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Top Tech: Diesel Tech Questions

You've Got Questions? We've Got Answers!

Bruce W. Smith
Oct 30, 2017
Photographers: Bruce W. Smith
Swap 700R4 To 4L80E
QUESTION: I have a 1983 Chevrolet Suburban originally fitted with the 6.2 GM diesel engine. A few years ago, I installed a low-mileage 6.5L that I obtained from a storm-damaged truck. The 6.5L engine is great, but the 700R4 transmission has failed twice since the swap. Can a 4L80E transmission, which would be the correct one to go behind a 6.5L, be installed in my Suburban, even though it doesn’t have an ECU? Or, would such a swap be a re-wiring nightmare.
Graham Miller
Via e-mail
ANSWER: No technical drama here. The 700R4 is an 4L60, GM just changed the name in 1993, with the electronically-controlled 4L60E showing up a year later. The 4L80 renamed the TH400 in the same manner, with the 4L80E coming in 1991. Swapping out a 700R4/4L60 for a 4L80E is a common performance upgrade, and several aftermarket companies have easy-to-install, stand-alone computer/harness kits to make the conversion including TCI Automotive (888-776-9824) and GOS Performance (800-620-4467). If you really want to step up the game, another swap to consider is dropping in an Allison 1000. GOS has been doing this for several years and have the parts and trans expertise to slide in an ’06 vintage Allison 1000 (has the input sensor) behind the 6.5L diesel. According to GOS’ Aden McDonnell it’s a transmission swap that’s being done on many military Humvees right now. “We would provide the control system for $1,699, TPS kit $129, and momentary buttons to put on the dash for tow/haul and tap shifting,” says McDonnell. “Then we would need the tail housing from the customer’s Allison for speed sensor modifications. We only support the Ford/Cummins conversion parts, so the customer would have to source a flex plate, and an adaptor for the t-case if it’s a GM 4x4.”
Photo 2/5   |   01 DSLP 180300 2017 F350 Regen
A diesel’s regen cycle depends on many factors. For example, a 2017 6.7L Power Stroke will regen at 667 miles unless soot is built up quicker in the exhaust after-treatment system as a result city-type driving, long periods of idling, or even the addition of taller tires and lift kits. Then the regen cycles can happen at 200-300 miles.

Too Frequent Regens
QUESTION: I’m like many other diesel owners that I know: my new truck goes into regen mode a lot. It’s a 17 F-350 PSD Platinum with a six-inch lift on 38”s. This was my dream truck. Traded a ‘15 KR F-250 for it. I don’t tow or drive long distance. Mostly short trips. Yes, I know this is not good for the regen system. But I have to keep it all in place, so “deleting” isn’t an option. I have an Edge Products monitor, and when the truck gets near a regen I get on the highway, keep it in 5th, and drive all the way through the regen. It always burns down to less than five-percent load, and the soot burns down to nothing. I use Archoil fuel additive every fill up down to the exact recommended amount. I did this on my last Super Duty driving the same way and my regens went from every 200 miles to a little over 400 between cycles. So far my new truck appears to be doing the same. Are these frequent regens normal, and what’s the best way to take care of my new truck in this situation. I have almost 10 guys at work in the same boat, so I know this has to be a common question.
J.P. Coker
Via e-mail
ANSWER: Regeneration cycles vary greatly on diesels, and the frequency of the cycles depends on the way in which the trucks are set up and being used. Your new truck, with the lift and city-type driving, sounds to us like it’s working exactly as it should when it comes to frequency of regenerations—and you are treating it properly when it goes into regen mode.. But to be on the safe side, we reached out to Ford for advice and suggestions that might help owners better understand the regen cycles, but received no comments. So we turned to Kenneth Tripp, owner of Tripp Trucks for his expert opinion. His shop in Rock Hill, North Carolina, specializes in Power Strokes with Ford Certified Master Diesel technicians doing the work. “It wouldn't hurt to take it to the dealership to confirm there are no concerns in the regeneration system. But understand the dealership will tell you that’s how it’s supposed to operate in those conditions and that setup,” says Tripp, who worked at Ford on Power Stroke development for nearly a decade. He says the dealer will inform you of the following: 1) Taller tires play a big part in how many miles are actually being driven between regeneration cycles; 2) The way the truck is driven/used determines how quickly the engine builds up enough soot accumulation to spark a regen cycle, with a city truck using more fuel per mile, which means it accumulates more soot than the truck that sees quite a bit of highway driving; 3) And they will ask how much Biodiesel fuel percentage is being used (the maximum approved percentage is 20-percent.) Tripp says the new Super Duty 6.7Ls will command a regen at 667 miles IF the accumulation of soot since the last completed regeneration has not reached a point where it activates earlier on its own.
Photo 3/5   |   02 DSLP 180300 Cummins Head Swap
Dropping a 24-valve Cummins head on a 12-valve block will improve performance with better flow. But doing so requires swapping in the 24V pistons, injectors and custom injector lines to do it properly. An less costly alternative is to have the 12-valve head professionally ported-and-polished so it flows close to that of the newer generation.

