I am not happy with my underbelly

[1leglance]

Ok so I have a new to me 1970 3/4ton 4x4 Suburban that I know the previous owner put a crate motor in.
It also looks like a Turbo 400 was added as that is what I remember this trans pan looking like.


It is connected to this transfer case (I have no idea what this is...any help?)


And it all hang down really really low with what look like spacer blocks making it even lower.








So while my front driveshaft seems well lined up I am not happy about how low all this hangs under the rig.

I questions are:
What is this transfer case?
Can I move it up at all?
Can I custom make a thinner crossmember and gain some clearance? I would be adding skid plates at the same time.
What are the thoughts of the wise ones around here?

Thanks in advance...I am not a rock crawler but since my family like to do remote travel for many many days far from help here in the desert southwest I don't like things being low & ready to be bashed

['63GENIII]

I think what you have there is the desireable NP205.
I'm wondering why the trans and TC were lowered? Clearance issues (trans hump or exhaust?) or maybe driveline angles. Whatever it is, it looks like you could potentially get that crossmember back up on top of the lower frame rail and get back close to 3" of clearance that was lost. If the th400 hit the floor, I would think it possible to get a new trans tunnel to give it more room. If it was the driveshaft angles, I would get the pinion angles set correctly and then get the right driveshafts built for it (youre not running a huge lift). In your last photo, I believe the two bushings are supposed to sit on top of the "frame bracket" and that the crossmember that is hanging from that bracket is actually supposed to sit on top of the bushings. It also looks as if the exhaust could be routed under the crossmember as well. I'm not sure if there were ever any TC skid plates made for chevys but you could always fab up some sliders to protect the case and trans. Cool truck and cool trip!

[special-K]

That Suburban must have been lifted at one time. Those Transfer case spacers can go. I've never used them even on a 6" lift. You probably could make a crossmember slightly higher. I know there are companies that make tubular once to gain slightly better clearance.

[1leglance]

I will take a pic of the inside as I am not sure if I have the high hump or low hump trans tunnel

[Stocker]

From a recent thread:

Originally Posted by gofast68c20

High tunnels bolt in and the lows are part of the floor.

Originally Posted by vectorit

"High hump"

And finally, this from Andy (Longhorn Man) on which trucks came with high humps:

Originally Posted by Longhorn Man

all 4x4
all 4 speeds (regardless of motor)
Big block/auto.

Small block or inline with TH400 did not require high hump floors

[DirtyLarry]

Lance,

You have some good hardware there. This era of 4x4 Suburban didn’t come with TH400 transmissions so someone swapped that in. In fact, they swapped in the front driveshaft, tcase and crossmember as well. All of those pieces are from a newer truck. Looks like late 70’s maybe even 80’s square body style pieces. Aside from the shape of the crossmember the fastening method the front drive shaft to the 205 is also the telltail sign of later model pieces. The early 205’s had a small yoke like the rear yoke opposed to the large round ring. I am running a 1972 tcase so if you look at pictures of my front yoke you will see what I am talking about.

Being the person that swapped this in used a newer crossmember is probably why they added the spacer between the crossmember and frame so things would line up. Looks like a pretty clean install so I wouldn’t mess with it if you don’t have any vibration issues. Not sure what that wire connector is on the back of the tcase.

Two recommendations:
1) Get rid of those headers and go back to exhaust manifolds. For the small amount of power gained from headers isn’t worth the hassles of exhaust leaks and starter motor issues. (you can lay those headers next to your carburator in the scrap pile after you do the TBI swap )
2) remove the tcase to frame rail support bracket. Those are bad! We just had a long conversation about those here after I spoke with one of my old GM engineer buddies.

[1leglance]

Thanks for the pic & info Stocker....I very much have a high hump, wow typing that sounds so dirty

Larry...I am already shopping for Ram Horn stock manifolds as I have lots too many starters over the years and hate how low they hang.

