47RH power/torque limits

[KOG]

How much will a stock 47RH stand and what's the least expensive way to get there? 91.5 160 HP is starting point. I've long ago done the cheap stuff, 3200 rpm spring, fuel screw and timing. Still stock exhaust, turbo, injectors. This is a work truck, don't need lots of smoke (actually would prefer about none) or flashy quarter mile times, just stronger pulling power for heavy towing without any reliability issues. 3.54 axle, have a 96 4.10 available as well. Goodrich 285/75-16 TA KO2 rears on Weld 10" wide wheels, 634 revs per mile = about 2250rpm@60mph in 3rd, 3250 @ 60 in 2nd. I've used 2nd in the past with the stock transmission when towing at just under 26000lbs. Power (probably about 240HP) was very marginal (inadequate) at that load trying to hold 55mph on the hills in N. GA. I'd like to see probably 300+ without spending more than necessary or grenading the new transmission. Normal towing load is a dual tandem 24' gooseneck flatbed (6000lbs) with a Case 580C or Bobcat T870, either of which is about 13,000lbs. Truck can carry 5000lbs on the hitch without overloading axle or tires. But it really needs more power.

 

[cerberusiam]

4.10's with a 33" tire will give you a lot better leverage for the heavy weights. The 3.54 is too high ratio to tow heavy and keep things together. Once you power it up you will run into issues with EGT's and engine temp and need the extra rpm on grades. The 47RH stock in new condition is good for around 550-600 TQ , HP isn't going to have a big impact. It is overmatched at those numbers but it will work with a lower gear ratio. You try to push it too hard with a 3.54 axle and it won't like it, the TC clutch and direct clutch pack will suffer badly.

No reason to run it stock with the cost of shift kits, a $100 investment will net many times that in returns for longevity. Stock TC will be a problem, it won't like the weight and heat. You need a billet TC to handle the power uprate and the weight. The clutch packs with a good rebuild are adequate. Problem is you won't find a good stock 47RH anymore, to old. Anything you get will need rebuilt to be solid. The seals and clutches are just going to need replaced. Depending on mileage and usage the pinions will be the worst wear points. The aluminum cage housings just wore out under heavy usage.

 

[KOG]

This is the fresh rebuild that I just swapped so condition "should" be good. And again, I don't want to throw tons of money at this thing. Shift kit, yes. So, what's the least expensive way to get to 550 ft lbs? Exhaust is about a certainty, probably more turbo but no need to go overboard, and a mild injector upgrade should get there. But what shift kit, exhaust, turbo and injectors?

 

[Simplysmn]

I have a good friend that build's Transmission's and we are getting ready to do a 47rh swap into my crewcab .He doesn't believe in shift kit's say's a diesel does not need it . You can turn the Line pressure up and have a good solid torque converter and do the same thing . as for Power if you are still running basic stock set/up I would do this first. either find a HX35 or even a super B turbo . and also Look into a set of Newer injector's such as 5x12 or 5x13's .Best bet is contact ERIC @ thehungrydiesel.com he's a really good first gen guy and will guide you in the right Direction without a ton of useless Smoke .

 

[KOG]

I have a good friend that build's Transmission's and we are getting ready to do a 47rh swap into my crewcab .He doesn't believe in shift kit's say's a diesel does not need it . You can turn the Line pressure up and have a good solid torque converter and do the same thing . as for Power if you are still running basic stock set/up I would do this first. either find a HX35 or even a super B turbo . and also Look into a set of Newer injector's such as 5x12 or 5x13's .Best bet is contact ERIC @ thehungrydiesel.com he's a really good first gen guy and will guide you in the right Direction without a ton of useless Smoke .

Will do...

 

[cerberusiam]

550 ft\lbs is easy, just turn the pump up a bit. The stock injectors and pump are easily capable of 200-220 HP which will get that much TQ. You start running out of injector and turbo in the 250 HP range but that is still enough for 600 ft\lbs albeit a bit warm if you push it to hard. Bolt on parts an it is easily 320\800 ft\lbs. If you want clean usable power then it will cost some $$. A set of DDP injectors and a S300 series turbo, a 60 mm compressor with 67-68 turbine wheel in a relatively tight housing will be needed to spool it well enough to launch heavy loads. It won't make the big numbers up top but that is not where you run the engine anyway, that 200-2500 rpm range is the target for a tow rig.

