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Old 09-08-2010, 10:40 PM   #1
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1981 28' Airstream 280
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Allison questions / how many cans of worms can a 28' motorhome hold

After a year spent reviving Dads 81 28' turbo diesel 10 days before maiden voyage , the allison loses reverse, inspection showed rust on internals from sitting , Dean pulls tranny and rebuilds ( very simple trans actually ) as luck goes with this project , the third time trans was installed it works, made the maiden voyage. Having never driven this yacht before or really looked at the mechanics and the pathetic lack of information available can anyone tell me , were the diesel units factory built or converted , as mine appears an cobbled up afterthought, Trans is a AT545 4spd, no park model , I suspect it is wrong appliaction , 1st 2 shifts ok, last 2 have to run the engine up against the governor then lift to get it to shift, this after canning the vacuum modulator and installing mechanical modulator a turbo diesel would demand , valve body needs reworked, Once we get the trans issues worked out, and can locate a speedometer gear for said trans and get speedometer to work ( which has been total exasperation , Airstream/ Allison / GM absolutely no help ) we ask the question are these Isuzu turbo diesels really the dogs they appear at first and should I just buy a rolled Dodge and put a real diesel in it , or add a hitch and make a trailer out of the thing
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Old 09-10-2010, 09:14 AM   #2
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I can confirm that a 28' can hold less cans of worms than a 34'...
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Old 09-10-2010, 10:02 AM   #3
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That's odd, I did not know AS installed Allisons in the early mo/hos. Ours is a GM turbo that a guy in Idaho hot-rodded for us with some Allison parts, works perfect. Without a overdrive, the Isuzu engine is indeed a slug, but remember what the speed limit was back then.With a o.d., we can do 65mph @ 3200 rpm. Fuel mileage is a steady 15mpg. Those engines are tanks, ours burns no oil.
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Old 09-15-2010, 12:49 AM   #4
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I'm with Mike, I thought they only used the Chev TH400. It appears Airstream did the conversions in house. I talked to a guy who said he talked to the mechanic at Airstream who actually did the conversions.

Diesels can drive gasoline designed transmissions but they have to be set up properly. Allisons have to have the proper torque converter set up for engine rpm and torque. The TH400 had some clutch and valve body mods from Airstream. When a diesel fires the pulse and vibration is different than that of a gasoline engine. This also can create problems for a trans designed for a gas engine.

Allison should be able to set you up with a speedometer drive. You may have to buy a ratio change gear-box to get the proper ratio for your dash meter. Any good speedometer shop should have what you need. These are simple mechanical speedometers.

Keep in mind that this is a 30 year old coach built on a truck chassis. The Isuzu is not a modern ball of fire but it will do a fine job of propelling your coach down the highway for many, many miles. Mileage in the 14 - 15 mpg range beats just about any similar sized coach on the road today.

I have a '92 Dodge Cummins and with a trailer with gross weight similar to the Airstream not much difference in power and worse mpg. The newer computer engines do better but for a 30 year old mechanical diesel the Isuzu does just fine.

Good luck, Dan
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Old 09-15-2010, 11:54 PM   #5
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Reasons not to install an Allison AT545 in your motorhome

Turbo 400's work
you can't trip over a column shifter
allison holds 5+ gallons of atf
allison has no (park) feature
allison offers NO speedo gear
Allison want's 400.00 for a new governor and can't tell me which part # my governor is by the printed code they put on them identifing specs
speedo gears removed from 2 core transmissions bearing same model number as your transmission won't work in your transmission
There are better things to beat your head against
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Old 09-16-2010, 01:20 AM   #6
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Originally Posted by Dean Rawson View Post
Turbo 400's work
you can't trip over a column shifter
allison holds 5+ gallons of atf
allison has no (park) feature
allison offers NO speedo gear
Allison want's 400.00 for a new governor and can't tell me which part # my governor is by the printed code they put on them identifing specs
speedo gears removed from 2 core transmissions bearing same model number as your transmission won't work in your transmission
There are better things to beat your head against
Wow, I can tell you've had a fun day. Do you know the origin of the Allison installed in your Moho? Was it done at Airstream or elsewhere? I assume from your post that you have been talking to an Allison help line or tech center. It doesn't surprise me that aren't much help on a one of a kind install in a 30 year old vehicle. I suggest you look for a vendor that does Allison rebuilds locally. You will have better luck finding somebody familiar with the older units. There are a bunch of Allisons on the road in older trucks and buses and many shops to service them while the manufacturer is more interested in selling and dealing with new units.

If you have any problem finding a shop send me a PM. Several years ago I used to deal with a couple of shops in Seattle that were very knowledgeable and helpful.

