 4L80E was equipped with 4.10s and the one set of 35s I have.It rolled along nice @75 mph.What`s the gearing in 1st?Is it low as the 700r4?
I have alot of options I can do down the road.I just don`t want to tear too deep into it at the moment.I may need the truck while doing work on my`92.The two trucks are all I have on the road and money is tight.So,I can`t bite off more than I can chew.

[bad421]

The 4L80E doesn't have the low first gear the 700R4 does it is only 2.48:1.Hope this helps.

[bad421]

The 4l80e is 2.48:1

[4x4Poet]

Your impatience is forcing the issue.

Most tire stores have decent take-off used 33ish tires for around a hundred or two. I bet you'd spend less that way than forcing things before you're ready.

Normally, I'd say the TH350 won't like 37s with 4.10s, let alone 3.54s, but you live in Maryland, so no serious mountain grades. Coming over the continental divide with that truck sometime?

I think the best auto for you would be a TH400 with the low gear set that adds nearly $1000 and necessitates an overhaul to install them. Then first gear with a tough torque converter would be low enough and the 37s would take care of overdrive. But big bucks to do this. SM465 would tackle all concerns except that the 37s would force you to use the unsynchronized granny gear from standing stops unless you don't care how long the clutch lasts.

4.56s would help, but you'd have to change the D60s' R&P and find an H052 3rd with 4.56s. More $$$.

Pick up some better used tires that can handle the highway and one winter and then take your time? I guess that's an opinion.

[special-K]

Hey thanks for you opinion,Poet.I respect your knowledge and know you know what your talking about.I have a set of 235/85s on Ford wheels I`ve consider tossing on for now (may have to).
We don`t have any serious mountain grades compared to the western mountains.But,I do have to cross the Eastern Continental Divide to get back to see my mom .We have some 6-8% grades that are about 10 miles or so to climb.
I`ve run 37s with built TH350s before and they`ve held up.The one truck did have 4.57s.My last lifted truck had 4.10s,4spd,and 35s that made a nice combination.That`s pretty much what I want to end up with on this truck.It started off fine in 2nd.i`m not crazy about the 37s.I just have them.I never built the truck they were for.they will be more of a novelty and the truck will be built more with 35s in mind.It is driving me crazy having the parts to lift it in my shop.the original springs are very tired.The fronts are no about 1" from the stops.Then,there`s the shocks.The body wobbles and rocks like they aren`t there.I`m not into driving it like this at all.It`s "screaming" for suspension.
I just can`t imagine going from 33s to 35s,or even 37s,will require a full turn different in the gear ratio (3.54 to 4.56).
The truck will be a different truck for sure.Back when I had three 3/4 tons this was the mild car-like one.It hauls ass and runs out like no 4wd I`ve had.With a 4spd it will be a whole different story,as well as larger tires.I drive like I`m in no hurry with that trans...just poke along in my big truck.It`s like this...Pass me if you can get around or enjoy watching a tough old truck roll up the road.
I`ll have my little shortbed 327/M22 2wd to get snappy in.

[duallyjams]

What to do , what to do, OOooo my.
I have a ho52 with 4:56 if need be.
Baby steps, just plan and do what you can complete in a weekend.
Sounds like a reason for a get together to me.

[special-K]

Exactly what I was thinking! I`ll announce a cook out.Bring your favorite tools.I`ll stock up on the hand cleaner,too.
I think I`ll go ahead with the lift as planned.Heck,if it`s too awful with 3.54s I guess I`ll park it and be motivated to go over the axles.I can always snatch the 4.10s out from under the`91 Suburban for an easy swap on another weekend (cookout #2).I know they`re in good shape.Mostly the front axle until I do the Dana60.The HO52 was pulled in good working order to install a 3.73.I got it from Rustbuster.
I know a guy in Silver Springs,MD that would like to have the 3.54s for his panel truck,unless a guy from Deale,MD talks him out of it.I think that guy has been to too many oyster feeds.

[duallyjams]

I'll bring my super BFH.