78 GMC Pathfinder 4x4 build

[barefoot boy]

Clay, it is generally acknowledged that the later the year of the 700R4, the more fixes GM made to the problems. Specifically, late 1987 and later years have the auxiliary valve body and are the best according to most sources. As far as bolting a 700R4 into your van, all years of the 700r4 will be the same. The only computer controlled function of the 700R4 is the torque converter lockup. There are a number of ways to control the lockup converter without a computer; I used the TCI lockup kit that uses a vacuum switch to lock up the converter only in 4th gear. It works OK, but an internet search will give lots of opinions on the "best" way. Are you sure your van has a Turbo 350? If it is a G30 or G35 it most likely has a Turbo 400 and the swap becomes more complicated and expensive as the Pathfinder spud shaft is no longer usable. Do you know your gear ratio and tire size, as the .70 overdrive on the 700R4 is pretty tall?

 

[Clay]

Well, I guess that I'm not totally sure it isn't a t400. Honestly, I just figured it wasa 350. When I get home from working in Alaska in a couple weeks I'll have to look really hard at it. If it is, knowing what you know now, is there a better way?

I have 33" tires 4.10 gears in the axles. I don't have a tach, but I would guess the thing is running at 3000 rpm at 65, top speed is pretty much 75. A couple of those trips across the great salt flats on I-80 I could push it, but that was about the max.

How much of a mileage increase are you seeing since you swapped, if any? I'd like to get the van up over 10 mpg, and this along with skinnier tires and lowering it down a little makes the most sense.

Thanks again for the help.

 

[barefoot boy]

33's and 4.10 gears calculates as 2715 rpm at 65 mph. A 700R4 in 4th with the converter locked will be turning 1900 rpm at the same 65 mph. Mine also has 33" tires and 4.10 gears. I really do not know how much it helped my fuel mileage as I did the transmission swap right after I got the van and did not drive it enough with the TH400 to establish fuel mileage. I do know it is much quieter to drive at 65+ with the OD transmission. I do not calculate my fuel mileage, but these big vans are not going to get a whole bunch better than 10-12 mpg in my opinion.

 

[k9lestat]

Lol I'm lucky to get that in my suburban

 

[Clay]

That's an interesting calculation. I will add a tachometer to the mix here in the rebuild, it's a nice thing to have.

Noise reduction is definitely a concern. I've been reading quite a bit about different ways to do it and haven't quite decided which is best at this point. I know that insulation is a big part of it, but ditching the loud mufflers, killing wind noise and replacing the seals around the dog house are going to help just as much. You are right about the lower rpms better for noise, I didn't think about that part of it.

10-12 mpg would be OK, since its getting more like 7-8 at this point. Anything will make it better.

 

[mgmetalworks]

Well, I guess that I'm not totally sure it isn't a t400. Honestly, I just figured it wasa 350. When I get home from working in Alaska in a couple weeks I'll have to look really hard at it. If it is, knowing what you know now, is there a better way?

TH400 and TH350 are easy to tell apart.... The TH400 has an oil pan that is shaped a little like Texas. The TH350 pan is a square with one chamfered corner.

 

[Clay]

Thanks for the picture. That's a good one for the archive.

Mine is a 350, and I had forgotten that it even said that one the tag under the hood.

 

[Clay]

Wiring upgrades

The only progress I have so far, is that I rebuilt the carbuerator. Rebuilding the edelbrock was actually pretty easy. Since the van sits for so much of the year, while I'm at sea, I need to come up with a way to get the fuel out of the carb while I'm gone. I'm thinking about just using a cut off switch on the fuel line and running it dry, but I'm not sure this is ok to do.

I'm thinking about doing some serious wiring work on the interior of the van here soon and I wanted to ask some questions for those in the know.

First up, the wipers not having an intermittent setting drives me crazy. Can I swap one of these?

http://pages.ebay.com/link/?nav=item.view&alt=web&id=301268256700

NOS GM Delco 1977 Chevrolet Truck Van G-Series Intermittent Pulse Wiper Switch

Pricey, but if it works I would pay for it because I don't want to clutter the dash with cheap junk and factory stuff is usually better anyways.

When I re-do my house batteries I want to run everything through a fuse panel or block of some type. I'm thinking about something like this:

https://www.bluesea.com/products/5026/ST_Blade_Fuse_Block_-_12_Circuits_with_Negative_Bus_and_Cover

Anyone have any ideas or thoughts on it including other suggestions?

One other question, all of my interior lights are garbage and I want to wire up some LED's. What have you guys used for reading and overhead lights?

I'm busy stacking up parts (and sea time to pay for it all), but when I get home soon I should have some good updates for the thread.

 

[Clay]

First up, the wipers not having an intermittent setting drives me crazy. Can I swap one of these?

http://pages.ebay.com/link/?nav=item.view&alt=web&id=301268256700

NOS GM Delco 1977 Chevrolet Truck Van G-Series Intermittent Pulse Wiper Switch

Pricey, but if it works I would pay for it because I don't want to clutter the dash with cheap junk and factory stuff is usually better anyways.
.

NEVER MIND on this! I was reading through the service manual and found that there is three parts to that system. The switch, the motor and the pulse controller. All that is probably too rich for my blood.

Does anyone have a solid way to accomplish this with good aftermarket parts?

 

[barefoot boy]

You might be able to swap in a later model steering column with the single stalk wiper/headlight dimmer switch. My '88 van did not have tilt wheel/ intermittent wipers, and I swapped in a column from my '87 parts van. Chevrolets are pretty good about letting you swap stuff from year to year.

 

[Clay]

Well, I burned up some satellite Internet minutes last night and found out that this is totally possible. It's just a plug and play module and switch that gets replaced.

Switch:

http://www.brotherstrucks.com/prodinfo.asp?number=WWS083P

http://www.classicparts.com/mobile/1978-83-Windshield-Wiper-Switch/productinfo/67-656B/#.VERsR9m9LTo

Module:
http://www.classicparts.com/mobile/...ntrol-Module/productinfo/67-682/#.VEUWotm9Kc0

I ordered them up, let's see just how easy it is!

 

[Clay]

Now, I have a sliding door and it's not ideal, but I don't always have love for it. There are times when I wish I could make it swing instead. After searching, I found this and wanted to see if anyone had ideas about it.



Here's the link to the build thread:

http://www.vanning.com/threads/ubbthreads.php/topics/662860/5

So, good or bad?

 

[Eric3187]

that door is pretty cool! the downside(s) i can see is that you have to make sure you have enough room to open it otherwise its completely useless. Also, if the struts start to fail, you have to muscle the door open and stick a rod in there to keep it propped up.

 

[k9lestat]

i talked to a guy who did a similar mod. he used a piano type hinge and the pneumatic struts. also did the rear doors like that. i forget which forum it was.

 

[Clay]

Did he like it over time?

I found a video of a van that appears to have this mod on the back doors, which seems more practical in some ways.

I don't really mind the slider personally, my only complaint is that it's noisy and hard to sneak out in the morning after camping out to make coffee or whatever.

I would like to modify the rear doors so that they can be opened from the inside, but I'm still working on how to do that.