Recommended 4L80E HD/Towing Mods?

Hello All,

I've got a '91 R2500 Suburban (fleet model, ex NYC fire truck) with an NA J motor and a first year 4L80E (no tow/haul mode, and just a regular 'P R D 2 1' shift indicator), and a 3.73 rear end. Roughly 126K on the clock.

If you believe the factory VIN decoder, this truck is rated for #9000, which says to me about #6300 max towing, realistically.

I've just picked up a #6000 boat which I'll be towing this summer. So aside from the obvious engine mod questions (I've already posted in the 6.2 forum, http://www.thedieselpageforums.com/t...d.php?t=26481), I've got some questions about my 4L80E, and what I need to do to prep it for hauling #6000 on a regular basis.

1) Do I need a shift kit? If so, whose? Transgo? B & M? And which kit (if they offer more than one)?

2) Should I replace the factory trans cooler with a larger model and a dedicated fan?

3) Do I need to get a higher capacity, finned oil pan?

4) Should I pick up an electronic shift controller to add a tow/haul mode to this trans? If so, whose?

5) I'm thinking a trans oil temp gauge is a must here, so I don't fry this thing, right? If so any recommendations?

What else might I be missing here?

TIA for all replies,

--Duncan

I have an HD (rebuild) 4L80E in my motorhome. I did replace the pan with one from Mag HyTech http://www.mag-hytec.com/Transmission_pans.htm

and it helped with cooling - partly because it increased the capacity. My motorhome generally runs at 16 K lbs.

A transmission temp gage is worthwhile, IMO.

There are problem areas in the older 4L80e's which can be identified through folowing site; http://www.transhardparts.com/

Sonnex is the #1 upgrade for all transmissions w/issues from factory.

A quality bullet proof HD off road 4L80e can get costly quick, if truck is keeper then the $$$$ is worth it.

If you need a good replacement @ a good price check Jasper. We have very few warranty problems. For a very good production transmission with an excellent warranty find Jasper Engines and Transmissions on the web. Trans warranty is 3 yeras 75000 miles most applications. Jasper updates to all the latest factory specs and also works with several OEM's to improve life of their products.

My 95 Suburban came with the large factory cooler. I put on a deep finned pan, but I never thought that I needed it. I did put 3 gages in a pillar pod. A good idea, having a transmission temp gage.
I towed around 6000 lbs for maybe 60 K, before I extended the tongue on my trailer and added about 1200 lbs to it, in the process. I put on another 40 K after that and never saw more than 230 deg temp. Usually saw less than 180. But, I did have that big cooler up front, so I don't know what to say about your rig, except to put a big cooler up there and a gage in the dash. Pretty good idea to change and flush the fluid. With these few things, I bet you would be good to go.
DW:)

Next tranny fluid change - put in synthetic too. It'll give you another 40 so degrees of heat tolerance to the fluid if you heat it up.

I think the Synthetic ATF will be one of the best things you can do. Mobil 1 or Amsoil come to one mind. $120 of Mobil 1 will go a long way to helping your transmission. Increased capacity of the ATF cannot hurt. The 4 quart pans add about 25% more volume to the system. Have yet to see any real data on aluminum pans vs steel pans in relation to ATF temperatures.