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cheaperrooter
Body Lift
Posts:152
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| 12/28/2006 3:43 PM |
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| I have a 1991 Chevy k 1500 (4x4). It has a 4.3 6 cyl with a 5 speed overdrive. The door label says p225/75R16. I bought the truck with p265/75r16. The truck is pretty much a dog. 1st gear has a problem turing these things. And 5 overdrive is a joke. In order to get any power at all, regardless of my speed, it pretty much needs to stay in 4th gear. I am told it is the tires.....way too big. I looked up the original specs, and it says the truck was offered with p245 as a factory option, but doesnt say that if ordered that way, that it came with different gearing in the rear end to accomodate those, or if my truck will handle up to that with the stock or same gearing. 225 are just to small for me, and 235 are too hard to find. Seems 245 are the way to go, but I am afraid I will buy those tires (265 are new and I already have to sell those)and will not be happy with the trucks performance either. I need some real good advice about 245....will this also mess up my gearing and should I go with 225 and be done with it? Any advice is welcome. |
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webby4x4
Forum Admin, Magazine Editor
Rock Star
Posts:2375
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| 12/28/2006 4:52 PM |
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Your truck did in fact have a 265/75R16 option (no guessing here).
Your 265's are roughly equivalent to a 31.5" tire, and your 225's are roughly equivalent to a 29.5" tire. That's not enough of a size difference to make your truck have a problem simply turning the tires in 1st gear... something else is wrong.
So, the big question is this... is this a recent problem, or did this just start happening?
Rick
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Rick Webster
Editor, 4X4REVIEW.COM - A Tork Media, Inc. Publication
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'74 FJ40 Land Cruiser
"Measure once, cut twice" |
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cheaperrooter
Body Lift
Posts:152
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| 12/28/2006 5:37 PM |
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| Thanks Rick for taking your time to help me out. Ok, let me be more specific. I just bought the truck. When I say it has a problem, I mean to say it takes too much butt to move them. There is no mechanical problem with the truck, I promise you. It runs great. But you can just tell the gearing is way off. 1st gear should be somewhat of a granny, its not. Alot of reving and clutching to get moving in dirt in first. Highway, not a problem. But again, even on highway, you can just tell its too much. In 4x4, of course, not a problem. Lets do real life. I park in the dirt. When I back out of my driveway, slight incline, I am reving and clutching to get moving. Once I hit pavement, 1st gear is doable, so is second. Problem really comes with 3 -5. As I say, gear 5, hell, I can be doing 65mph, and start to actually level out there with it floored. Downshift to 4th, I can punch it and get up to whatever I want. To make this more simple, there are just "GAPS" in my gearing. Always feels like its not a smooth transition from one gear to another as far as relevant to the way it should be. If this was a play truck, I could care less. But I am moving to the mountains where its going to get pretty slick going uphill on some pretty bad roads. I do not need to be going uphill with big tires burning my clutch up just trying to move these babies. So let me simplify this question if I can. Will putting 245 on this truck bring my gearing back closer to the way my gears were designed. Also, you did not say if the gearing in the axle was the same with the 265 option you spoke off. I have heard over and over over the years that putting big tires on a truck overworks the tranny, axle, clutch, etc, etc. IF you disagree, I would love the input. |
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webby4x4
Forum Admin, Magazine Editor
Rock Star
Posts:2375
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| 12/28/2006 6:21 PM |
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I definately do NOT diagree... changing the tire size (increasing it), makes it harder on the drivetrain if the axle gears aren't changed accordingly.
In my mind (assuming that there are absolutely not other problems with the truck), you have two options:
1) Keep the tires and change axle gears (expensive).
2) Change tire sizes back down to a 225.
My gut feeling is telling me that you'll find that the change to 225's isn't going to be enough, and that there is something else wrong, like engine problems, or improper gearing, but again - that's just my gut feeling.
If I were you, I'd check to see what the existing gears are in the axles. You should be able to see this in the glovebox (sticker on the glovebox door), or on the tag that is bolted to the axle. If none of these exist, you can jack up the rear axle and put everything into neutral. Then, make a mark on the driveshaft (lengthwise). Spin a rear tire one full revolution, and count how many times the mark goes by on the driveshaft.
