5 speed/o.d. swap comparisons - WC/S10 T5 hybrid, NV4500, A833 MY6, Tremec 3550 Mustang

[Chuck78]

The museum-restored 351C with it's 312ft-lbs torque@1600rpm is having shipping arrangements made to get to me next week. If I find a Magnum top end for it, that will be an extra 40hp (not 20 as I previously stated) & 8 ft-lbs (320ft-lbs @ 1600rpm). The HEI & Holley 500cfm may add a slight bit more power to that (moreso adds response and drivability).
I think a cam regrind with very similar timing but .020" more lift might be the 1st mod I would do if I desire more power out of the 351C/AX15 setup. Honestly the 305D with Holley 500 & HEI has plenty enough pep backed by a 1:1 4sp, 28" tires, & a 3.07 rear, but it's more the hauling torque and low highway rpm capability I'm concerned with. A 351C @ 312ft-lbs & 351E @ 320ft-lbs makes it seem to me that the Magnum top end with it's extra 40hp is less critical for my goals than a larger camshaft lift would be to improving torque output. I keep wondering if a 401M or 432 cam has higher lift specs than a 351 & if it is interchangeable.
I got a random email from a fella I have to write back to, I am guessing from the 67-72chevytrucks.Com or Stovebolt.Com forums. He said he has no problem with his modified 305A pulling a camper trailer after his mods to add 16% hp & 20% more torque. The biggest thing he said he mills the heads .120" (sounds like A LOT! I question intake manifold alignment at that point) to get 9:1 compression, and does a custom cam regrind and adds .020" lift for more of an RV grind profile. I may entertain milling .080" or .090" off the heads if I have them off (or find Magnum heads).

These engines make monster torque just beyond idle, so a 3.07 and a 5spd overdrive 5th turning 1375-1700 @ ~70mph in 5th would be awesome for my road trip drivability. I would like to add a limited-slip carrier to my rear end when I get it rebuilt, so I will then have the option to adjust the gearing to my adjusted preference of highway rpm once I have tested out the ax15 or similar Overdrive. I think the key would be figuring out how low of RPM the engine can go and still make enough power to overcome wind resistance at 70 mph. 312ft-lbs @ 1600rpm is mammoth, so I think one could drop to 1450 on the highway and not have to step into the throttle too hard to maintain that. Being able to slow down to 55mph and still have enough torque output to maintain 5th gear at a low engine RPM may be the actual target I need to focus on in terms of drivability vs a tunnel vision goal of lowest rpm I can efficiently run @ 65mph highway cruising in 5th

[TJ's GMC]

I would keep cruising RPM at a Minimum of 1500. I've noticed with my 305E since I've done the 4 barrel and dual exhaust that 1700-2100 is the sweet spot, and then for highway 2400 is Easily achievable. And that's with 4.11's and a 29-30 inch tire. I'm going to be putting 32's on soon. When under load the engine likes to be at 2000 and maintains very well without having to stomp on it when a grade comes. I'm considering Magnum heads for my 305 and milling them down so I don't Loose any compression. The larger ports, bigger valves, and bigger exhaust manifolds outta gain me a bit of power. And the bore size should be plenty big for that addition. Far as I know All cams from 305 to 478 were the same. You should try Delta Cams and see if they can Make you one. I know they will regrind, but they might produce as well.

[Chuck78]

Good to know. I'll have to play around with both figures in mind, then adjust the rear end gearing if needed when I swap in a limited slip carrier.

[Chuck78]

Alright I had to calculate it for the ax15 and 275/60r15's

Currently, I'm spinning 2580rpm @ 70mph
on 28" tire, 3.07 rear, & standard 4 speed,
achieving a best of 21+mpg on an HEI/Holley 500 305D.

