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| Re: Power Drive [message #327205 is a reply to message #327191] |
Sun, 17 December 2017 10:02   |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma:
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Senior Member |
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NGG,
Welcome to the group, family, cult, asylum....
Education of new owners is something we make a serious issue of here. All of us here have been witness to enough mistakes to make for a massive experience base.
You are largely correct about the powerdrive being a less than optimum solution, and if the TH425 were a weaker beast, it would be. It was a much better solution than GM came up with 3 years too late. The stock 3.07 was chosen because it was all that GM had. It was actually for the towing package for the Oldsmobile Toronado. It is not that bad if you have a light 23' and cruise at 70+. That was the plan in 1973 and that died fast with the first Arab Oil Embargo (that really made only political complications) and the 55MPH national speed limit. The fact is that the only torque that can be transmitted through the transmission is what it takes to accelerate and move the vehicle. So, the powerdrive cannot vastly effect that transmitted torque.
How tough is a TH425? Lots of owners have put Cadillac 500s on them and have no more trouble than the rest of us. Then there is Jim Kanomata (Applied GMC => put them in your speed dial) that has a twin turbo 540 and the only thing that he does not break all the time is the transmission. So, don't sweat that one.
GMs recommended solution was the 3.41. That is just enough to keep the carburetor out of power enrichment is most cases. But for my money (I am only a couple of kinds of engineer and worked in as with automotive for decades) the 3.55 is a better choice. I know you are looking at 2700 at 60, but do not try to relate this to a modern much lighter vehicle. That is just wrong in so many ways. Our coach with a 3.07 is running a 19~2100 at ~60MPH, and the intake depression (vacuum) is disturbingly low and this is with a 9600# coach.
So, for the near term, leave it alone. Learn to drive and maintain her and enjoy what she brings you. If you are going to make the change to EFI, you are in the right place. There are many here with very successful installations. This forum can be searched and so can both GMCMI and GMCWS for more information. When you have learned enough to frame a question, come back here for the right answer. We have people writing here with literally millions of miles and many decades of experience. Me? Yeah, I'm a ship's engineer by training and other things, but I have only had a GMC for 12 years and 70K, that makes me young in this group. Yes, I write long answers, but they are simply because most serious questions cannot be covered with a simple answer. I don't mind as I am trying real hard to pass along what many very patient people have taken the time to teach me.
There are other GMC Motorhome places on the web. There are multiple on FaceBook, but technical answers there should be checked as I have seen several occasions of wrong and dangerous answers. That does not mean stay away. It a great social forum. There is also a group at RVillage.com. I know, I started it and so far it has little value.
Before too long, do us all a favor. You are running the forum, so, go to <Control Panel/Account Settings> and scroll down to the place that you can fill in a sigfile. Please put in a real name (so when other GMCers meet you, they will know who you are), Short about the coach (you did say 76 Glenbrook in the first, but some E-mail readers only see one post at a time) and a geographic reference (the header the e-mail readers never see does say Washington) but try to be a little specific and I will tell you why later. This will be a help to both you and us, and again there is a reason. Remember to scroll down to <Update> when you are done.
You bought a coach and found your way here, that is good, but what you may not realize is that the coach is more than just a new big toy because it connects you to this community. You are now part of a community like very few others. It is filled with helping and supportive people that really do want you to enjoy both the coach and what she can bring to you. To this end, they can do just amazing things. If you hang around here, you will get to read some incredible but very real stories. The only other community like this that I know of is that of the watermen that are my world. For that reason, I have taken to welcoming new owners here much as any new owner or vessel would be welcomed there. So,
May the Good Lord bless this coach and all those that set forth within her.
Welcome Vadim
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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