Gear vendor's with 3:54 rear gears and th400?

[davischevy]

WE purchased a GV for the 454/400, 3.73 gears, 72 Suburban my son in law is building.

I'm anxious to see how it works.

[chewychevy67]

Originally Posted by jocko

I am strongly leaning toward a GV behind my K20 for similar reasons - would prefer to keep the motor and t-case in the stock location, but the tradeoff is more $. GV behind an NP205 is around $3K, whereas a stout 700R4 could be a little less. Unless, of course, I forget and leave it engaged when in 4WD, then it just got a LOT more expensive . Anyway, it's personal preference.

My gut reaction was same as kwmech, i.e. 3.54 might lug the motor if in O/D below 55 mph or so. It's easier to see the impact by looking at cruising rpm rather than final drive ratio. Here's a comparison with a 30" tire of your current configuration, adding a GV, and a GV with 3.73s. ~100 rpm less at 55 mph (i.e. the 3.54 with GV vs 3.73 with GV comparison) might not sound like much, but when it's ~100 rpm less from 1790 rpm, you start to get in that gray area where you might lug the engine at lower highway speeds.

To be honest, a 3.54 is a pretty user friendly highway gear - a GV price is a fairly high one to pay when you're not already revving to the moon at 65 mph anyway. But I do understand - I want one pretty bad too (but I have 4.10s )

Also, to your comment about being sluggish in lower gears - it won't have any effect. 1st, 2nd, 3rd final drives all remain the same and you simply add a 4th o/d gear - unless you use it as a gear splitter to insert the .78 after each speed (i.e. operate as a 6 speed) - but even that doesn't affect your 'from a dead stop' performance, 1st is still 2.48 x 3.54 for a final drive of 8.78.

i cant figure out the math to do this. any chance you could do one of these rpm charts for 4:10 and 3:92 gears with the gear vendors?

[Heavymetl]

The 700R4 gear ratio spread is poor as well. The big drop in rpm going from 1 to 2 is brutal.

Gear vendors is an amazing product. They shift firm, quick, and they are quiet. Not a single bit of noise cruising or under load. If you can't run a 4L80E (first choice for me) then a TH350/400 and Gear Vendors is the way to go in my opinion.

[bbrriiaann1973]

Cost?

[chewychevy67]

I don't want this to turn into a cost v's 700r4 thread guys. There are plenty of those. I will never put one in my trucks. I am simply wanting info on gear ratios and the gv Overdrive and pros and cons of adding one. Thanks.

[jbarron]

Ive got one behind a TH400 and 402BBC. But that is with 4:10 gears.
If I had 3:54s I would not add a GV, it would be too much reduction.
If your thinking about fuel economy it will never work out.
With the GV on you are driving another gear set and it becomes a wash.
With 4:10s on the highway running 4500rpm was a little much.
The GV reduced it closer to 3500 and I'm happy with that.

Run the 3:54s and if you don't like them swap them for something else.
I think you will be happy with them.
The cost of the drive shaft mods alone will just about pay for a new gear set.

[chewychevy67]

I am going to change my gears at this point I believe. I am going to add the gear vendors but you are correct 3.54 is too low. I'm building this truck to have fun in so fuel mileage isn't really a major concern. I like that I can get my rpms down and have it be a bit quieter in the cab and save my engine some wear on the highway. I'm just debating between 3.73, 3.92, or 4.10s. Would liven up the bottom end and give me a little on the top. My engine is an 275-300 hp 327 stock but will be rebuilt to same specs as stock.