Weird scenario - power issue with wide-ratio tranny

[Dsilverline]

Hey guys,

I've got a somewhat weird scenario and hoping someone might be able to shine some light on it.

84' CUCV, still have the 6.2 but I've got an SM465 tranny (super wide ratio) and an NP205 Tcase. I also put in a custom injection pump, new injectors, entirely new cooling system, and electric fuel pump, pyrometer, 33's, shocks etc etc

Offroad its great, the crawl gear on the 465 is awesome. With the new custom IP I have plenty of power (fair amount more than stock) in the 1700-3000+ RPM range. The problem is I live in the mountains and there are lot's of crazy hills with sharp turns on the paved roads. For this the 6.2l/465 combo is *horrible*. 1st (technically second gear, not L) is way too low sometimes and 2nd is way too high so I have to drive super slow in 1st till I'm passed the hill and all these people are behind me. If I try to shift to 2nd too soon up the hill the motor bogs down way low and the 6.2 at 1000 rpm has absolutely nothing.

I know if I put in a close ratio 5 speed or something that would be great for the road but then I'd lose one of the best offroad trannys of all time and the crawl ratio(and the primary purpose of the vehicle is road trips to offroad spots). I don't want to put in a Turbo 400 because I really like sticks reliability and efficiency plus they don't have the great crawl gear either.

I thought about a gear vendors under/over as that would solve the wide ratio issue but those even used are mega bucks and the bigger problem as I understand it is that they are not great for lifted vehicles due to the shorter rear driveshaft that is required which causes problems with the increased angle?

If I put in a turbo like the banks I'd get some good mid range power but not much low range as it's a non-wastegate turbo. And where I really need the help is lower rpms right after I up shift. Finding stuff for a GM turbo seems better as that will give me low end grunt to power out of the hole in 2nd coming up the hill.

Possible problem with that is I put on a Nostaglic air kit and the compressor is now hanging off the side of the passenger alternator. I *need* AC as I live in SoCal and go on desert trips. Went two years without it, never again! I'm finishing up the Rosscommon 12v conversion tossing the drivers side alt as it went out the other day anyway. I definitely want easy parts availability.

So I have the two batteries, alternator and compressor all on the passenger side, just power steering on the drivers side - do I even have room to squeeze a turbo in there? I've seen multiple pics, not sure how far forward the banks turbo is. Then again is it too unbalanced having all those accessories and a turbo all on one side?

I guess I could move the passenger alternator to the drivers side, then move over the compressor- jeez seems like just more hassle.

Ideally I don't spend a crapload of money and time on this, if I can get away without a turbo I'd like to - I just need a little bit of extra power to get me out of the hole at 1000rpm due to the wide ratio tranny so driving the mtn roads isn't so annoying.

I wonder if a few small upgrades combined can be just enough - like electric cooling fans + headers and full exhaust? Not sure how to proceed.....

Thanks!

 

[rustystud]

I never heard of a "super wide ratio" SM465 transmission. In fact they have only one standard set of gears for this unit unless some aftermarket manufacture has stepped up and made them. I do remember someone making gear sets for the SM420 but I cannot remember if they ever made them for the SM465. If they did and you have them in your truck then take them out and go back to stock.

 

[Dsilverline]

Didn't mean to be confusing, what I meant was it's a "super wide ratio" compared to say a Turbo 400. I figured most people on here still have that in their rig so just threw that in for anyone who wasn't familiar with the SM465.

Stock ratio as far as I know, still - on some hills I'll be in 2nd (labeled 1st after L) at 3k RPM, up shift and it drops to 1k RPM (installed a tach), then it pretty much just bogs down - crazy RPM drop just makes it tough to drive up here in the mountains with the NA 6.2...

 

[rustystud]

You might have to start driving with the transfer-case in low on these hills then.

 

[quickfarms]

A ranger overdrive will let you split the gears and is only about 7" long.

Sounds like first overdrive would be just the ticket

What tires and gear ratios are you running?

One issue with this combination is the narrow power band of the diesel

 

[Skinny]

I think is more of a gearing selection issue. That transmission is basically a 3 speed for most driving instances. You can only do so much with 3 gears in a manual trans. I agree that a splitter or maybe an NV4500 would do you a lot of good to keep things in the sweet spot.

Even with an M1009, I wouldn't worry about the driveshaft unless you are running a tall lift. You can do many mods here including going to a fixed yoke and CV driveshaft to make it work. Its just money

 

[Dsilverline]

Yes! you guys know what I'm talking about - the narrow power band makes it tough....I didn't even know about the ranger overdrive! First + overdrive would be amazing. I'm looking into that for sure, *way* more affordable than the Gear Vendors. If I get that it'll be hilarious - I already twin-sticked the 205, then I'd have 4 sticks in there haha - running 33" tires, roughly 3" lift and stock axles (3.08 right?)

I took a second look at the gear ratios for the NV4500 -its 1st gear is actually decently low (6.34) although not as low as compared to the SM465 (6.55), seems the jump from 2nd to 3rd isn't as bad as the 465 but still a bit of a jump. Definitely need to think hard about swapping in one of those as well.

Good to know about the driveshaft! Thanks guys, I feel like I'm headed in the right direction now...

 

[kblazer87]

If your truck is the M1009 with the stock axles you found your problem. The 3.08 gears with the 33 inch tires. Up your gears to 3.73s or 4.10s and second gear is your friend again.

 

[Dsilverline]

I actually think the axle gearing is fine for now with the 33s, mainly since I have the spread in the SM465, crawl gear is good and highway RPMs are good. It's just the jump between gears that's the problem. I looked into the Ranger overdrive and I think that's the way to go once I have some scratch to throw at this thing

 

[skysix]

take a look at the GM 2001-2006 3/4 and 1-ton 6 speed close ratio manual (ZF S6-560) Approx 35# heavier than the TH400 at 230# -vs- 195#

1 4.23
2 2.53
3 1.67
4 1.23
5 1.00
6 0.79

R 5.23

 

[rustystud]

I actually like the idea of the "Ranger Overdrive" from High Impact Transmission and Gear. Though it's $1400.00 .