anyone running 35" tires w/4:10 gears?

[cochino12]

I got a pretty good deal on some 4:10 gears for my DD but think they might not be enough gear for 35" tires 700r tranny. Anyone running this setup? what do you think of it? I was planning on 4:88 or 4:56 gears.

[2wdBlazer]

I think 4:10 is about standard for 35's with no Overdrive. I would go with the 4:56 with a 700R4.

[Mudder]

I run 35's with 4.10's............@70 mph I'm running about 2700 rpm's.

[super-k]

With 35s on 4.10 rears comes out to right about 3.73 on a 3/4t that would have originally had 7.50x16s(235/85x16),or about 31"dia.If you go to 4.56s w/35s,you`ll end up with about 4.10s(4.09).What`s your tire diameter now?

[Grim Reaper]

4.10s with a no OD tranny is about right but with the 700R4 I would go with a 4.56 for sure on the low end. I would concider 4.88 but not much more. Pinion gets small and as heavy as these trucks are it starts running hot and wearing fast plus it's easier to snap.

[LONGHAIR]

I confused.........why are you guys recommending a lower gear for the overdrives? The 700r4 has a lower 1st gear than the non-OD (th350/th400) already and then you are giving away the advantage of the overdrive with a lower final drive ratio.

If you are concerned that 4.10 is marginal as far as standing start acceleration with a non-OD trans, then the lower 1st gear of the 700r4 should compensate for that. Plus you gain the highway overdrive. If you go too low in the rear you don't get much use of 1st gear. It shifts out too fast and the overdrive becomes no different (RPM wise) than your non-OD trans would have been with the higher gear.

Pinion head diameter is not the weak point.......they are all using the same size bearing. The weak point is the area where the pinion head meets the inner bearing. There is actually less leverage applied to that area with a smaller diameter pinion head.

[JIMs70GMC]

I have 4.10s and 35s in my GMC seems to be a good balance.

[CrazyCooter]

Originally Posted by LONGHAIR

I confused.........why are you guys recommending a lower gear for the overdrives? The 700r4 has a lower 1st gear than the non-OD (th350/th400) already and then you are giving away the advantage of the overdrive with a lower final drive ratio.

I was thinking the same thing.

I've been running 4.10's and 35's w/ TH350 for 10 years. I tow heavy loads GCVW exceeding 13,000lbs, and only wish I was lower geared when driving offroad. I would love to have overdrive for those longer trips when iIm unloaded and a lower 1st to get out of the hole quicker.

[jamesjones]

Originally Posted by CrazyCooter

I've been running 4.10's and 35's w/ TH350 for 10 years.

TH350 is the big difference. If you're not running an overdrive tranny 4.10's are probably the best balance of economy and power.

The problem with larger tires and a 700R and larger tires, is that you can’t seem to get enough RPM’s to get the OD to properly engage. 4.88's or 5.13's would be a great choice for a 700r and 35's depending on the power production of your motor.

Assuming a true tire dimension of 35”, a vehicle with a small block motor mated to a 700R and 5.13's would spin 2241 RPM’s. Running with 4.88’s would have the engine humming along at 2132 RPM’s, only saving 109 revolutions of the motor per minute at 65mph. Most small block motors are comfortable running between 1800 and 2800 RPM’s. 5.13’s or 4.88's with the addition of OD allow this number to be on the lower end of the spectrum, while allowing for maximum acceleration and off road performance. Anything less than 5.13's or 4.88's w/35" tires will will have your tranny jumping in and out of OD when cruising along at freeway speeds.

[1FaastC10]

Originally Posted by LONGHAIR

I confused.........why are you guys recommending a lower gear for the overdrives?

simple. to hold the trans together. 700R4s are weak if you havent heard.

[LONGHAIR]

The 4.10 with a 34" diameter tire ( your 35's are not really 35" tall) should run about 1850 RPM at 65MPH. That should be plenty for it to stay in OD and really help your mileage. Plus you get the advantage of a 12.55-1 first gear final drive ratio versus the 350s 10.33-1. The non OD (350-400) trans will run nearly 2800 at the same 65 MPH.

Nothing was ever mentioned about strength. As long as the motor is fairly stock I don't see a problem...... 700r4s are not that bad.

[cochino12]

Lots of info and opinions here thanks. I guess I am more concerned about the thing not being a complete turd getting on the highway or getting up I-70 than I am with gas mileage. Motor is basicly stock with a mild cam, nothing crazy. I think I will have to just sell the 4:10s and get me some 4:56, I would hate to spend the money on install and not have enough gear.

[CHEVYJEFF]

got 4.10 and 35's and it does good on the highway and good in town. this is with an overdrive

[jamesjones]

cochino12 my brother in law has an 88 K5 with 35" MTR's, TBI 350, 700r4 and 4.56's and when I talked to him about regearing my 72 he told me 4.56's were ok but he wished he would have gone w/ 4.88's for the reasons I stated above. I had a chance to ride in it a month ago and I agree. Unless you can get a screaming deal on 4.56's I'd go with 4.88's but that's just my opinion. I'd hate for you to spend all of that cash to regear and then not be satisfied with the result.