I will read the link you gave on the transfer case bracket.

My real concern is just how low everything is...anything I can do to tuck things up a bit before I skid plate it all?
There seems to be room above the trans to lift everything at least 1-2in.
The breakover on these long wheelbases is brutal and I would like as much clearance as possible. Again I am not a rock crawler but I do find myself in a pickle now & then.

Glad to hear the drive train is good.
Down the road I will be thinking overdrive trans (700R4?) vs gear vendors overdrive....since we all know how much highway we do getting to the cool dirt places.

Oh and I just installed my craigslist Holley Off Road Avenger Carb and tuned it with my old Vacuum Gauge so we will see how long till I start picking your brain on TBI Larry

[DirtyLarry]

Yeah, that is the bad thing about that style of transmission crossmember, it does hang low. I don’t recall if that design xmember had provisions for skid plates or not.

One option would be to get a trans xmember, skid plate xmember and skid plate from a early to mid 70’s truck like the ones below. Then you could get rid of those homemade spacers too.

This is the stock transmission xmembers and skid plate on my dad’s ’78 K20. Automatic and manual xmembers were the same if I recall correctly.


My blue K10 truck. These are ’76 xmembers, ’72 tcase and 2006 transmission. You’ve seen it. It doesn’t hang low at all and the skid plate works well. Lots of scars on it to prove it. I think these are the same xmembers used on pre-73 K5 Blazers and 4x4 Suburbans



You can see from the pictures between what you have and my two 78's, there have been a few different looking xmembers used over the years in 4x4's.

[mosesburb]

I agree with Larry that your transfer case is newer, but I believe it to be an '85-'91 model because of the crossmember and the short adapter between the transmission and t/case. That being the case (anyone up for a pun??), you will not be able to use the early flat style crossmembers and skid plates because the transmission mount attaches to the adapter on both styles, but the one you have is very short compared to the ones in Larry's pictures. The tall adapter uses two mounts that consist of four pieces while your short adapter uses one simple mount. I'm going to venture a bet here that the crossmember spacers are there to get that bracket from the transfer case to the frame rail in the right place to bolt up. That is the only reason I can think of to have it there. An easy way to check is to pull the nuts off of the trans mount where they drop through the crossmember (also remove the frame bracket and throw it away) and use a block of wood under the pan and just jack it up and see if it goes up a little more than the thickness of those spacers. I bet it does and if that works you can just remove those spacers and bolt it directly to the frame rails.

As far as skid plates go, I know there was a skid plate available for the NP208 that used the same (or very similar) crossmember, but I am not positive that one was offered for a NP205. They were made of aluminum that was pressed, dimpled and shaped for strength, but it was still 3/16" or maybe 1/4" thick (at most) aluminum. That crossmember shape lends itself well to fabbing one of your own. Look toward the end of my thread and you can see the one I made. It is similar to something that could be made for this style crossmember. Now you could make it out of something lighter than 1/2" plate, but the basic idea would work well.

[DirtyLarry]

Mosusburb,

You’re absolutely correct. I just looked under my ’89 Suburban and Lance’s xmember is identical to mine. In his case, (pun again ) that would mean he also has the desirable round pattern 32 spline 205! Good score Lance! I looked high and low for one of those last winter when I did my NV4500 swap.

BTW I was looking through your thread the other day. Great job on your Suburban! Nice to see another old GM truck out on the trails! Maybe we can all met up in Northern AZ or Southern UT sometime.

Bone stock ’89 V2500 Suburban with SM465/NP241


Looks like my xmember took a good whack at least once right under the driveshaft I just picked this rig up a few weeks ago and haven't crawled around under it much. Getting ready to yank it apart to install a new clutch in a couple weeks though.


SM465 to 241 adapter. Different beast than a TH400 but still very similar. I didn’t realize the round adapters were shorter but they certainly look like it compared to the old style on my K10.

