Quandry on NP208C1 in 1988 Suburban V10

[ballencd]

Guys,

I am new the community and new to my Suburban and have a question....or several.

My 1988 V10 Suburban...5.7/TH700R4/NP208C1.....had/has a speedo issue. I ordered what I thought were the right gears for it since when I pulled them they were stripped both inside and out. I am thinking I got the gears for the 2WD TH700R4 and not the NP208 output but that is another issue.

After rebuilding the rear brakes I drove it and it seemed to be running hot...gauge is working and the temp stayed at normal temp....about 180 but the engine compartment seemed hotter then it should be after a drive. I found thru research here that the speedo (gears stripped) sends a VSS signal to the computer which could cause hot engine and trans.

My question: When I drained the transfer case I only got about 3/4 of a pint....yes pint of fluid. I can seen some of the inside with the tail piece off and don't see any damage...i.e. metal, discoloration, broken parts but am wondering what I should do with it at this point....disassemble/inspect and rebuild or put it back together with the correct amount of oil and see what it does? How hard are they to rebuild...i.e. can I do it at home? I am handy with tools but have not a lot of experience playing with transmission type stuff..

Charlie

[truckster]

First of all, you know the 5.7 is a V8, not a V10, right?

What do the seals look like? The transfer case isn't terribly complicated, but I would recommend having a transmission jack to remove it. A good helper wouldn't hurt, either.

Gear oil isn't all that expensive, so you might just full it and see if it's got any major leaks. With a 25 year old vehicle, a small leak over time could be the cause of it being so low, or it could have a major leak. If you do have leaking seals, make sure you look for damage on the yoke/shaft that runs through the seal. If the metal is worn, you'll have to replace or sleeve it before you'll be able to get it to seal.

[Captainfab]

I believe he is referring to the series designation for his Suburban. In 1987 the series designations changed from the C and K series, to the R and V series, for the '87 pickup and the '87-'91 Suburbans, Blazers and Crewcabs. His '88 Suburban is a V series, being a 4wd, but should actually be a V1500 instead of a V10.

Originally Posted by truckster

First of all, you know the 5.7 is a V8, not a V10, right?

To the OP. If the transfer case was not making any noises previously, I would go ahead and change the speedo gears, and refill with the correct oil, and see what happens. I assume you have checked the VSS and speedo cable to be sure they are not bound up?

[ballencd]

Thanks for the update. The case was noisy in 4wd before but not in 2wd. Since I could not see any problems and there was no metal in the bottom I decided to try it as suggested. I had verified that the speedo was free prior to ordering the speedo gears and tested with my drill in reverse. Turns out I got the wrong drive gear (i suspect the one for the 2wd model) Upon inspection of the existing gear it was chewed up on one end of the gear only...just past the middle...see prior post picture...so I cleaned the gear I had with a x-acto knife and turned the gear around to move the good part of the gear to the right location and put it all back together and tested it. The speedo works now, no apparent leaks, but I will keep an eye on it. The 4wd is not as noisy as it was before. I have to work on the VSS testing, OD lockup testing and cruise control testing still. I will pull the driven speedo gear in a few days and verify it is not wearing abnormally.

The V10/20/30 designation is correct for Chevy...Chevy and GMC switched the K/C designation to V/R for the 1987-1991 year models for the Suburban/Blazer/Jimmy vehicles....Chevy used the older 10/20/30 and GMC used the newer 1500/2500/3500.

Thanks for the help.

Charlie
Posted via Mobile Device

[ballencd]

Guys....the speedo has been working and pretty accurately also....with no abnormal wear yet to the new gear...although I have not driven it very far yet! Thanks for the help.

I still have two questions I hope someone can answer...???

1) How do I test for lockup on the TC? I do not have a tach yet on the vehicle.
2) The Suburban has a large gas gauge on the right of the speedo....is there a way to change it out so I have a small gas gauge below the volts gauge which is empty now and add a factory tach to the current gas gaugh location using factory GM gauges? The wiring I can handle but will the gauges fit?
Thanks

Charlie

[ballencd]

Hello, back again. Speedo has been working fine since my last post. Yea!

I still am looking for answers to:

1) The tach question...can I either put a instrument cluster from a car with factory tach in this suburban (1988 V10 Suburban) and have it work or can I remove the factory gas gauge and put in a factory tach in that location and also install the smaller factory gas gauge in the empty hole....also installing the cluster circuit board from a vehicle with a tach? Inquiring minds want to know.

2)How do I test the tcc lockup without a tach? Does this vehicle lockup in any other gear then OD?

Thanks

Charlie

[b454rat]

AS for the tach, you can plug n play with a cluster from an 80 or newer. You'll have to swap your existing speedo, but will bolt in with no mods. The circuit boards are different between tach and non tach, so simply putting one in won't work.

[ballencd]

B454rat,

So you are saying I can get a 80-newer cluster with a tach, swap out the speedo (since I want it to be correct) and install the cluster and it will work with no mods to the wiring harness for the tach or the gas guage in a different location? If that is what you are saying then that would be great. I was thinking about nearly the same but installing a small gas gauge and tack in my cluster with a cluster circuit board made for a tach console but your route would probably be cheaper and easier in the long run.

I have read so stuff on the TCC and seems like a tach would indicate that it was locking...that is what I am hoping anyway.

Thanks for the reply. I am loving the V10 but it still needs a few fixes and tweaks to get it right.

Charlie

[b454rat]

I did this to an 87. I found a cluster from a 78 I think, checked the plug that they were the same, swapped my speedo into the tach cluster, got a white faced overlay (79 older are different font than 80 and newer), and plugged it in. The speedo worked since it was the one that came out of the truck, the tach worked, and so did the rest of the gauges. Everything worked as it should, like it was factory. Wiring the tach is simple...

[ballencd]

Thanks B454rat, I will start looking for a cluster!