Cummins Head Swap
QUESTION: I have a perfectly good 5.9L 12V Cummins block with a bad head. I was wondering if I could put a 24V head on it without a lot of machine work being done? What other changes would it require?
John Williams
via e-mail
ANSWER: The 24-valve Cummins came about as a way to improve air flow over the earlier 6BT 12-valve design, and the head design definitely is freer breathing. Swapping to the newer head makes sense in that regard. But like most things, mixing parts between models isn’t always that straight-forward or cheap. Several of our sources say if you swap a 24V head onto the 12V you’ll need to also swap to the newer-style pistons. The bowls of the 24V pistons are center-cup to accommodate the different injector angle; the 12-valve Cummins injectors come in from the side of the head, while 24-vlave heads have injectors that go straight down. The two engine’s piston top designs are different to accommodate those angles. The head swap swap will also require custom fuel lines, which are available from several different diesel performance shops specializing in Cummins. One of those is Scheid Diese (765-571-0355), one of the top Cummins hot-rodders in the country. Their machine shop manager, Todd Emmert says,“The conversion should be pretty much plug-and-play. The injector lines and fittings will be different [requiring a custom set], and the 12-valve nozzle spray-angle can be modified to take more advantage of the center-cup bowl on a 24-valve piston, but that’s not necessary to run and drive. All in all, compared to all the [Cummins] mods that we have messed with, this is not that difficult. But it is time consuming.” The other alternative to consider, of course, is getting another 12-valve head and having it re-worked (ported, polished, valve job, etc). A good P&P will flow almost as much CFM as a stock 24V, and the machine work is far less labor intensive or costly than what it’d cost doing the 12V-24V head swap.
“P-Pump” Conversion Tip
QUESTION: The April 2010 issue of Diesel Power has a very good article with photos of a 24-valve Cummins being converted to a "P"-pump. I still have that issue, which is what led me to have the one on my 12V converted. The first VP44 to die on my 2000 Dodge 2500 was just as I was turning into my driveway in Pine, Colorado. Not so lucky on the second one. I was between Casper, Wyoming, and Laramie on Hwy 287 right at dusk. I decided right there that I would have the pump conversion done for reliability if nothing else. In February of 2016 I drove the Dodge to Wild Diesel Performance (wilddiesel.com) in West Haven, Utah, and they completed the work in about three days. They allowed me into their shop where I took photos of the conversion process. It was, in fact, very labor intensive! Not only were the pump and injectors replaced, the cam was changed because the cam drives the "lift" pump. Basically, it’s a 12V setup on a 24V engine. So, what doesn't work after the conversion? The "cruise control" but there is an "APPS" kit for that from "Crazy Carl's Turbo's." The P7100 doesn't answer to the ECM, but mechanical "tuning" is possible. The computer throws a code because it thinks the VP44 has taken a dump and you end up with a continual "check engine light". Easy fix: Cover it with black tape or remove the bulb. On both of my VP pump failures there was absolutely no warning, they both just suddenly quit. There are no "new" VP44 pumps; all are rebuilt or re-manufactured. The problem(s) seem to be in the electronics and the VP44 pumps are susceptible to low fuel pressure (cooling) and voltage spikes. Not so with the P7100. As the techs at Wild Diesel put it, "it’s a million-mile pump"!
Dave Mitchell
via e-mail
ANSWER: Good information, Dave. Thanks for sharing with the rest of our readers.
Wrong Number
We mistakenly swapped phone numbers between Mobile Diesel Service (541-459-8939) and FASS Diesel Fuel Systems (866-769-3747) in an earlier issue. We apologize for the mix up. – The Editors
Photo 4/5   |   Atsg Technical Manual Allison 1000 2000
Photo 5/5   |   04 DSLP 180300 Transfer Case Manuals
Comprehensive shop manuals are a big help when tackling transmission and transfer case rebuilds for the first time. A good source for repair guides is ATSG (Automatic Transmission Service Group), which offers a wide-range of such service manuals/CDs/PDFs for Ford, GM, Chrysler/Dodge and import vehicles.

