Introduction and help needed: 1988 6.5 Suburban

[AugustDiesel]

Hello all,

I had posted a while back in the 6.5 turbo forum but perhaps I may be better suited here since the engine I have is not a turbo, but an NA 6.5 goodwrench warranty engine.

In my last post, I had discussed a severe leak from the 4x4 700r4 transmission when in reverse. I have since found out that the case was cracked. Ended up replacing the transmission with a beefed up and rebuilt 700r4 and all seems to be doing well. Which brings me to my current question:

My transmission cooler lines are worn out. Corroded, rusty, cracked in some places thereby leading to rubber hose patches that I'm not all that confident in. I want to replace them and LMC Truck sells prebent transmission cooler lines, however, they have two different part numbers, both of which are applicable to my situation:

34-5718: 4x4 Diesel
34-5719: 4x4 TH700R4

As you can see, both are applicable as I have both a Diesel engine and a TH700R4. The truck was originally a 6.2 diesel from the factory so I don't think having a 6.5 makes a difference.

Anyone have any ideas on which is the correct part number?

Here is a current pic of the truck. It's a project for sure, and needs a lot of work, but is coming along:

3497

[trbankii]

In your situation, I’d check with LMC. They’ve been very helpful when I’ve had questions about their products.

[AugustDiesel]

In your situation, I’d check with LMC. They’ve been very helpful when I’ve had questions about their products.

Thanks for your quick response. I forgot to mention that I actually did call LMC first and the lady I spoke to said to ask a mechanic because they would not be able to advise me. So I figured I'd start here since this forum is 6.2/6.5 specific.

[DmaxMaverick]

If a supplier offers multiple products for one application, it is their responsibility to describe the difference(s). If they don't, then they don't deserve your business. I've had many contacts and purchases from them, and never experienced that attitude. I suggest another call. Your mechanic can't determine what LMC's products will fit without a proper product description and fitment advise. For a customer service rep. to suggest otherwise is ridiculous.

[trbankii]

Totally agree with DMax. Any mechanic is going to say the same thing you are - it’s a diesel AND it has a TH700R4, what are the differences in the two products you are providing?

[AugustDiesel]

I agree with you both. I did call a second time and got a different lady who said they are not able to give technical advice, but, she did look through the catalog with me and she thinks it may be the 35-5719 for the 700R4 but still is not sure. At least she didn't blow me off like th first lady did. Still don't want to place the order until I know I'm getting the right part. Perhaps I should look at building my own lines from stainless steel hose or something? Wish I could get through to someone at LMC with some technical knowledge but I keep getting these reps who only know what their computer screen is telling them.

[DmaxMaverick]

IF the only specifications for the kits are "Diesel", or "700R4", then definitely get the "700R4". There were other tranny options (5-speed, TH400) for the model/year, so that will be the most important. The "Diesel" specification is less important, only because the radiators are different. The fittings will be the same, but will not be in the same location. The lines can be modified to fit the radiator (bend, or cut/splice with hose section), but less likely with a different tranny.

If you do need to cut/splice with a section of hose, use a flaring tool to slightly flare the ends (debur and flush!), AND use double clamps (4 clamps per hose section, 2 on each line connection). It will leak and/or blow off if you don't. Be sure to use specifically labeled heavy duty ATF hose. None other.

[trbankii]

That’s crazy… It’s not like you’re looking for technical specifications or engineering info - just basic fitment. Does it fit THIS or does it fit THAT?

I thought they had an order line and then another number, but I just looked at their website and there are just the toll-free and the local numbers. I’m not sure if the local number connects you with someone different? You could also try sending them an email - CustomerCare@LongMotor.net

[AugustDiesel]

Yep, found the email address and sent them an email detailing the problem and concern and asking for a guided response so that I can make an informed decision. We will see if that produces any better results. Depending on their response, if I get a response, I'll order the part number for a 700R4, as you recommended DMAX, and proceed from there. Will keep y'all posted! Just trying to prevent a future failure and a breakdown.

[AugustDiesel]

Seems as though the email produced positive results! I got a quick response thanking me for contacting them and asking for the Vin number of my truck and some other specific information so that they can try and do a stock match. I provided them with as much info as I could and photos of the transmission lines and where they plugged in and they will forward that information to their quality control department to try and do the stock match. We will see what happens.

[trbankii]

I’m glad you finally got a response from them. It just seemed crazy that it was up to you (or your mechanic) to decide which of their products would work.

[AugustDiesel]

Yeah hopefully they'll be able to find me something. I've already got several patches in these lines and now it's leaking at the transmission end.

[Robyn]

Reading this thread through and HMMMMM

If it were me I would scare up some suitable hydraulic hose (Fabric outer with steel cladding over the inner core)

The reusable type like Aeroquip that accepts the hand tool installed fittings.

Route the lines from the radiator back keeping then away from the exhaust and then secure them accordingly.