Good luck, Dan
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Old 09-16-2010, 08:37 AM   #7
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Closer to you would be the shop that hot-rodded my Turbo trans. Great guy, lots of parts lying around. Wayne's Transmission, 4873 Valenty, Chubbuck, ID. # 208.237.1833. Chubbuck is just north of Pocatello. Say hello for me, he let us stay there while he re-built the trans.
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Old 09-17-2010, 12:51 AM   #8
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Thank's for the moral support Dan & Mike , im sure my Dad had this allison installed by a shop too close to the border when he lived in LA and its never been right . Old boy from a wrecking yard in eastern Idaho sent me a governor and speedo gear for $50.00 and told me alot about allisons , gave me some direction .
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Old 09-17-2010, 01:45 AM   #9
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Keep at it Dean, once you get all the bugs worked out you should have a bullet proof set up. Unfortunately you have a one of a kind install so it's difficult finding help. You just have to be creative.

I have been fighting a vibration problem on my Moho and have been trying everything. I finally installed two trans mounts back to back and I think I solved the problem. It has been a two year battle involving visits to several very helpful shops. The bottom line is the coach is finally driving the way I think it should and the effort was well worth it. If nothing else I've learned an awful lot about the drive line an suspension on these Mohos.

Good luck, Dan
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Old 09-18-2010, 05:24 PM   #10
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Quote:
Originally Posted by Dean Rawson View Post
Turbo 400's work
you can't trip over a column shifter
allison holds 5+ gallons of atf
allison has no (park) feature
allison offers NO speedo gear
Allison want's 400.00 for a new governor and can't tell me which part # my governor is by the printed code they put on them identifing specs
speedo gears removed from 2 core transmissions bearing same model number as your transmission won't work in your transmission
There are better things to beat your head against
My 'Silver Bullet' has an Allison 545. The OP had it installed. The trany was build by a 3rd party and the number mean nothing to Allison. Mine is in need of an over haul and I found the paperwork and called the shop that built it. You can not deal with the Allison people at all. Find a truck trany shop. I found one in Texas I'm going to take mine to when I get back home from this bicycle ride I'm doing on the west coast.
mel in Santa Monice living in a hostel tonight.
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Old 09-24-2010, 06:51 PM   #11
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Well I'm home. Tried to find a Isuzu diesel to just do a transplant. Can find none! Seems the Mexico's (don't know which ones) are buying all they can find. I saw a lot of them (running) in California, but none in junk yards. What's the deal? Guess I'll pull my trany and get it rebuilt. May be it's time to do that engine overhaul and turn it into a 496 while the trany is out.
mel
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Old 09-25-2010, 09:29 AM   #12
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Mel, pick up a rolled dodge and go with the cummins , have some real torque , bring that tranny by and I'll rebuild it for the price of a kit ( 350.00 ) and and a 12 pack.
Dean
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Old 09-26-2010, 06:52 PM   #13
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Mel, pick up a rolled dodge and go with the cummins , have some real torque , bring that tranny by and I'll rebuild it for the price of a kit ( 350.00 ) and and a 12 pack.
Dean
Thanks for the offer Long way from here to there. Been checking around and seems like any and all Isuzu's end up going to Mexico before they stop rolling. But then, how may 6-packs is if from here to there.
Got to do some more checking. Going with a Cummins, I'd look for an 01-02 I think. Got to get my back working on first.
mel
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Old 09-26-2010, 08:54 PM   #14
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Thanks for the offer Long way from here to there. Been checking around and seems like any and all Isuzu's end up going to Mexico before they stop rolling. But then, how may 6-packs is if from here to there.
Got to do some more checking. Going with a Cummins, I'd look for an 01-02 I think. Got to get my back working on first.
mel
Mel, I didn't catch do you have an Isuzu in your coach now? If so is it hurt or are you planing for the future?

The Isuzu is a pretty tough engine and does reasonably well in the AS. The Cummins is a great engine but the changeover can get to be costly. If you stay with the Allison you might consider an early mechanical Cummins. The newer electronic engines want to talk to the trans and electronically connecting your trans to the Cummins computer can be a challenge. A transplant engine/trans package may be a better solution.

On the other hand doing an in-frame overhaul on your Isuzu will probably enable it to live longer than your coach and save you lots of bucks.

Just a few things to think about, Dan
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Old 09-27-2010, 03:48 PM   #15
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Mel, I didn't catch do you have an Isuzu in your coach now? If so is it hurt or are you planing for the future?

The Isuzu is a pretty tough engine and does reasonably well in the AS. The Cummins is a great engine but the changeover can get to be costly. If you stay with the Allison you might consider an early mechanical Cummins. The newer electronic engines want to talk to the trans and electronically connecting your trans to the Cummins computer can be a challenge. A transplant engine/trans package may be a better solution.