[beeroh]

35" Muds w/ 4.56 Gears w/ 700R4 and my tranny jumps in and out of OD on the highway. My engine must be weak or my gears aren't big enough

[1FaastC10]

another advantage of the lower gears is that it puts the engine within its powerband, where say you were running 2.73s with 44s, sure your cruise rpm would be awesome (948 rpms in OD) on paper, but when you start putting a load on the engine, such as maintaining speed, the engine lugs. when lugging the engine isnt going to be very fuel efficent.

[LONGHAIR]

You've highly exaggerated this...............

The point was that 1850 @65 MPH should be fine and give you a pretty good all-around drive. Lower 1st gear to get rolling, Not too high in 3rd for towing, Good MPG in OD on the highway.

[1FaastC10]

yes, it was exaggerated a bit, but it proved a point. personally, i like to spin mine to around 2000+ @ 65. i'm looking into 4.56s for my truck.

[LONGHAIR]

The only point that it proves is that you get lower milage running 300/500 RPM more at 65MPH. I drive a mid 90s Dually at work (Company truck) several days a week. It runs somewhere between 1800-1900 RPM and has no trouble at all staying in OD. I pull a 14ft enclosed trailer with it like that most of the time too.

The actual gear ratio required for a given RPM depends entirely upon the tire's diameter. (NOT the crap printed on the side of it) Tire daimeter is affected by the wheel width too. It is actually better measured as the radius.

beeroh, it really should stay in OD at 2000RPM, but there may be a mechanical disadvantage to the taller tires affecting this.

[jamesjones]

The mileage difference between running 1800-1900 RPM's and 2200-2300 will be negligable but the difference will definitely be noticable by the seat of the pants and keeping your engine and trans at a healthy RPM.

I bet that dually you drive at work is a big block. That's a completely different story. I think everybody knows that a 35 BFG isn't actually 35" it's no big secret.

[1FaastC10]

Originally Posted by LONGHAIR

The actual gear ratio required for a given RPM depends entirely upon the tire's diameter. (NOT the crap printed on the side of it) Tire daimeter is affected by the wheel width too. It is actually better measured as the radius.

YOU'VE GOT TO BE KIDDING ME! YOU CANT BE SERIOUS!

[LONGHAIR]

I wouldn't bet that "everybody knows", mainly becasue I'm sure that they don't. It is just like anything else..........taken litterally by some.

Not the truck is not a big block, typical 350.

I'm totally serious about tire diameter being affected by wheel width.
Test it yourself. Once you get to the 33-35 range (and above) you will see a measureable difference in tire diameter by putting the same tire on an 8", 10" or 12" wheel. The odd thing is that it does the opposite of what most people would think. The wider wheel makes the tire taller.

None of the calculations are absolute though because of the growth of the tire at road speed.

[Bobalouie]

I look at it this way...newer trucks, like my dads 2003 Z71 are cruising about 2200 rpms at 80 on the highway using a 4L60E (same gear ratios as the 700R4) and a 3.73 rear end. The tires are P265 70 R16s (31.7 in tall, call it a 32). A theoretical gear ratio/speed calculator says that the rpms with that combo should be 2193 rpms, so the calculator is pretty accurate. If you want to cruise about 2200 rpms at 80 using 35s and an OD trans, you will need a 4.10 gear. The calculator says that you would be turning 2204 rpms. That puts the same strains/stresses on the transmission/drivetrain as a current model truck. You dont the the extra umph off road as a lower gear, but you get better economy everywhere else. And if you need a little lower gearing for some offroad work, drop the T-case into low.

[jamesjones]

Theoretically you would be right but a majority of people cruise around at around 70 and your engine/trans will be much happier turning 2200 rpms at 70 w/ 4.88's than the 1900 it would with 4.10's. It also says something that you can order your dads truck from the factory w/ 4.10's, I guess the factory planned on people putting 35's on thier truck. Like I said, I've ridden in and driven several 4x4's with 35's and 4.56's and from my experience (and the owners) they all needed more gear.

[Bobalouie]

The Z71 package only comes one way, with a 3.73 gear. You cant get a 4.10 from the factory. I guess it all comes down to powerband. Where your engine makes its torque. If your engine is making the majority of its torque at 2000-2500 rpms, then 1900 rpms isnt lugging the engine.

BTW I am not trying to come off as a jerk here, but I am getting ready to run 35s on my truck and was going to regear to 4.10's. It is a pretty expensive mistake to make if it is not enough gear, which is why I am trying to argue my point. If my logic is flawed, then I want to know it now, not after I put new gears in my truck.