28" tire + 0.79:1 o.d. + 3.07 Dana 44:
1000rpm = 34.35mph
1500rpm = 51.52mph
2000rpm = 68.69mph
2038rpm = 70mph
2500rpm = 85.87mph
3000rpm = 103.04mph
3500rpm = 120.21mph
4000rpm = 137.29mph

28" tire + 0.79:1 o.d. + 3.31 Dana 44:
1000rpm = 31.86mph
1500rpm = 47.78mph
2000rpm = 63.71mph
2197rpm = 70mph
2500rpm = 79.64mph
3000rpm = 95.57mph
3500rpm = 111.50mph
4000rpm = 127.42mph

28" tire + 0.79:1 o.d. + 3.54 Dana 44:
1000rpm = 29.79mph
1500rpm = 44.68mph
2000rpm = 59.57mph
2350rpm = 70mph
2500rpm = 74.47mph
3000rpm = 89.36mph
3500rpm = 104.25mph
4000rpm = 119.14mph


28" tire + 0.79:1 o.d. + 3.73 Dana 44:
1000rpm = 28.27 mph
1500rpm = 42.40 mph
2000rpm = 56.54 mph
2476rpm = 70 mph
2500rpm = 70.67 mph
3000rpm = 84.81 mph
3500rpm = 98.94 mph
4000rpm = 113.08 mph


So my take on that is that the 3.07 would be viable to give me the absolute best 70 mph cruising mileage, but the 3.31 will be better all around & won't require downshifting on big hills or on winding country roads coming out of turns or climbing up hills. The 3.31 really would be more fun to drive at 45 to 65 mph.

The 3.54 (74.47mph@2500rpm) & 3.73 (70.67mph @ 2500rpm) would still be lower rpm's on the highway than a 3.07 + 1:1 top gear transmission (67.83 mph @ 2500 rpm), and would increase the fun factor and hauling capability

[Chuck78]

Certainly a 3.73 rear gear would make it substantially more fun to drive and give it more power towing, but respectable fuel economy on these monstrous gas guzzlers is something I would really like to achieve. If I could get 21mpg highway with a .79 od 5th and a 3.54 rear gear, that would be AWESOME, but I think I may need to need to shoot for the 3.31 in order to achieve my road trip highway fuel mileage goal. I suppose I could inflate the rear tires to the max on long highway drives in order to slightly up the tire diameter!

I will have to consider the added fuel consumption swapping to a 351C over the old 305D when considering gearing, fun/power, & fuel economy.

It appears to be a toss-up between the 3.31 and the 3.54. I feel that with the 3.31/351C/ax15, I can get the same fuel mileage that I currently have with a smaller engine and standard transmission. The 3.54 will certainly be more fun. The ax15 lower gears will make it more fun on top of that compared to my current setup, and I really had no complaints before about the acceleration power without a load.

[Chuck78]

One last important factor to consider when choosing rear-end gear ratios with an overdrive transmission.
The higher numerically the first gear in the transmission is, the more leverage the transmission has on itself to self destruct under heavy load and abuse.
Running a 3.54 Dana 44 gearing behind the ax15 will be a slight bit more forgiving when getting on it when hauling a heavy load, compared to the same condition with a 3.31 differential gearing.

[Chuck78]

AX15 Gear ratios are:
3.83 / 2.33 / 1.44 / 1.00 / 0.79
(1st can be swapped to 4.31 & 5.15, od to .83)
(All gears can be swapped from the g452 Toyota Dyna truck transmission to get:
5.15 / 2.74 / 1.93 / 1.00 / 0.83 // reverse 5.04 / ***Dyna is an international model, unsure of US version)
It weighs approximately 96lbs.

NV4500 Gear ratios from 1995+ are:
5.61 / 3.04 / 1.67 1 / .74 // Reverse 5.61
(93-94 had a 6.34:1 1st & non- synchronized reverse)
It's weight is 195lbs.