[1leglance]

Ok so on craigslist is a 700r4 out of a 90's 4x4 and the price seems decent.
I have been reading the threads on swapping in a 700r4 and they all seems to refer to replacing the Turbo350 and talk about a 2wd 700r4.
I understand about the Advance Adapter output shaft on that conversion but not sure how it applies to me.
I really love my BowTie Overdrives 700r4 behind my RamJet 350 in my 72 C-10 long bed street truck. It would be really nice to the better mpg from the overdrive but not sure what all I will be up against on the conversion.

More than likely if I do the 700r4 then I would look at making my own crossmember that tucks up a bit more then building my own skid plates that also protect the transmission & oil pan.

Overall my goal is NOT to do much of a lift, for daily driving & camping I prefer NOT to have much of a lift. So that means better belly protection since I won't be as high in the air.

Keep all the great comments coming guys and I am learning a ton.

Oh and Larry yes we need to do a post Overland Expo trip as I am taking the week after the event off work.

[mosesburb]

There is going to be quite a bit more to this than just a trans swap. Right now you have the best combination of simple and bombproof in one nice package. I understand your desire for lower engine speed while cruising and some more mileage, but at the same time the durability of your current setup should not be overlooked. Lower engine speed while cruising on the highway. There is no debating this. Overdrive will lower engine speed on the highway. Fuel efficiency; a 700R4 will *probably* net you a slight (and I do mean slight) increase in mileage. This is good especially with the price of fuel now and foreseeable future.

Now, on to the needs of the swap. Your transfer case will not work with the 700, so you will need to obtain a different one and probably have to go through it as it is an unknown item. You could choose a different transfer case while you are doing this. I may ruffle some feathers with this next statement, but if it were mine, I would go with a NP241. It is lighter than the 205 and has a much better low range (2.72:1 in the 241 vs. 1.96:1 in the 205). It doesn't seem like much difference numerically, but it makes a world of difference on the trail--especially when coupled with the 3.06:1 first gear of the 700 (vs the 2.48 of your TH400). The 700R4/NP241 is known as the poor man's doubler because the combo has a great crawl ratio. The biggest con to the NP241 is that it has a slip yoke rear output. That is bad. It requires a slip yoke eliminator. That is expensive. You would need the part ending in 1950 HERE. The nice thing about this swap is it does not require a teardown of the trans to change the output shaft so money saved there. Also, the NP241 cases typically don't bring the money that a NP205 brings. Possible savings there. There is also a conversion output shaft for a 700R4 to convert it to a 32 spline shaft like the 400 has and also an adapter to convert the four bolt square bolt pattern of the 700 to the six bolt flange of the 400 Info HERE. That's a bunch of money, but it may save some in the end. I do not know what this does for the overall length of the trans, so I don't know if it gets longer or shorter or stays the same. Keep in mine if the transfer case moves forward OR backwards you have to have two driveshafts modified. The one that gets shortened will be fairly cheap. The one that gets lengthened is going to be money. A chunk of DOM tubing is cubic dollars these days so calculating overall lengths of the trans/t/case will be a very good investment of time.

The other obvious option is to go with another NP205. You need to find ne from a TH350 and the adapter. This is a pretty straight forward deal. NP205 = bombproof. This is good. The one you find will probably need some work. Plan on at least a seal kit for it. Not big money, just time to clean the typical NP205 funk off of it and replace some seals. Even a bearing kit is not too bad pricewise. Plan on buying a coupler for the input shaft to the output shaft of the 700R4. Last time I sold one I *think* it was around $120 or so. I could be wrong on the price though. These wear out over time and you don't want to put a worn one on a new Advance Adapter shaft. The NP205 swap will require a new cross member as it will use the "tall" adapter. I have some of these, and skid plates, and skid plate cross members so no cost there.