On the other hand doing an in-frame overhaul on your Isuzu will probably enable it to live longer than your coach and save you lots of bucks.

Just a few things to think about, Dan
Oh! sorry! No I have a gas 454. My dream was to find a '05 or younger N-series Isuzu wreck and replace the Gas with Diesel, but it ain't gone-a happen.
Did some checking again today. Found a good shop who will build a 6L80e. The headache is, I need a wiring harness to go with my '90 (added on) GM EFI, cross member, change the drive shaft, york, a shifter. Have heard of places that can remap the computer to work, will see.
Wish my '01 Dodge Diesel was automatic. The truck would be scrap metal by now. That baby will haul butt!
I got some calls and emails in to some people.
mel
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Old 09-28-2010, 01:32 AM   #16
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Oh! sorry! No I have a gas 454. My dream was to find a '05 or younger N-series Isuzu wreck and replace the Gas with Diesel, but it ain't gone-a happen.
Did some checking again today. Found a good shop who will build a 6L80e. The headache is, I need a wiring harness to go with my '90 (added on) GM EFI, cross member, change the drive shaft, york, a shifter. Have heard of places that can remap the computer to work, will see.
Wish my '01 Dodge Diesel was automatic. The truck would be scrap metal by now. That baby will haul butt!
I got some calls and emails in to some people.
mel
Why don't you forget the 6L80e and just find a Dodge automatic for your '01 and stuff the package in your moho? You are going through most of the hard stuff to add the 6L80e, just do the same effort and add the Cummins in front. Fabricate front motor mounts and you are there.

Go for it, Dan
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Old 09-29-2010, 01:34 PM   #17
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Why don't you forget the 6L80e and just find a Dodge automatic for your '01 and stuff the package in your moho? You are going through most of the hard stuff to add the 6L80e, just do the same effort and add the Cummins in front. Fabricate front motor mounts and you are there.

Go for it, Dan
Need a 6L that's rebuildable The one's I've found are built and cost around $4000 and then the harness/control system is another $1300.
Keeping an eye on craigslist.
Keeping an open (or is that absent) mind.
Been looking for a Dodge wreck with a cummins/auto for a while. The few I've come across were either manuals, or crushed too bad.
I'm on drugs right now, so, I'm not going to start it yet.
mel
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Old 10-04-2010, 04:09 PM   #18
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[IMG]file:///C:/Users/Mel/AppData/Local/Temp/moz-screenshot.jpg[/IMG]
I have started building some ramps. I still haven't decides which way to go, rebuild the Allison 454 ($1650) and still get 6mpg. Or go to a 4L80e (no controller available for a 6L). I can get the transmission ($2200); controller ($1300); driveline reworked ($150); build or find a cross member ($???); get the park brake to work ($???); Unknown other ($???). I'd get a mile or 2 more per gallon, the road RPM would be lowered, and I can build more power into the motor later.
Maybe I need to drink some more beer the think about this.
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Old 10-04-2010, 04:20 PM   #19
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After spending a ton of cash and getting not too improved mileage, I'd keep the 454. The heat was the big problem with those engines, but for a fraction of the cost of what you're considering, that can be taken care of. Have another beer; it's not worth it.
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Old 10-04-2010, 06:49 PM   #20
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[IMG]file:///C:/Users/Mel/AppData/Local/Temp/moz-screenshot.jpg[/IMG]
I have started building some ramps. I still haven't decides which way to go, rebuild the Allison 454 ($1650) and still get 6mpg. Or go to a 4L80e (no controller available for a 6L). I can get the transmission ($2200); controller ($1300); driveline reworked ($150); build or find a cross member ($???); get the park brake to work ($???); Unknown other ($???). I'd get a mile or 2 more per gallon, the road RPM would be lowered, and I can build more power into the motor later.
Maybe I need to drink some more beer the think about this.
I would be very wary of using your ramp. There is nothing to keep the whole set-up from going forward or backward and the whole thing collapsing flat on the ground. Also the top plank wants to be doubled and probably twice as many vertical supports. If you really want to use wood solid is best. Buy several boards and stack them flat on top of each other to reach the height you want.

I would also hesitate a trans change. You are looking at $4000 and at a 10% gain in mpg you need to spend $40000 on fuel to break even. Fix the Allison if it needs it and enjoy your coach. If you want to drop the rpm some change the gear ratio in the differential. It can probably use some fresh bearings and while you have it apart a new ring and pinion is only a few bucks more and now you only need to worry about the engine drive-train wise.

Good luck, Dan
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