Tonight I spoke with a custom build shop in Georgia about building a one off 4 speed OD transmission for my 77" Airstream Argosy 28 motor coach. It will be based on either a 700R4 or a 4L80E. I am torn between having a shop build it or building it myself. My target is a getting my 3200 RPM cruise down to 2200 RPM. And being back up and running by spring. Probably taking my last camping trip of the year this weekend before I take the AS down for the trans build and EFI/TBI conversion

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Tags: EFI/TBI, RV engines, Transmission rebuild


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Comment by david craft on November 18, 2014 at 8:20pm
Jeff, I'm pretty much in awe of your previous exploits/accomplishments. Pardon me if I seem too proactive as myself and others vicariously build this with you. We all pretty much want to be there im your tolerance has been appreciated!
Comment by jeff york on November 18, 2014 at 5:26pm

David Craft, I have done the math. With my 19.5 inch tires and my 4.56 rear end gears and the final .75 drive ratio of the over drive, I will reduce my cruise RPM from 3200 at 65mph to 2200 RPM at 65mph. I want to stay at 2200 RPM as that's the exact RPM I calculated for the cam grind and the engine build to be at the bottom of the power band range. I don't want to go below that. The hunting was the issue with almost all of the 4 speed OD transmissions and gave mini van in particular the Dodge minis a bad name for trans failure. I had two OD trans failures and learned a lot from those failures and rebuilt those trans myself because I wanted to learn. In fact, one of them blew up and I actually did a complete transmission build by hand.

A few friends tease me a bit for doing projects like this and the 6 year frame off restoration I did for my teenage sons first car. Its not about just paying someone else, its about the fun, the learning and the challenge. I also built my 2 time national award winning racing plane. Built from blueprints and composite layup, engine design and cooling design to instrument panel design and build. Not that it matters but, I have a Mercedes AMG in the garage yet I commonly drive that 15 year old mini van and enjoying my restored nearly 40 year old Airstream which I originally set out to get 10 mpg and beat that with a consistent 12 mpg.

Yes, I may get more than an additional 1 mpg with the trans change. In fact i sort of expect to but keep my sights lower. I achieved what I wanted. So its now just the challenge of doing a 4 speed OD trans and making the engine last longer via turning it 1/3 less and getting ideal A/F air fuel ratios that will add to engine life through less carbon getting into the crank case and breaking down the oil and no hot spotting in the heads from fluctuating A/F as driving conditions change via altitude and load

Comment by david craft on November 18, 2014 at 1:47am
I think you'll gain more than 1 mpg. I was reading 200 to 400 rpm drop on a car. Maybe more I would think on your MH. You mentioned 1000 rpm. I'm assuming you did the math and thats the reduction you get with the lockup, since no gearing changes were noted. Thats substantial. I know when those 700s first come out on the pickups, they would "hunt" a lot during wind loads or hills or light towing, causing premature failure. The idea of a manual switch sounds good to me. You should run cooler during lockup without that torque converter churning extra heat..a nice caveat. I mentioned the michelins earlier because of the research the customer of mine did...a substantial gain as well. I really think your investment will pay great dividends.
Comment by Rich Thomas on November 18, 2014 at 12:41am

This has been one interesting thread Jeff, You certainly have a passion for discovery thanks for sharing it.

Comment by jeff york on November 17, 2014 at 11:43pm

I took no offense to the slight and I say slight deviation from the  4 speed OD conversion to the spark plug indexing. I was not offended and I too got a bit off the track with my comment on plugs but, after all, part of my desire to go 4 speed OD is better fuel econ.

There have been nay sayers and doubters to my claim of now getting 12 mpg in a rig that was getting 6 mpg but, all I can say is, I invite anyone to take a trip with me and see for yourself. I dont really expect to get much better fuel econ with the 4 speed OD but, I may be able to stretch another 1 mpg. Who knows. I said it already and I will say it again, this was not a cheap bolt on solution. It was a significant rethinking and change to the standard rebuild of a GM 454 engine.

I think I have put together the right combination of parts to rebuild my 700R4 / 4l60E transmission to hold up to the weight of my Airstream 28 foot motor home.

I will be focusing on upgrading the Sun gear shell assembly and a stronger sun gear assembly, the planetary gear assembly the drum spline assembly. This should take care of the weaker areas of the 700R4 mechanical assemblies. To combat heat in the clutch assemblies I will be using Raybesto's in combination with Borg Warner clutches. I feel I had very good luck with my TH400 when i put in two large oversize trans coolers and a deep trans pan with cooling tubes running through the trans pan for additional air flow. I will use my two existing remote trans coolers and will add the same type super deep trans pan with integral cooling tubes. I think the cooling and the updated frictions on the clutch plates will take care of any trans temp issues. I am not sure of the Torque converter stall yet but I think a 2500 stall is going to work. I will incorporate the TV cable to my quadrajet carb until I upgrade to a EFI/TBI injection unit. I will also use a switch selectable torque converter lock unless I find a better solution/idea. I will be sourcing my parts from about 3 main suppliers and I think Trutech will be my main supplier for rebuild parts. This is a 30,000 foot over view and I will be extensively documenting my rebuild and my results and tests. It will be several weeks before I gather all the parts and begin. If anyone wants to follow that, I will log that information here. If anyone wants more detailed info, reach out to me and I will be glad to share. I have a lot of details to work out like drive shaft modification and balancing, do I keep the big parking brake drum on the trans output and bolt the drive shaft to the parking brake drum like it is now or will I incorporate a pump up type parking brake or ?? Very anxious to move forward on this.

Comment by david craft on November 17, 2014 at 11:21pm
Thanks Randall for bailing me on this one. This thread has ignited a diverse range of conversation for sure. I did read a article a great while back where they were "wet flow" porting cylinder heads so that when moist air was flowed through heads, the condensate track On the combustion chamber trailed towards the spark plug for a more complete burn when ignited. The "soft head" concept seems very sound generating some pretty astonishing results. Quite an improvement over the traditional "squish and quench". Definitely worth a good read...
Comment by R. Randall Halton on November 17, 2014 at 9:44pm

photo courtesy of the Clover Club, NY NY and

Comment by R. Randall Halton on November 17, 2014 at 9:28pm

Wow, sounds like we all should be camping and cruising together. My comment didn't even get posted in Jeff's column. I don't think its internet jargon. I been with people, same interests who were talking the same thing, and no one understood what the other was saying. Time for another drink, maybe a "Blue Blazer".  Pres. Grant like them. Blue Blazer is a Flaming Whiskey. Might be where the term, "Lets fire one up" came from. Grant used to ignite his drinks with a cigar. Generational lingo. Here's a sight David you and your Wife might enjoy.

Comment by david craft on November 17, 2014 at 7:41pm

Flame:  To insult someone electronically.  there are links to the internet jargon which is pretty much endless and some would argue mindless.  I will try to make my humor more apparent in the future...personally not really liking the dry stuff

Comment by Rich Thomas on November 17, 2014 at 6:20pm

Ooooh! sorry I'm new to the forum thing, usually just lurk but I've found something here that has pulled me in and I like it. Maybe some of you long Timers can put together a terms and acronyms list/guide for us newbies.



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