6.2 Running RPM's

[70chevelle]

I just bought a '84 motorhome with the 6.2. It has a Banks Turbo added to it and 4.11 rear gears. The thing turns 3200 RPM at 60 and has 80,000 miles on it. The tranny is a TH400.

My question is on the a gear change. I am contemplating going to a 3.73 or 3.42 ring and pinion to ease the stresses at cruising speeds. The guy I bought it from pulled a horse trailer with it all over and never had any problems; however, I am not pulling that much and would like to be able to cruise at 65 without thinking its going to blow.

What do you experts think????

This is my first diesel.:D

[DmaxMaverick]

Welcome to the Forums!

I suggest keeping your gears. You will very likely get into a situation where you will need them, especially with a M/H. The best thing you could do with what you have is replace the TH400 with an OD tranny. A 4L80E with a stand-alone controller would give you the best of both worlds, and run cooler at the same time.

[john8662]

Identify which gear ratio you have, then go from there.

If you have 4.10 gears, then leave it alone, but if you have 4.56 then consider a swap, otherwise, the OD tranny is the answer.

J

[Craig M]

If you have an 84 motorhome then a 700R4 transmission might be better to install than a 4L80E. The 4L80E will need an electronic adaptor to work with your non electronic vehicle (around $1000). Another option, that a number of folks have done is to add the Gear Vendors auxillary transmission. It gives you the overdrive in 3rd gear for your TH400, and the OD is also available for 1st and 2nd gears also. Used Gear Vendors can be had for $1000 to $1500. New ones are around $2500 or so. Used/rebuilt 4L80E's are not cheap. A built up 700R4 can be around $2000 or so. Depending upon what you have access to can efffect final pricing. All three options will give you lower rpm's on the freeway. Gear Vendors adds additional gears of hill climbing.

[Mr. Bone]

this thread caught my curiosity because i have a 3spd auto tranny w/4:10 ratio. . .BTW i have no idea what 4:10 ratio means. Even though i have not installed a tach i can tell by the engine sound @60mph I'm nearing my limit. Wondering what my options are for the van to feel comfortable at 70mph. The "gear vendor" seems like a option or not? thanks.

[west85]

I swapped in a 700r-4 into my truck originally equipped with a th-400. Got it from a junked suburban and rebuilt it, if your looking for cheap. If you do want to go that route make sure you get a diesel 700-r4. You would have to get a 27 spline yoke, shorten the driveshaft, with common 700r-4 tailstock, move the crossmember ahead, or modify the tranny mount, and you would need to get the tv cable backet and set up off of the doner truck. A brake switch and trottle positioning switch will also be required for the lock up converter to work correctly. It's a job, but I thought it was well worth it.

[Robyn]

A 700 is not a bad tranny "IF" its built right. The factory ones were never meant to handle a MH Drop a gear vendors OD unit up behind the 400 and you'll be set. Just mount the unit shorten the drive shaft and poof, best of both worlds.
The 400 is tough as nails and will hold the 6.2 all day long. To build a 700 is costly. It can be done and would work fine BUT be prepared to drop $2000 in a K case 700 to get the reliability.
For severe duty on a 700 you would also need to install a HD NON lockup converter too. The 700 converter clutches and other innards of the converter are not stout enough.
Most good tranny houses can set you up with a non lockup unit at a right price. Also it requires some internal mods when the tranny is being built so you can use a NON lockup.
I have built a couple this way and they work great. You have a deep low gear (slightly better than 3:1 and an overdrive).
The non lockup converters are larger in that without the clutch unit they have larger internals and generate less heat and are more efficient. The small loss you have by losing the lockup is far outweighed by the added reliability.

Good luck and keep us posted

Robyn