Rick |
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Rick Webster
Editor, 4X4REVIEW.COM - A Tork Media, Inc. Publication
- - - - - - - - - - - - - - - - - - - - -
'74 FJ40 Land Cruiser
"Measure once, cut twice" |
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cheaperrooter
Body Lift
Posts:152
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| 12/28/2006 6:37 PM |
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| Rick, I have 3.42 rear axle. I should have mentioned that. Dont know if its posi or not or if it was even offered. I know how to check for that. I am getting the feeling that your "gut" instinct is saying this. These tires are just not big enough to be causing you any "noticable problems". Yes, smaller tires will do better, but I should not notice any REAL difference with these. I have put tires bigger then these on 4x4's my whole life, but I have always had an automatic. Never noticed a thing one way or the other, I have to admit. This is the first 5 speed 4x4 I have owned, so I was shocked myself to feel the diff. This why I was wondering if this is a Manual thing with the gearing having to be more proper then an auto |
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cheaperrooter
Body Lift
Posts:152
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SnoMan
Lift & Lockers
Posts:943
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| 12/29/2006 3:50 AM |
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quote:
Originally posted by cheaperrooter
Rick, I have 3.42 rear axle. I should have mentioned that. Dont know if its posi or not or if it was even offered. I know how to check for that. I am getting the feeling that your "gut" instinct is saying this. These tires are just not big enough to be causing you any "noticable problems". Yes, smaller tires will do better, but I should not notice any REAL difference with these. I have put tires bigger then these on 4x4's my whole life, but I have always had an automatic. Never noticed a thing one way or the other, I have to admit. This is the first 5 speed 4x4 I have owned, so I was shocked myself to feel the diff. This why I was wondering if this is a Manual thing with the gearing having to be more proper then an auto
Here lies your "problem" I would have never tried 265's with a 3.42 gear stick or automatic. A 3.42 in a full sized truck with 0D is pretty tall even with stock tires. There is a lot of misconceptions out there as to what the proper axle ratio really should be in that some tend to believe the the taller the axle the better the MPG but this is not true because you reach a point where it labors the engine and uses even more fuel. Honestly this truck should have had at least 3.73 gears in it with 4wd and a 4.3 with a manual and stock tires and for 265's it should have at least a 4.10 with that drive train combo. You have the misfourtune to have one of the trucks that GM dumped on dealers with a tall axle ratio to help fleet MPG averages for EPA test on dyno not for use in real world though. YOu options are few here. Go back to a 225 or even a 215 to recover some lost performance or regear axles to 4.10. (even if you swap in a V8 the gearing is really to tall) A automatic would mask it some by riding the stall on converter longer and hunting gears all the time. Granted it is expensive to regear but it would make truck a lot more pleasant to drive and feel like it had a engine transplant and MPG will likely improve as well because it is laboring right now trying to cruise in OD and at beast you have a 4 speed truck right now with a 5th gear that is basically useless. |
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webby4x4
Forum Admin, Magazine Editor
Rock Star
Posts:2375
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| 12/29/2006 8:15 AM |
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Ya beat me to the punch snoman! That's exactly what I was going to say.
Cheaperrooter - I want to underscore what SnoMan said: "Granted it is expensive to regear but it would make truck a lot more pleasant to drive and feel like it had a engine transplant and MPG will likely improve...".
He hit the nail right on the head. 3.42:1 gears are overly tall and a travesty. 1988 through 92 (or 93) was a funny set of years for the big three automakers as they were hit with some stringent EPA requirements and since technology hadn't caught up yet, they were trying everything to get the numbers they needed (think: air pumps... what a hack!). Anyhow, if you put 4.11's in your axles, you'll immediately think that you just bought a brand new truck, and that 4.3L will feel like a small V8! And... you'll be able to keep your bigger tires. It really is the right thing to do.
Rick |
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Rick Webster
Editor, 4X4REVIEW.COM - A Tork Media, Inc. Publication
- - - - - - - - - - - - - - - - - - - - -
'74 FJ40 Land Cruiser
"Measure once, cut twice" |
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SnoMan
Lift & Lockers
Posts:943
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| 12/29/2006 10:22 AM |
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| Yes as it is geared now it will be turning about 1700 RPM at 65 in OD with 265 and it will not pull it unless you have a strong tail wind. Even 4.10's would only give you about 2100 RPM's at same speed but give you a noticeable increase in power. If you plan to play off road you could even spring for 4.56's as that would only yeild about 2300 RPM's in OD at same speed and give you a really usable OD and a much deeper effective first gear and reverse withless clutch slipping needed and you will think that you installed a granny gear tranny in it. You will also get a better over all crawl ratio too (a increase from about 37 to 1 to 50 to 1) and room to go a bit bigger still with tires later on if you choose. As it stands now in drive/4th you are turning almost 2400 RPM at 65 MPH and even with a 4.56 you will be turning about 100 RPM less than that in OD so it will give you a idea of how OD will pull after a swap to 4.56. Go with 4.56 if you want max potentail in a good compromise and you will really feel the difference too or at least a 4.10 otherwise. If it was my toy I would go for the gold and a 4.56 with that V6 as it will give you about the same or better effective power as a 350 with 3.73's and you will find yourself likely raising the hood more to prove that their is only a V6 under it. I have some 4.56 gears on the shelve for my 2000 K3500 that I plan to install next summer (I need truck now for plowing and cannot take it off line) and I will be using stock type tire sizes like I am now still. I buy a truck for power. When I want best possible MPG I drive a 4cyl car not a hamstringed truck with tall gears that is no longer really a "truck" anymore in my book. |
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