A Tale of Two Transmissions?

[Carl Bice]

Ok I searched for this answer, and if I missed it I do apologize.
But , I currently own a 1973 Sportscoach, and although I would love a newer unit, this is what I have to work with, And we are really having a ball, making this thing fit us.
But Our problem currently, is one I am not really familiar with. We have a 454, mated to a turbo 400 tranny, and I lost reverse in it, now, I have found a guy that can rebuild it for a good price, which would be fine, except for what happened today.... I stopped at another local shop today, and we got to talking about the tranny issue, and this new guy, mentioned changing my tranny to a 700R? all I know is that instead of a 3speed, the 700R is a four speed. now My question is, if I can find a 700r to match up to my motor and driveline, and had it rebuilt to heavy duty specs, just like the 400, would it be worth it? This new guys swears by it, saying I would gain another gear, and better reliability, and added MPG.(minimal I'm sure) but I do know the 400 is a pretty solid unit in itself?
I am Hoping some one here can help me decide between the two... Or Should I just leave well enough alone?

[tncruiser]

your 400 xmission sounds like it held up for forty years .that will make your rig 80 yo at next replacement ,that means it will be a problem for you great grand kids
brianj

[Burban]

The 700r4 are good but they might not last with the 454 and weight of the mh, the one that you what if you are going to up grade to is the 4L80e transmission, the make a stand alone controller for the tran and wire harness that you can buy.

[GOLDWINGER2]

Repair the 400 and enjoy the MH.

[Nick-B]

Burban has it right on. The 700R4 is too weak. Another option is to stick with the 400 and an add-on overdrive unit.
Best of luck!

[Carl Bice]

Originally Posted by tncruiser

your 400 xmission sounds like it held up for forty years .that will make your rig 80 yo at next replacement ,that means it will be a problem for you great grand kids
brianj

Heck both my boys are already arguing over which one get's it... when we get a newer one, they are loving the rebuild..We have a 28 and a17 yr old, they are a great help.

Oh , please do me a favor, and Drive down close to Chattanooga, and tell my hometown, I'll be back that way soon, lol, we really miss that part of the country..

[Carl Bice]

Originally Posted by Burban

The 700r4 are good but they might not last with the 454 and weight of the mh, the one that you what if you are going to up grade to is the 4L80e transmission, the make a stand alone controller for the tran and wire harness that you can buy.

Looking into this, but still concerned if the possible advantages will ofset the cost of the upgrade? it is after all a 40 year old rig.. And the more I research the old 400, I am finding it to be a really stout tranny? But as always I am looking for any improvement on my mpg.. I already have my electronic ignition lined out to do. and researching on possible intake and carb changes... Anymore advice? Planning on exhaust upgrades, and improved cold air intake already.trying to make this turnip bleed aint easy..

[Carl Bice]

Originally Posted by GOLDWINGER2

Repair the 400 and enjoy the MH.

I am beginning to agree, it sounds like the best possible solution thus far..And we really want to get this thing moving..AS DW says we are getting itchy.... ready to roll.

[Carl Bice]

Originally Posted by Nick-B

Burban has it right on. The 700R4 is too weak. Another option is to stick with the 400 and an add-on overdrive unit.
Best of luck!

Do you know where or who to check with on an overdrive unit? being an ex semi driver, I keep thinking about a splitter on the rear axle? but not sure if that is even possible on a motorhome? Or Feesible.... Just a thought?

[Carl Bice]

Fleemarketer posted this on the 700r4,http://www.irv2.com/forums/f65/a-goo...ml#post1232835 It is a very good read..

[lonestarace]

Originally Posted by Carl Bice

Do you know where or who to check with on an overdrive unit?

Replaces the tailshaft housing.
Gear Vendors under/overdrive transmissions the most awarded auxiliary transmissions.

[cook elandan]

Everybody has their opinion..I am going to replace my transmission with the 4l80e, it is an upgrade from the 400..it is built with many parts from the 400 and can be built to handle just about anything..Yes you do need to find or buy the controller for it, but money and time are always issues..Go ahead and rebuild the 400 and then get you a 4l80e and start getting it ready for a swap...you will need to change mounting spots for crossmember and parking brake if attached to tailshaft..drive shaft will have to be resized also...get est. to see if the cost and ben. is worth it..for me the lower RPMs and fuel savings is what I am looking for, besides running down the highway with the tach screaming at 3grand putting strain on engine and the heat..the overdrive will help..you can go gearvendor but too much for my costs..
I am same as you and always looking for up grades...looking to install either a TBI unit or Vortec FI system instead of q-jet. I am leaning more with Vortec because if I get the right one the computer will run the 4l80e with reprograming the chip.

[Burban]

Cook, if you are going to do that swap, look for a one ton van/pickup or 3/4 ton sub about 87-92.You didn't say what year or motor you have, the intakes bolt angel is differently for TBI motors also if you find above with 350 the TBI has a different cfm which would In turn result in bad mpg as well , I have a van and sub both have 4l80e's but one has 350 the other has 454. The computers and wire harness are the same the chips are all that is different, if you buy a hole truck that would be cheaper in the long run and you would not have to hunt down parts. I'm thinking about putting the 350 in my sub and the 454 and 4l80e from the van in my mh.

[cook elandan]

Sorry, have a 454 in MH.