3.08 to 3.73

[mk3barti]

That is pricey. Took the truck in for gears and posi this morning and the shop told me I could get a built 700r4 for less than that. He actually half convinced me to do it, but I want to see what things are like with the current transmission before making that decision.

[KQQL IT]

I like my gears at the race track 3:82 with a 3500 stall but... sure enjoyed driving it a bunch more with 3:08 and a 2500 stall...

[MTCK]

I think you'll like the gears. It's amazing what a little more mechanical advantage does for getting these heavy trucks moving. Around town it will be great and spinning a few more revs on the highway won't hurt anything. My old 77 K10 had 3.08's originally with an sm465, swapped to 4.10's and loved it. On the highway I did a lot of commuting at 65-75 and if you're tuned right they really don't mind. Both my current trucks have 4.56's in the axles with 32 and 33 inch tires. No OD and 32's limit how fast I'll drive the one, but the 4L80E and 4.56 with 33" tires are a great combo. Let us know how it drives.

[Firebirdjones]

Originally Posted by MikeB

Yeah, those numbers are pretty close to what the calculators show for your combo. I'm surprised you don't see more RPM due to slip of the 3600 T/C. ??? I would have guessed another 300 RPM at least. I have found that cruising along on a level highway, my stock T/C slips 100 RPM or so. More under load; none when coasting.

It depends on the converter used. Cheapy converters aren't really that efficient. I run a custom built 10" Continental, they couple very nice and under normal driving they aren't all that loose. If you flash it however it'll jump to about 3600 or so. Excellent converters.

[Firebirdjones]

Originally Posted by mk3barti

That is pricey. Took the truck in for gears and posi this morning and the shop told me I could get a built 700r4 for less than that. He actually half convinced me to do it, but I want to see what things are like with the current transmission before making that decision.

Depends on what you want out of it. I see better than the 20% mentioned with the swaps I do here, and they aren't $4,000 either.
I buy them for $2695 brand new, then have the driveshaft made local for about $250-$300 and you're done. If someone is paying $4k for a rebuilt unit someone is getting taken to the bank.

However, the old 700 is probably the cheapest route you could go. Not all that popular among the muscle car crowd I deal with anymore though. Gear spread isn't favorable, and it takes some coin to beef one to take abuse. I've generally spent about $15-$1800, and on up to about $2500 on good quality rebuilt 700's that will take some HP. So in the end if I want strength and durability out of it, I'm not saving much.
4L60's 80's, and now the 6L's have become all the rage for auto overdrive fanatics. Again they are pricey and in the end you'll spend more than a gear vendor going this route. You need $600+ controllers to run them, but some of the models are much stronger to start with. I'm doing more of these swaps for retro applications now. No TV cables to mess with, stronger transmissions, and complete control over trans variables at the touch of your fingertips.

It's just one of those scenarios, damned if you do damned if you don't.

I will say this however, since we are talking about trucks. Most of us tow with them. Even with a 700r4 you aren't towing anything in overdrive, so you're still buzzing down the road in 3rd gear with a load.
A gear vendor on the other hand doesn't care, and that's one big advantage with them. That's one reason they are popular in trucks/towing applications. Rated at 2500HP they are virtually bullet proof, perfect for towing and knocking rpm down a few hundred on the highway is nice.
The other advantage here is gear splitting around town when towing. Really helps when towing to get up to speed, a little easier on the engine too. They are actually pretty sweet when used to their full potential in a vehicle like this.

[slotard]

Originally Posted by tucsonjwt

The Gear Vendors website says that a gv unit will only improve fuel economy on a non-lockup torque converter vehicle. Modern lockup transmissions will not experience better fuel economy, but will have additional gears for improved towing, etc. My 83 C20 454 granny 4 spd with 4.10 rear axle has a gear vendor and it went from 9/11 mpg to 11/13 mpg after I had the gear vendor hooked up, which is the 20% fuel economy improvement that GV advertises. I would not get a GV just for fuel economy because they are very expensive to install (like $3-4K even for a rebuilt unit.)

I don't see why it'd work on a manual but not lockup auto, driving down the highway they're very similar. The gearing you have will matter though, if you're already at 1800rpm at 70 it won't help but a lockup 350 with 4.10s and 30s I imagine it would help.

[mk3barti]

New gears and posi are in and wow what a difference. Truck feels a lot more responsive and doesn't feel like it has to wind up. Off the line pulls a lot harder and two lines of rubber looks much better than one. Highway is 3300 rpm at 65mph and is not nearly as bad as I expected. Very happy that I went this direction. Appreciate everyone's input and help with this!

[MTCK]

Awesome. Glad it worked out.