Mothership transmission advise wanted - 1985 GM based motorhome

G

Greg Miller

Well-known member
Lucky for me it made it home and didn't brake down far away but all is not right with the torque converter on the mothership / car hauler. It seems to be locked in no slip mode. There is over 100K on the rig and it currently has the THM400 3 speed.
Will a 4L80 bolt in - giving me overdrive? I assume that is what they put in the later model 454 GM based motorhomes.
I also assume I want the 4L80 not the 4L80e so it doesn't require a special computer.
Where is a good source for used heavy duty truck trannies?
Any other advice?
I gotta keep the cost down so I have money to race - and the ol' motorhome ain't worth much anyhow.
Thanks,
 
Thanks Mike. I knew I could cure it with mega bucks.
Remember me, member #2 in Dirt Cheap Racing? Sage was #1, with a 1985 Ford pick up, tow dolly and an E30 318. He ran NCW for 2 years after upgrading to Area so he could get more race time in.
In his footsteps are Eric Blois and Tucker Sheppy who drive their cars to the track, race em and drive home.
 
Thanks for the feedback Bill and Dave. I have a possible lead on a used TH400 from a '99 motorhome with low miles. That would be a drop in for sure.
If the old mothership didn't have other issues the 4L80E with a shift kit sounds like a way to go.
I would need to relocate the tranny mount and get the drive shaft shortened from what I can glean from the web.
A local tranny shop suggested I check the governor, but it looks good. So much for a quick fix.
I'll let everyone know what happens so others might learn from my mistakes or successes.
 
Ken Killam said:
I think it needs a new logo.

A four letter word starting with 'F'. ;-)
Click to expand...
You sure it is not 6 letters - putting it in the proper tense? _ _ _ _ ed
Tranny shop now says it may be a torque converter only. With me doing all the labor around $300 with a fluid and filter change.
 
A better idea
fordlogo2003.jpg​
 
Greg,
Check out Walt and Verns in Buckley off of hwy410. My father put a 4l80 in his dually. Converted from 3spd manual. Yes on the non electronic, they will know what you need.
 
Greg,
Two tow vehicles ago, I had a mid-80s chevy van with a 305 and a TH400. Had the TH400 rebuilt after about 100,000 miles of work related abuse at the hands of young drivers. The rebuily unit had an aftermarket shift kit in it, and came with a supposedly stronger torque converter. That tranny took the van to it's grave (actually it was sold and killed shortly thereafter by the new owner) at over 300,000 miles (just shy of 500,000km). It won't help your gas mileage, but in my experience a TH400 is a pretty robust piece of work. If you skip the torque converter and shift kit, a rebuilt that you install yourself is less than a set of (new) tires.

Martin

Greg Miller said:
Lucky for me it made it home and didn't brake down far away but all is not right with the torque converter on the mothership / car hauler. It seems to be locked in no slip mode. There is over 100K on the rig and it currently has the THM400 3 speed.
Will a 4L80 bolt in - giving me overdrive? I assume that is what they put in the later model 454 GM based motorhomes.
I also assume I want the 4L80 not the 4L80e so it doesn't require a special computer.
Where is a good source for used heavy duty truck trannies?
Any other advice?
I gotta keep the cost down so I have money to race - and the ol' motorhome ain't worth much anyhow.
Thanks,
Click to expand...
 
I got the tranny out - no small feat - but with a tranny jack, a come along, lots of card board, and the removal of the front passenger tire, the tranny made it to Kirkland Transmission. It is now up to them to clean it up and make it work again with a new torque converter. The oil in the pan looked like a rich gold strike. A bit from the one way Formsprag clutch was in the pan.
But everything says the TH400 tranny can take a lickin and keep on ticking. It DID get me and the race car with spares ~22K lbs home.
I'm glad I didn't opt to get a used tranny from a lower mileage motorhome that was being parted in a farmer's field. I wouldn't have had all the necessary equipment (including a short saw horse) with me.
We will see how much it hurt$ next week.
The Mothership will live to see another race.
 
Update:
Kirkland Transmission went through the trans and discovered a really thin second gear clutch in addition to the bad Tq Conv. They rebuilt the tranny, and installed a new OEM Tq Converter with new improved shift kit, and included an inline filter for the return line to catch anything I couldn't clean from the cooler loop. Total damage $1400 plus 4 gallons Dextron III. It of course works like a champ now. If I was planning on keeping the motorhome another 8 years I would have opted for the Allison torque converter (+$150 or so).
So I'm good for another 100K or 30 race seasons ;)
Thanks for your suggestions all.
 
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