For towing you will want as low of gears as you can and adjust road speed with tire size. A lower stall, not too low or it will be a dog, and higher efficiency TC will make all the difference. The lockup is there for final drive so the fluid coupling doesn't need to be so tight.

If one is just doing minimum power upgrades and running a light load the stock configuration can work with some tweaks, but, not anywhere near adequate for real towing. There is a limit the stock pressures can be raised with changing springs on the PR and TV valves, there is a limit to apply volume that can be routes to clutch packs with drilling out orifices and plate ports. Once you do that it is a shift kit anyway you cut it, the stock setup was barely adequate for the stock derated power levels and lower weight ratings, it won't hold raising either. A 47RH is nothing more than a 46RH with a lockup TC, it is anemic in pressure and clutch counts where it matters. The idea that a diesel trans does not need help is simply a faulty opinion, can be nothing more considering the body of evidence. Short yourself on the trans and it will be the weak point.

 

[KOG]

So far, cerberusiam has provided to most useful information. As noted in the beginning, it's already been turned up at the pump, 3200rpm spring, timing advance,been that way for several years. I'd estimate no more than 240HP based on empty acceleration numbers. It survived with the 46RH through careful management of temperature and running it in second gear to reduce torque load on converter and clutches when heavily loaded. Also limited speed to 55mph when heavily loaded which cuts the aero load from a backhoe or Bobcat sticking up on the deck of the gooseneck trailer. Hasn't had a heavy load on the 47 yet, but temperature control is as expected, far better than the 46 with moderate loads. I expect engine temp to be significantly better in hot weather as well due to far less heat going into radiator from transmission. The deeper pan on the 47 also contributes to temp control, but not nearly as much as the lockup.

Any recommendations for a specific shift kit? Given that the 47 is really no stronger than the 46 I've already got a problem unless it's modified. I've already got the kickdown cable set for slightly higher than stock shift speeds to raise line pressure a little. Looking into the 4.10 swap. The 96 axle appears to be not quite identical, but close enough to swap. I know the stock steel wheels do not interchange between 91 and 96 (yep, I've tried it), but the Weld Racing aluminum ones on the rear should according to their info. Reducing tire rolling radius is a non starter because of the load capacity required. There are no smaller diameter tires which can carry the 3750lb load per tire.

 

[cerberusiam]

Fairbanks has a kit that works pretty well, TransGo should have one also as should Superior. They are all pretty much the same, you get springs to raise the line pressures and instructions to drill ports to raise the volume delivery. Pretty sure on those the rear support needs drilled to allow more fluid to the OD pinion as all the 618's need. That is a bit more involved as is drilling the input shaft to better cool the direct clutch pack, need to know where and how large to be effective.

Word of warning on the shift kits, if the VB is not good and tight and the manual valve not in tight spec you run the risk of smoking the forward clutch pack when trying to get fluid circulation in park using a different manual valve. Not all manual valves are created equally and not all VB's are tight to spec. Safest way is still put it in neutral for 30-50 seconds before taking off.

If you did not use a better flex plate that is a weak point. A 2nd gen plate with a billet cover TC that has a lot of surface area to clamp the plate to works pretty well. PATC has a 4 mil plate that is twice as heavy as stock and will still flex if you need to purchase one. A stock TC with the stamped cover and lugs is really weak especially if you are towing heavy. All the power has to go thru it and when they heat up the cover flexes causing slippage and more heat which puts more stress on the flex plate and bolts. The lugs do not have enough surface clamping area to handle the TQ, once you go over about 500 ft\lbs it becomes a problem.

Leverage thru the gears and tires will also accelerate problems, it might pull with 3.55's but it will pull a lot easier with 4.10's and allow more use of lockup. Much less stress with deep gears and tall tires than short gears and short tires, that hits the weak spots of the flex plate, TC, and the direct clutch pack the hardest. Judicious use of lockup, gears, and speed extend the lifetime but we really want to be able to run as fast as possible at any time instead slowing traffic.

Lockup will definitely help engine and trans temps, if you can hold it. Nice thing about having switches is you can modify the VB to make sure you can lock the TC in any gear and adjust for extremes. You can even engage OD in 2nd gear to manipulated ratios a bit. Still would highly recommend an aux cooler activated by thermostat for times when you have to use fluid coupling.