1970 Blazer Granny Gear
 

Hello, I'm new to the site, and glad to be here.
I have a manual 4 speed transmission in my Blazer. I am familiar with the "Granny Gear", being 1st gear, but I never use it unless I'm just using it to move a little bit forward, or teaching my daughter how to drive a manual shift. The only other time I have used the granny gear was in a 1967 C-10 wrecker and in that situation, I used it a lot. On my Blazer, I can let the clutch out at an idle and it will crawl along as one would expect, but I can't get any speed without winding out the 350. I have had other 4 speeds with the granny gear, and I do what everyone else does by starting out in 2nd gear, but then it wants a lot of RPMs to get going and is winding out at 60 mph. The clutch is in perfect condition for now, but if I have to give it more RPMs to get going, I'm probably going to burn out the clutch before long. The 2 gallons to the mile thing isn't all that great either. I wanted to get some input on if I should change out the gear ratio, or look into putting in another transmission. i'm only running the equivalent of 33 inch tires, and I don't know what the gear ratio is now, but it seems pretty high. (The higher the ratio, the lower it is geared) I would like to take this vehicle on road trips without burning up the motor, and drive it around town without burning out the clutch.

Thanks for any help you can offer. I hope I did this right!! Thanks again!

Re: 1970 Blazer Granny Gear
 

You're not going to burn out the clutch by driving it unless it is not grabbing and slipping while driving. As far as the ratio, the K5 should have a 3.08 I believe. All the K5s I owned had that ratio with the factory 28'' tires. 33'' tires with the 3.08 should drive really nice. A lot of guys shoot for that final drive when installing a 5 speed or an automatic with OD

Re: 1970 Blazer Granny Gear
 

Thanks for the reply KWMech,
I just got this Blazer, and I've seen some fairly, let's say, different things that have been done to it, so I don't know what gear it has. I will get that figured out. Great body, motor, frame and price! I'm putting it back together and I'm putting on the finish coat, so it's all good for now. Like I said, in 1st I can let the clutch out at an idle and it will slowly chug along, but when I'm pulling out into traffic, as normal using 2nd, it takes a lot of RPMs and clutch to get it going. The clutch is very strong, but in 4th at 60 to 65 the motor is running really high RPMs. It's Red Drum Season on the Outer Banks, and I guess I will just take the back roads and enjoy the ride at a better pace. Thanks again for your reply. I will get some pics and more info posted when I get used to this site.


It's the Journey almost as much as the Destination.

C

Re: 1970 Blazer Granny Gear
 

The SM465 has always been a "truck" transmission...with the K/5 it's low 1st gear is ideal for off-road, slow maneuvering and also for holding back on the downhill trek.
If you don't go off-road then your best option would be to swap in an overdrive manual like the NV4500....and re-gear to a 3.73 ratio
some of the NV4500s still retain a low first gear but have the overdrive as well.
It sounds like you have a low gear already if it's turning fairly high RPM at 60-65 MPH

The only problem is that this would be an expensive swap.
You could also swap to an overdrive automatic....also an expensive swap unless you found a donor vehicle...cheap.
Both will require a fairly involved amount of labor....

Re: 1970 Blazer Granny Gear
 

Thanks for the reply,

Ultimately I want to swap out just the transmission to an automatic, and then see how that works, but it's fine for now. I see that you are in East Tennessee. I have a place in Tellico Plains TN. It is 7 hours away from where I live, and mostly interstate. I have a new Tahoe that I have been taking up there, but I would love to one day start taking the K5 and hit the trails. Getting up to the Outer Banks for surf fishing isn't too bad, since there is no interstate from here to there, but that's where the lower gear would come in handy.

Thanks again! Great looking Blazer on your post!

Re: 1970 Blazer Granny Gear
 

Upper Tellico OHV Park was the best Off Road Riding East of the Mississippi River until the tree huggers and trout fisherman managed to get it closed to OHV activity....
Many local clubs, in conjunction with the Southern 4WD Association worked diligently to keep it open....ultimately, the squeaky wheel got the grease, and it was closed permanently.
I'm about 45 minutes from Tellico Plains....I spent many days up in the mountains riding the infamous trails of the OHV
"Slick Rock" "School Bus" "Guardrail" "Lower 2" "Helicopter Pad" all bring back some great memories.

A picture from "Guardrail" at the "Dixie Run" in 2006
Attachment 2064488

Re: 1970 Blazer Granny Gear
 

Let's get some actual numbers going on here...

-What RPM are you hitting on the highway at 65MPH?
-What size are your tires?
-Can you jack up the rear end, put the trans in neutral and spin the tires 1 revolution and count how many times your driveshaft spins? (Or spin the driveshaft X times to count 1 tire revolution) Then we'll know what gear you have.

I don't have a manual in my K5 but my '65 F100 has a granny gear (6.5:1 ratio) 4 speed and I start in second gear like you but it does not need all much RPM to get going. It doesn't have an over drive so in 4th (1:1) it pulls around 2500 at 65MPH. The truck has 37" tires and 4.10 gearing, though.

If you do swap in an automatic i'd recommend you get an overdrive trans or the high rpms on the highway will remain the same.

Re: 1970 Blazer Granny Gear
 

That's next on the list.

When I first got this K5 I drove it around town enough to figure out what needed to be done. Since then I have torn down the body and hope to get the finish coat on today.

I'm running 285/75R16s so they are 32 inches from the ground up. It didn't come with a tach in the cluster, but there is a space for one. I'm going to hook up a temp tach until I get one for the cluster, but for now I can hear that the RPMs are high enough in 4th at 60-65 that I don't want to push it any more than that. Once I get done with the body resto, I will jack it up and find out the gearing. When I do swap out the tranny, I will put in an overdrive. A friend of mine who I did some work for is giving me a complete running 2008 Tahoe LTZ (4X4) with the 5.3L motor, and overdrive tranny, so I will see what I can do with that.

I have lots of other things that I will be posting about, so more to come, and thanks for the help!!

Re: 1970 Blazer Granny Gear
 

2008 is not the best for conversion. Not saying it's bad, it's just the 08 has displacement on demand and it uses an ECM and a TCM unlike the older engines (07 classic and older) with just a PCM controlling the engine and transmission. If you're going to use the 08, I would change out the lifters and disable the displacement on demand and run an aftermarket computer.
FWIW, 2002 is the best donor IMHO because it's the last year for drive by cable. 2003-up uses drive by wire which works fine, but gives you a horrible pedal feel which can't be changed using the factory computer.

Re: 1970 Blazer Granny Gear
 

Another issue with that DOD motor can be excessive oil consumption after it gets some miles on it.
I had an 07 Tahoe that had it...drank oil like crazy...finally traded it off

I just bought a 2000 Tahoe pullout....complete with engine, trans, and transfer case for $1200..it was still in the vehicle and I was able to see it running.

Re: 1970 Blazer Granny Gear
 

Sorry for the long silence, but I keep finding other things that need attention as I go along. According to the tags on both differentials, I have 3.07:1 gears. I made sure by marking the tires and the drive shafts, and they were pretty much spot on. I'm not going to change the gears or granny tranny yet. I have some other things that I will start a new thread with, but I just wanted to thank ya'll for your responses and input.

C.