Better prorgam to use .
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Looking for advice on gear ratios
- Thread starter Timmy2tone
- Start date
Better prorgam to use .
Thx.
@Timmy2tone
always match back to same rpm and then go 1 ratio more to help cover the bigger / heavy tires i was always told . and you having a overdrive go DEEP . sbc rpm window is 2k-3k easy all day i would shoot for low to mid 2k at 70mph .
always match back to same rpm and then go 1 ratio more to help cover the bigger / heavy tires i was always told . and you having a overdrive go DEEP . sbc rpm window is 2k-3k easy all day i would shoot for low to mid 2k at 70mph .
Sounds like some great advice. Thanks
Agree, I’d shoot for 2600 ish at 70 mph
Deeper gears help the life of the transmission too. I’d say the 4.56 was a great recommendation for your setup. If you’re planning on bigger tires go deeper.
I have 5.13’s and was right at 2k at 70mph with 37’s. Currently on 40’s and never use overdrive anymore.
I have 5.13’s and was right at 2k at 70mph with 37’s. Currently on 40’s and never use overdrive anymore.
It looks like the 4.56 is what most are recommending. Using the Ratio Calculator Chart it's showing 2145 RPM's at 70 MPH
These numbers don't add up. What are you using for a tach? 1000RPM at 60MPH (0.70 OD) is a 2.38:1 ring and pinion. ("A little lazy" would be an understatement!) With a 3.42 gear, you should be over 1400RPM. And this thread is just like the many other gear ratio threads on here. The basic advice is that with OD you don't regret deep gears.
I'm going to take it out later today. I'm sure I messed that up. How much of a
rpm drop should I experience when the torque conv. locks up? 4.56 or 4.88?
Usually by now someone will say you shouldn't put money into a rear 10-bolt axle because it's going to blow up eventually and ones with tall gears are hard to even give away. Do you have RPO code G80? Any other plans to have a locker or limited slip? Maybe you'll want 37's someday? So the general suggestions in order of increasing complexity would be:
- Find a rear end that already has the gears you want and pick it up cheap.
- Upgrade the axle while you're in there with a new differential and chromoly axle shafts.
- Swap the axle for a 9.5" 14B. Search the tech info thread and see all the options to make this work in 6-lug.
- Admit that you will continue to modify, get bigger tires, etc. and make the jump to 8-lug now, with either the 9.5" or 10.5" 14B rear axle. Front axle just needs the outer hubs swapped to go 8-lug (or find a matching set of axles and swap them both).
The torque converter locking should drop you 100-200RPM, but it depends on the load. Often it locks as soon as it grabs 4th gear, so you might not notice any additional drop. The easiest way to check is to keep the throttle steady at cruise and then engage the brake pedal just enough to unlock the converter.
What are your plans for the truck and how you are going to use it?
The 10B doesn't have much pinion to ring gear tooth engagement when you get into the lower ratios because of the size of the ring gear. Which is why in post #2 I said that my personal preference would be a 14SF six lug. NOT that you can't put 4:88 gears into a 10B, but often times the low gears aren't as durable in a 10B.
A 4:56 set in a 10B may be slightly more durable than 4:88, but it may not be a concern for you.
If you are going to wheel it some and upgrade more later, then it may be better to look into an axle with bigger ring gear.
If you are going to stick with the 35" tires on the wheels that you already have, and don't use it extremely hard off road, then you should be good with a rebuilt 10B.
BUT!!! Don't stick with a G80, (govloc) if you have one! They break easily in the 10B and usually are very tired by now anyway.
I think the extent of my wheeling will be on the beach in the Outer Banks, NC. . Driven probably weekends in the Summer, nothing hardcore. So knowing that do you think changing out the carrier and upgrading axles will work well with a 4.56?
While the unfortunate can happen with trucks and using them, I would go that route if I was limited in axle selection for whatever reason. (Say if I couldn't find the right one to build and swap, or no access to welder)
The original axles in these usually go for over 100K miles before a significant failure. My '90 had 268K on it when it dropped a pinion tooth. It pulled a small trailer around the west with the PO, went and ran a couple of trails in Moab, and a bunch of daily driving. The date code proved originality IMO.
I would rebuild, upgrade some and enjoy.
I would highly recommend getting a Truetrac. I have had mine in very wet snow, powder, ice, Moab, dragstrip and daily driving. My son loved how his Dmax improved with one, so he put one in his 2wd C1500 too.
Don't forget that there will be quite a few extra parts that will need replaced once you open up the axles. Wheel bearings, seals and such. Maybe wheel studs.
Thanks for the advice. I was just on Facebook Market and ran across a GM 14 bolt SF 6 lug. Do you by chance know the distance center to center of the leaf spring perches? Also would the width be the same. The axle I found came out of a '90 Silverado.
Also I'm kind of fond of my 32 yo Alcoa's I bought a year after I purchased the Blazer in 1990. I'd really like to keep them. I guess the bolt pattern is 6x5.5 ?
I don't remember the spacing of the spring pads. But the semi- float 14 was only found in the 6 lug variety in the IFS GMT400 trucks. The spring pads are set wider than your Blazer.
And there are two different widths of the 14SF. The 2wd and 4wd trucks had different widths at the wheel mounting flange. The 4wd one is 67", if I remember correctly. If you use it, then the rear axle is slightly wider than the front axle. Looks better to some, (I like it)
but is not the best for turning radius. I never noticed a difference.
I am. Bought it in '90, drove her daily until I purchased a new Tahoe in '06. In '08 sold her to my buddy that helped me install the 4" lift, wheels and tires and chrome rollbar. He had it for a couple of years before it was stolen from him but was recovered 2 weeks later. Fast forward 11 yrs. my son wanted the truck, Joe had so many other projects going on that he sold the truck back to me for $2500.00So are you the original owner???
Here's our collection of 14B s/f information: https://ck5.com/forums/threads/14sf-tech-info.135125/
