Granny Gears Too Low..Solutions ?

[benbloom]

The granny low 4 speed in my 69 k10 is too low for driving on the highway, or any speed over 40 mph. I am looking for a way to be able to go faster at lower rpms, what would be the best way of doing this? Is changing the gear ratio a good idea? or replacing the transition itself? Please give me your input! thanks!

[my67c20]

Welcome to the board and . What rear gears do you currently have? What rear end is in the truck? You have 3 options. Change the transmission, change the rear gears, or get bigger tires. All depends on your budget. So, what is your budget? What is your fabrication / mechanical skill level? Lots of good information from members of this board, so you came to the right place. Hopefully with more info, we can get you a solution. In the meantime do some searching on Gear Vendors, NV4500, overdrive upgrade, and see what others have done.

[hugger6933]

Now just changing the transmission in itself is not gonna help unless you go to a newer type overdrive. Without the overdrive they all end up at the same place 1:1. The gears are probably stupid low but with the K truck you have to change the fronts also so that is a double hit in the wallet. Taller tires will help some but if your geared real low not much gain to be had. To get it to a comfortable place all three may have to be done. I have a one ton that has 5:38 gears and I am thinking a overdrive and a 4:10 rear gear then it will cruise more comfortably. you know there is a lot more riding done in trucks than back then they went to work and gas was also about 75 cents a gallon too. Jim

[kwmech]

Take it out of low range.

[GASoline71]

Take off in "2nd" gear. The "granny low" 4 speeds are basically a 3 speed with low range. I had an SM465 in a 1979 GMC K25 and only used "1st gear" (marked L) when pulling or hauling. I always took off in 2nd gear for normal driving. Which is marked 1st gear.

Cruising at 3,000 to 3,500 RPM's isn't going to hurt anything.

Gary

[special-K]

Originally Posted by benbloom

The granny low 4 speed in my 69 k10 is too low for driving on the highway, or any speed over 40 mph. I am looking for a way to be able to go faster at lower rpms, what would be the best way of doing this? Is changing the gear ratio a good idea? or replacing the transition itself? Please give me your input! thanks!

Change the gear ratio or go with an overdrive transmission. All transmissions will be 1:1 final drive ratio, then there is overdrive. Granny gear refers to 1st gear which is a major reduction gear for getting trucks going when being worked hard and/or for creeping along for certain tasks without riding the clutch
How fast do you want to go? Do you know your gear ratio? I have no problem driving trucks with 4.10 ratio on the hiway. And you don't "have to" drive as fast as the rat race you know. 65-70 will get you there just fine. These trucks have always done what was asked of them, which is the original reason they gained such popularity.

[benbloom]

How do i figure out what gear ratio it has without opening up the differential? i am no mechanic, this is my first truck, got it about a year ago when i was 17. learned a lot since and looking to learn more. i would probably be willing to spend up to 1000$ to fix the problem, but of course less is always ideal. seems like changing the gear ratio might be best, I'm trying to keep it mostly stock, though ive got 31 inch tires on already. this thread is incredible, thanks guys!

[Jurassic-1]

Look on the right axle tube on the rear end there should be some letters. 373=HA 307=HB411=HR,JQorTS

[hugger6933]

Well look in your glove box first and see if a ratio is listed on there. Next there may be a tag on the rear end held on by one of the rear cover bolts if not there may be a code stamped in to the axle tube that is about the only way other than marking the drive shaft and tire then turn the drive shaft and count the turns on thew tire. Drive into driven, IE ten turns on the driveshaft 40 turns on the tire=4:10 of course lots of people do this and turn the drive shaft ONE revolution then count the tire turns,= one driveshaft rev =3 and 3/4 turn of tire =3:73 gears. That is the way most people do the gear search thing.
I'm sure there probably is a you tube tutorial on how to do that rear gear search or something like that so you can know what your dealing with.
Why not find out what you have then post up so we then can discuss your best options then.
Do you have a Tach in the truck to get some kind of idea where the motor is while cruising? It isn't gonna be like the newer truck/cars of recent because of the overdrives that they have . the engine may not be revving or working as hard as you think it may just seem that way.

[kwmech]

In what position is the floor shifter for the t-case?

[benbloom]

Its not in 4 low, I'm talking 4 high being too low. the other shifter has only 2 options-4high and 4low

[special-K]

Yeah, 40 feels like top speed? Like KW has asked, what position is the transfer case shifter in? Is it all the way forward? Pull it all the way back, then push it lightly till you feel it slip into the next position. Either it's you aren't used to trucks with lower gears and no overdrive and everything is cool, or you're in 4LO.

