Opinions on the 4L80E Transmission vs TH400

Gjac wrote:
What are you getting now with your 3 speed, and how much does your MH weight? I have a 1996 GBM on a 95 chassis with the 4L80E and I have averaged 8.6 mpg over 85k miles. It is 33 ft and weights about 15,500 lbs and seldom comes out of OD since I installed headers. It will stay in 4th gear if I am above 45 mpg on a flat road. I have 107k miles on it and have changed fluid and filters 3 times. I think it is a good transmission.

Hmmm. Sounds like it.

7 MPG... if I keep it to 60 MPH. Worse when pulling the boat.

I think her GVW is around 12. Only a 23 foot Class A.

I just got off the phone with my transmission guy. He said I could figure double the cost to rebuild. But he likes the transmission. Says the 400 is always slipping by one to two hundred RPM where the 4L80E has a lock-up converter. This keeps the heat down along with the mileage benefit.

BUT... he reminded me of the MEXICOWANDERER factor. My turf IS hilly. Most of our camping is done within 3 hours of home and most of it is hilly. Only on longer runs would I get some decent straightaway time.

BUT... with 8.6 MPG, I might be less inclined to enforce that 3 hour radius restriction and allow us to venture further more often.

I think it's fair to say that the difference is relatively negligible. If I find an '89 that I love at a great price... then... great!

If find a '92 that tickles my fancy... well then that's great too. And if it has low miles by chance... then I might be selling it well before a rebuild is due anyway.

Thanks!

Gears are nice, if the transmission is sturdy. Quicksilver is 22,700 lbs empty as she sits. Was close to 25K with the generator*. With the Fuller 13-speed, I get 16.4 mpg on the flat. With the toad 14.1 Worse case is 11.3 towing to Patzcuaro, a steep climb to 7,000 ft. 8th and 9th all the way. The trans is a 10/5/13

(10) 11:00 X 22.5" tires

Unless you do a LOT of flatland driving, I wonder if OD is worth jumping through hoops for...

What are you getting now with your 3 speed, and how much does your MH weight? I have a 1996 GBM on a 95 chassis with the 4L80E and I have averaged 8.6 mpg over 85k miles. It is 33 ft and weights about 15,500 lbs and seldom comes out of OD since I installed headers. It will stay in 4th gear if I am above 45 mpg on a flat road. I have 107k miles on it and have changed fluid and filters 3 times. I think it is a good transmission.

If your turf is hilly overdrive is sort of silly...I didn't say it, a rebuilder did.

New is one thing
20-some-odd-years old quite another. Save fifty bucks on gas and spend $300 on sensors and diagnostics is questionable. I might add had you owned the rig since new that would tint the situation even more. Call a rebuild ship and ask them the out-the-door quote for both units. That answer alone carries some weight. Looking and weighing always pays dividends.

The 4L80E in my rig has been flawless with 75,500 miles.

The TH400 and 4L80 are among the most reliable Chevy trans ever made and probably have equal durability all else being equal. Of course the TH400 is simpler which is cheaper to rebuild and doesn't require computers. The 4L80 has OD and is slightly more efficient even in direct, but requires computer control and has more expensive parts. Of the two, the 4L80 has more possible failure points. Either trans should serve very well if in an OEM situation (good engine and final gearing match.)

If you have two RV's you are comparing, one with the 4L80 and one with the TH400, and both are stock, I would find something else to base the decision on.

You are looking at late 80's early 90's rigs, they probably aren't really going to have the HP to be in OD too much anyway - especially at 60 MPH. MPG difference at 60 MPH will probably be very small if any. Any savings would be lost at trans rebuild time. If it were my RV I would lean TH400 based on that - all else being equal. If it were my DD pickup, I would go 4L80 all the way. Just my opinion.

KendallP wrote:
Good afternoon,

I was considering a late '80s MH when it occurred to me that I could get an OD if I opted for an early '90s unit on a P30. The searching of done so far indicates that the gradually improved on the 4L80E since it's intro in '91. Some opinions on this would be appreciated.

And how about durability vs the ol' Turbo 400?

Also... what kind of average mileage improvement can one expect between a P30 MH with a 3 speed and a P30 with the OD tranny doing, say 60 MPH?

Although this is a tech-ish issue, you might get more responses by having a mod move it to tow vehicles. The first question I can't comment on but you should see a couple mpg increase with an overdrive.