The trans will bolt to the motor and flywheel with no problem. The TV cable on the trans (kickdown looking cable) is a very finicky and tremendously vital component that absolutely must be geometrically correct for long transmission life. You are dealing with a non-stock application with a non-stock carb setup which can be difficult to setup correctly (the possibility does exist that it will adjust up with no problems--this possibility does not exist with my luck). This trans also needs a large cooler for obvious reasons as well as the lockup converter diverts some fluid from cooling to lock the converter.

So, with all of this info, a strategy will have to be planned to figure out what method will result in the best combination with the least investment of time and money. Also, while calculating your costs figure the time and miles it will take to repay its cost in fuel savings. I'd figure *maybe* 2mpg savings. There are many variables (more than I have listed) to consider as to what will end up best. *Author opinion time* If it was mine and I had the TH400/NP205 setup you have, I would worship it and not change it. The 700R4 is an inferior transmission in almost every way when compared to a TH400. The only thing a 400 loses to a 700R4 is it doesn't have O/D. I know the 700 can be built to handle whatever and be made strong and blah, blah, blah. Everyone I know that had a built 700R4 in their rig got sick of repeatedly blowing it up and swapped it out for either a manual or a TH400. I know there are plenty out there that have had success with them, but I don't like them in heavy trucks like ours *just my opinion though*.

So if it was mine, what would I do?? I'd leave the trans alone and I'd inject it. I know you have expressed reluctance toward this idea, but that is what I would do. You may experience some mileage increase, but your drivability will increase greatly--especially at altitude!! It is almost impossible to tune a carburetor for good performance at low AND high altitude. A happy medium can somewhat be achieved, but a TBI unit adjusts automatically. Figure out what you are looking at price-wise to swap in the light-duty 700R4 and then take a look at a harness from Howell and a TBI setup off of craigslist or a wrecking yard. I have some parts but the basics will be needed. You can also swap to a 31 gallon tank like I have or possibly a 41 out of a Suburban. In the end, I think this would serve you better--*/opinion*.

Now, if you really want mileage swap in a 6.2L diesel. Seriously. I have to change my previous statement. If I had your trans setup, I'd put a 6.2L diesel in it. Ok, I'm done now.

[mosesburb]

Originally Posted by DirtyLarry

BTW I was looking through your thread the other day. Great job on your Suburban! Nice to see another old GM truck out on the trails! Maybe we can all met up in Northern AZ or Southern UT sometime.

Thanks!! Your setup is pretty amazing. I really dig that camper you had built. Very cool.

Yeah, anybody can run the new stuff on the trails, but that just ain't my style. It would be cool to meet up and run some trails with you.

[DirtyLarry]

I totally agree with Mosesburb on this one as well, even down the 6.2L swap. I too would initially put money towards modernizing the engine that is in it now with EFI than worry about a costly trans swap (downgrade to 700R4). A simple TBI EFI swap would address fuel economy to some degree, performance and drivability concerns in one upgrade. I also noticed in the pictures on Expo your Sub still has breaker point ignition too! Ah, man….that is another fine item to toss in the trash right next to the headers and carburetor! You could kill several birds with one stone by doing a TBI swap (and HEI).

Get the TBI goodies and come up here. Billy and I will knock that out in a weekend! Probably quicker than the bumper build on the Troopie.

[1leglance]

You guys are killing me with all the great info...
I think I like the sound of driving it for a while and seeing what my real world mpg on the highway & the trail is then moving forward with some changes.

My wife is the office manager of a diesel engine shop (they weld broken heads & blocks up) so if I go diesel I have lots of options on building anything I want to drop in.

I really need to get the interior worked out before I do any more drivetrain stuff. Camping and playing in the dirt is goal #1 so I want to limit downtime from swapping parts.

Larry I hear ya on the TBI & I have been reading threads. I really see where you are coming from.

Great info guys and I can't thank you enough....now to shop craigslist for welder so I can get started on the aux battery tray, bucket seat frames, on board air brackets, roof rack and so much more.