From forward to back it's: 4LO-N-2H-2L....4wd low (makes gearing 2x lower), then neutral (even with transmission in gear it won't move), 2wd high (normal 2wd), and all the way back is 4wd high (same gearing as 2wd but 4wd). Do you have one of the transfer case knobs with no markings? Is that shifter bent towards your leg or is it bent straight back towards the seat? Could you post a picture? How about pics of the truck??

[kwmech]

If it's not in 4lo how do explain only being able to drive only 40 mph. AND what other shifter

[special-K]

The other shifter is the transfer case shifter, right? It has the pattern I explained. Have you found neutral on the transfer case lever? So, what position is the shifter, back or forward?

[benbloom]

its in 2 high, and when i say 40 mph tops i mean at a comfortable cruising speed, go up to 55-60 and the engine is roaring. and yes i have the oil pressure gauge that came stock working, at 55 I'm pretty much maxed out.
i also looked on the rear axle, stamped on the right tube it says 1 2 3 4 5, upside down. does this mean the axle isn't stock?
thanks for bearing with me people, its my first thread. il post pictures when i can

[benbloom]

also now that I've been taking a closer look, it really seems that there are only 3 positions on my transfer case shifter, 2 high, N, and 2 low from forward to back. how do i engage 4x4? in the past I've just locked the hubs for 4x4 use. i am somewhat sure that this is not a related issue, however if anyone feels differently please let me know!

[special-K]

Are you saying your truck is not equipped with lock-out hubs? Just a bolt-on plate with a bulge in the middle? If so, the hubs are always engaged to spin with the axle. The axle will only spin when the driveshaft does which should only happen when the shifter is in 4HI or 4LO. I think you are only feeling one side of neutral and the other. It's a less noticeable feel between 4HI and 2HI right next to each other.

I think you are just not used to a lower geared truck combined with no overdrive. I've seen this before with younger people who came up with newer O/D high geared cars

[Mike C]

Dana axles came with a tag on one of the cover bolts that will tell you the ratio if a PO hasn't removed them. Otherwise if it is something other than stock should be on the SPID. Sounds like you have 4.57 gears most likely. One cure is bigger ties. 35's would help manage that RPM on the road, but requires a lift. You might be able to run a skinny 34" tire withou a lift which almost gets you there.

Otherwise, gear change or OD trans. I like/prefer the granny 4 speed in a truck so would be looking at gears. Great time to do a disc conversion as well.
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[GASoline71]

Originally Posted by special-K

I think you are just not used to a lower geared truck combined with no overdrive. I've seen this before with younger people who came up with newer O/D high geared cars

I'm betting this is it. These trucks can handle cruising at 3,000 to 3,800 RPM's at highway speeds all day long. It's how they were built. Back then gas was .40 cents a gallon no one cared that they would pass everything but a gas station. Small blocks don't start making power until they get a little RPM in them anyways.

Gary

[my67c20]

Always good to see someone that gets the old truck bug when they are young. Better news is there has been a lot of good suggestions posted so far. So on your list, the first thing you need to do is post pictures (exterior, interior, rear differential), check the inside of the glove box, and check the gear ratio as per what hugger6933 suggests. Also what is your budget?

[kwmech]

The roaring could be his fan blade assy, just seems like its screaming, put a tach on it even with 4.56 gearing you should be able to run 55-60 with a small block without major issues

[benbloom]

http://67-72chevytrucks.com/vboard/a...1&d=1435166967


this is my tranny and rear axle, anyone recognize either of them?

[benbloom]

Thanks for the input everybody, the issue is not with the transfer case me thinks, but rather with the nature of the transition and gearing being too low for practical freeway use. i do a fair bit of free way driving, and would like to be able to cruise along with lower rpms. so overdrive or change the gear ratio is what I've narrowed to down too, i like the look of the stock sized tires and want to keep them. so i need to figure out my gear ratio, my back axel says 1 2 3 4 5

[BLT gmc]

The transfer case is a Rockwell. It is a T221. There were several variations '62 to '69. Shift pattern for the 2WD 4HI Neutral 4LO. the 2WD is closest to the firewall, 4LO is closest to the seat. Torque Ranger from Advanced Adaptors is another possiblity for an overdrive with the SM465. Lots of work to do it.

[1972RedNeck]

Jack a tire up, put the tranny in neutral, spin the tire twice and see how many times the driveline turns and report back.