Repair Manual Source
QUESTION: Could you please tell me where I can find a repair manual for a 47RE and 48RE with schematic of components, and dimensions for interchange of components?
Bill Ivey
via e-mail
ANSWER: One source we turn to for nearly all transmission and transfer case repair manuals is ATSG (Automatic Transmission Service Group). You can find the 46/47/48RE manuals here: https://www.amazon.com/ATSG-46RE-Transmission-Repair-Manual/dp/B012GWGW2E. Finding dimensions for interchanging components is more difficult. You might check out TCI Automotive’s website, which has a cool page http://www.tciauto.com/tc/trans-dim where you click on the automatic transmission you need basic dimensions for and the information instantly appears on the screen. If readers know of other sources for good interchange information related to diesels, let us know and we’ll pass that along.
LB7 Buyer Question
QUESTION: I have a chance to buy a 2003 Chevrolet 2500 Duramax from a friend of the family at what I feel is a great price according to Kelly Blue Book. The truck is one-owner, it’s been well taken care of, has 158K, and was used mostly for towing a travel trailer. It smokes a little and has some minor leaks around the engine. But overall, she’s a beauty. The owner says it’s never had any work done except for the normal service. Are there any “hidden” issues with this truck that might not make it as good a deal as I think it is?
P. Lundstrom Via e-mail
ANSWER: Don’t let looks and mileage be your only guide when buying a diesel, which is what pricing guides tend to weigh far more than mechanical integrity. The 6.6L LB7 is a case in point. The early Duramax (’01-’04) had several of engine-related issues that could be of concern, and you should get a copy of all the truck’s service records, or call a dealer with the VIN to see if warranty work was done with special emphasis on the injectors. The original injectors had a major issue with cracking, causing smoke at idle and fuel getting into the oil. Fixing that issue requires replacing all the injectors with newer style, and many of that era had that done under warranty. If the truck you are looking at still has the original injectors, you very well could be looking at a $3,500-$4,000 bill. Replacing the injectors on an LB7 is very labor intensive (10-12 hours), and a set of reman Bosch ones run about $300 a pop. Burned out glow plugs, glow-plug controllers, and corroded/broken glow-plug connector strips were another common issue. Getting the glow plugs out of the engine’s aluminum heads has posed some real problems, adding to the repair costs. Another area of concern with the LB7 Duramax is the integrity of the head gaskets, with typical failures occurring as they start nearing the 150,000-mile mark. An easy way to see if there is an issue with the head gaskets leaking under compression is to squeeze the upper radiator hose (wear gloves) both when the engine is running and right after it’s shut off. The hose should flex easily in your hand in both cases. If the hose feels like a rock, there’s a head gasket issue. You mentioned a few leaks. Is one of those leaks water that’s coming from behind the fan? The LB7s are notorious for water pump leaks, and getting the pump out is another one of those laborious jobs because the dampner pulley is pressed onto the crankshaft, and that pulley has to be removed to get the water pump out. Lastly, the fuel lines had a tendency to rust out in regions of the country where a lot of salt and calcium chloride is used, requiring replacement, and the fuel filter head (on the engine) is prone to leaking around the primer as the o-rings fail. You should also pay close attention to how much boost the engine makes under full load. It should be in the 20-22 psi range if the truck is stock, 24-26psi with a mild tune. If it doesn’t make that amount of boost, there’s an issue with boost leaking off, which affects spool-up, acceleration and high EGT issues. A low-boost problem could be caused by a leak in the charged-air system, a plugged/stuck EGR valve, bad EGR gasket, or an issue with the turbo itself. We’re not picking on the Duramax; every vehicle, regardless of make or model, has some inherent mechanical weakness that shows up over time. Knowing what those are can really help when it comes to buying that particular vehicle, even if it looks great and appears to be in perfect working order. Just be prudent by asking a few more questions and taking a closer look under the hood before owning the keys.

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