There are zero used Dodge gasoline 2wd versions of this on eBay currently. There is one company selling modified remanufactured units at $1,000 plus a $500 core charge, plus shipping.
So you can pretty much plan on this costing you about $1,700 plus the adapter from Novak. $2,000 basically if you want an already modified and rebuilt NV4500. You spend $500 less than a brand-new TKO 500 to get a deep granny gear heavy duty truck transmission basically, $500-700 more for the TKO500 get you a brand new transmission with no adapter and more sporty ratios, and more flexibility in the shifter location.
Certainly you could find a used Dodge gasoline 2wd nv4500 and rebuild & modify it yourself and save at least $500

There's apparently a design flaw with fifth gear in particular, slightly with 4th, and that there is excessive wear on some internal shaft parts. There are several fixes for this problem, and the eBay auction that I reference the price on states that they upgrade several parts internally including a fix for this problem.

[jturk]

Chuck,
To give you an idea of total cost for a 5 speed replacement here's an overview of what it cost me to go to a GM Aisin AR5 5 speed, clutch assembly, driveshaft, throwout bearing, pilot bearing, gear oil, rear end gears, and Novak Adapter.
I spent the following on the different components:
1) AR5 Colorado Transmission - $300
2) LUK Clutch Assembly - $110
3) Driveshaft - $100
4) Hydraulic Throwout bearing - $200
5)Pilot bearing - $10
6) Red Line gear oil - $45
7)Rear End 3.73 Gears - $200
8) Novak GMAX15 Adapter - $325
So if you add all these parts up it comes up to a grand total of $1290.
So all in all the overall expense wasn't bad and the benefits of the 5 speed has definitely been worth the expense especially when you look at the prices of the Tremec or Richmond transmissions.
This is all basically food for thought and have good luck with you decision.

[Chuck78]

Great! Mine will be about $500 less up front, $300 less in the end if I decide to swap 3.31's or 3.54's into the Dana 44. Already have had my flywheel & press.plate resurfaced, gmc clutch remanufactured @ Hite Parts Exchange. Using GMC slave cyl & TO bring / fork, maybe new TO brng
Might buy a new Rhinopac clutch kit while they're still available though just to have it.

As it is now, 3.07 rear end Saginaw 4-speed, even with the 3.07 still, the ax15 will give me much lower highway RPM, a much deeper first gear, and much closer gear spreads after that. With a 3.54 rear end I will really realize a lot more hauling potential, especially behind the 351C. Heck, I probably didn't need to jump on that 351C with this gear combination! I bet it will halt much better even with a 305D + ax15

[Chuck78]

I didn't have enough time to test the 351 and swap the front covers and all before a vintage motorcycle event that I wanted to drive the truck to (in case I bought more bikes or parts at the swap meet!), so I replaced all 4 freeze plugs on the front and backs of the heads on the 305D as it was suspended over the engine bay, and stuffed it back in. She runs great still now that I can keep the coolant in it! Amazing how deteriorated the old steel freeze plugs were. and how stuck the exhaust manifold to downpipe bolts were. I learned that the heat riser was jammed 20% closed on the pass. side also. Fixed that. Torched off the top nuts on the exhaust manifold to downpipe connections, and re-tapped the bolt threads on that side as the bolts just wouldn't come out in the time that I had.

I did not buy an AX15 yet, but I still believe that to be the preferred transmission for my needs and will be looking for one before October. I may do a fair amount of work to the trucks then and into late fall when the garage is still warm enough. Hope to swap the 351C, AX15, and 89 Suburban front disc brake crossmember all at the same time late October. Maybe get to repairing some rusty cab supports and replacing the body mount cushions then as well. Then hibernate in the basement all winter playing with a new to me metal lathe and milling machine and working on motorcycle project builds in the basement until spring! Next year, bodywork on the 82 VW pickup as my first paint job test piece, then bodywork on the GMC and paint on that! Wife says matte black is the only color allowed... Not certain I'm set on that but we'll see.

An A833 MY6 is also something that I'd jump on, but the AX15 is more likely to be found, and an NV4500 just seems like not much gain over an A833 as I won't use the granny gear first much at all and then I'm just left with a very expensive 4 speed that doesn't do much anything that the A833 MY6 wouldn't do.