Need Advice

[levisjohnson]

I have an 88 Crew Cab with the 6.2 Diesel in it.  I want to keep the diesel I think.  It has 115k miles and runs really well.  I plan on converting to a SWB bed and convert to 4 wheel drive.  I have a Turbo 400 trans.  I plan on driving this on the highway a lot (so I would like overdrive) and pull the occasional goose neck (will be used for light farm use).  I want to put 33-35 inch tires with 18-20 inch rims.  Questions are:

-What gear ratio for the front and rear end?
-Keep the 400 or get a 700r4 or something different?
-keep the diesel or convert to gas?
-Any other advice you may have?

Thank you in advance for your advice.

Levis

[BlueCollarRon]

It sounds like you got to do a lot of converting in my opinion.  That is a nice truck as it is, I would just find a 4wd swb with a 700r (if you want the overdrive).  My truck is like what you are looking for except I have the 350 turbo.  The 350 and 400 turbo are both very strong trannys whereas the 700r is expensive to rebuild and doesnt like abuse.

Nice truck though.

[Captkaos]

1)Gear ratio for axles and 33 or 35's: 3.73 or 4.10
2)700R4
3)it sounds like you want to keep the diesel
4)converting one to 4x4 will require a donor and it would need to be an equivalent donor (1T 4x4)

[levisjohnson]

Thanks guys, but I forgot to ask about the T case.  Which one should I get.

Could I just get a 3/4 ton donor, my truck is 3/4, not a 1 T.  I have a late 83-87 burb frame that I am getting parts from.  I have built a 72 and put a 54 GMC on a 79 frame from the ground up so the complexity is not the issue.  I am just not sure what combination of components I need for the drive train.

[hilton850]

For what it's worth, my dad bought an '85 chevy 1/2 ton 4x4 with the 6.2 diesel and the 700R4 and had really bad luck with both.  The diesel didn't make any power and liked to munch the 700R4 transmissions.  after the third transmission in 2 years the shop would only warranty their labor and dad had to start paying for parts.  after the 7th transmission in 4 years he traded it in.  He didn't even do that much towing with it, mostly used it to get back and forth to work.  He also had to put more than one set of head gaskets on the engine.  Only good thing about the truck was it got about 20 mpg.

If you really want to keep the engine I'd stick with the TH400.  I know those came in at least some 3/4 ton trucks (not sure if it was in all the 3/4 ton autos or not) and in the 1 ton trucks.  Front axle out of any 3/4 ton or 1 ton 4x4 with the same body style should work.

If it were mine, I would find a 350 "M" code gas engine (from a heavy 3/4 ton or 1 ton) because it would be a good comprimise between power and economy and be much more reliable (in my experience) and does pretty good towing.  Personally I would just use the th400 tranny and some 3.73 or 4.10 gears (depending on how much towing you plan on doing...4.10 is good for towing) and let the thing rev a little on the highway.  My brother had this setup in a reg cab long bed truck he had except 4.10 gears and that thing towed like a champ.  He had stock tires on it so it revved a little extra on the highway but still got around 12 mpg.  I suppose you could also build a 700R4 that would work pretty good but I've had bad expereinces with those.  You can find either transmission with a NP208 transfer case, which should work just fine for what you want to do with it.  Sorry for the long post...just my $.02

[VileZambonie]

Sounds like your dad needed a different mechanic.

700R4, 3.73:1, and a 208 will work just fine and will be readily available from a donor. You can keep the diesel but when it blows up go gas.

[levisjohnson]

Thanks everyone for your input.  Vile, you and Chris are always right on.  I agree with a lot you two say but I keep quiet.  Hilton, I had a friend of mine rebuild a 700r4 for me and when I picked it up it weight about twice as much as the stock core I took him.  It has been in 4 different trucks and I think its still kicking in the old 54 deluxe body on the 79 frame.