This type hose is very affordable, quite durable and you will not deal with issues.

Napa stores carry it and the fittings.

The fittings are normally a standard J I C type taper seat and can readily adapt to the radiator and tranny.

Easy, safe and even a tad over kill.

If you really want overkill you can go with stainless braid covered hose.

The trans cooler line pressure is very low so the hydraulic hose is far more than enough.

Just be sure you use a large enough size as not to CHOKE the flow

Just sayin :)

[JeepSJ]

Bowtie Overdrives also has a nice kit for semi-fabbing your own. They come with pre-bent lines that go from the trans up to the front of the engine, then braided and fittings for you to route your final plumbing up to your radiator. Worked great with my 6.5/700 combo.

Here is the side-tank version -
http://www.bowtieoverdrives.com/catalog/catalog_inc/viewitem.php?ITEMID=283

They also have a bottom-tank version.

[AugustDiesel]

Finally heard back from LMC and long story short, they don't have a part for my application. So on to other alternatives.

[AugustDiesel]

Update: so I was hoping to deal with this before a failure happened, but the failure beat me to it. One of the rubber patches split last night. At the very least, it waited until I got home and was parking the truck. I think I am going to use hard line and bend them where I need them to go.

Question for you all: after all my experiences with this, I am very interested in installing a transmission pressure gauge so I can monitor for future failures. I can't seem to find many kits for this. Do y'all know of any or would it use the same parts as an engine oil pressure gauge/switch?

[DmaxMaverick]

IF the only specifications for the kits are "Diesel", or "700R4", then definitely get the "700R4". There were other tranny options (5-speed, TH400) for the model/year, so that will be the most important. The "Diesel" specification is less important, only because the radiators are different. The fittings will be the same, but will not be in the same location. The lines can be modified to fit the radiator (bend, or cut/splice with hose section), but less likely with a different tranny.

If you do need to cut/splice with a section of hose, use a flaring tool to slightly flare the ends (debur and flush!), AND use double clamps (4 clamps per hose section, 2 on each line connection). It will leak and/or blow off if you don't. Be sure to use specifically labeled heavy duty ATF hose. None other.

As suggested before, this may be the best/easiest option. You can source stock tubing and bend it (not as easy as it sounds, unless you have experience do this), but that also requires adapting fittings. If the "kit" fits the tranny and chassis, that will get the lines to the radiator. The Diesel radiator will be different than a gasser, but getting the lines to that point will save a LOT of work and grief.

If you do bend the lines, use a tubing bender of the correct size and radius for your intent. I have extensive experience fabricating hydraulic lines (military aircraft and heavy equipment), and it is not easy for a novice, even with an original (failed) line in hand. I was REALLY good at it, but it took years of mistakes to get there.

In regards to the pressure gage, the line pressure at the coolant circuit is low (no more than engine oil). However, the internal circuit pressure in the 700R4 can peak at 400 PSI (compared to 90 PSI of the TH350/400). Be careful where you tap for your gage. A simple Tee into the cooling return line may be the best option. It's been many years since I've been up to the elbows in a 700R4, so there may be a better option, but I don't remember. I'll bet Robyn could tell you....

[AugustDiesel]

As suggested before, this may be the best/easiest option. You can source stock tubing and bend it (not as easy as it sounds, unless you have experience do this), but that also requires adapting fittings. If the "kit" fits the tranny and chassis, that will get the lines to the radiator. The Diesel radiator will be different than a gasser, but getting the lines to that point will save a LOT of work and grief.

If you do bend the lines, use a tubing bender of the correct size and radius for your intent. I have extensive experience fabricating hydraulic lines (military aircraft and heavy equipment), and it is not easy for a novice, even with an original (failed) line in hand. I was REALLY good at it, but it took years of mistakes to get there.

In regards to the pressure gage, the line pressure at the coolant circuit is low (no more than engine oil). However, the internal circuit pressure in the 700R4 can peak at 400 PSI (compared to 90 PSI of the TH350/400). Be careful where you tap for your gage. A simple Tee into the cooling return line may be the best option. It's been many years since I've been up to the elbows in a 700R4, so there may be a better option, but I don't remember. I'll bet Robyn could tell you....

Thanks DMAX, I certainly prefer to do an inline setup at the cooling return line, as you prescribed, rather than tapping into the trans case, for the pressure gauge. I simply want to monitor future trans line failures via a method other than the "I smell transmission fluid" test!

[AugustDiesel]

Planning out how to route these lines. Hoping to get it done on Wednesday. Anybody ever route the lines over the top of the transmission to get them to the drivers side and then up the frame rail to the radiator? There's lots of space above the tranny and would keep the lines far away from the exhaust pipes. Due to the direction of the inlet/outlet the lines would have to do an immediate u-turn to go over the top of the transmission. What do y'all think?3522