89 GMC Cummins conversion - Page 7 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

COS399 · 07-07-2014, 11:24 AM

Yesterday I drove it on a 220 mile trip and after about 70 miles noticed that the transmission temperature was creeping up above 200 and finally settled in at 215. So I bypassed the thermostat switch on the trans cooler, added nearly two quarts of ATF and I am pretty sure that the ATF is leaking into the transfer case because there are no oil leaks. On the way home it stayed at about 185 degrees.

Hankster · 07-07-2014, 08:13 PM

Uh oh.. I'm not real good with tansmission or transfercases.. but that can't be good?

MTCK · 07-07-2014, 08:19 PM

That's a bummer. I didn't know the transmission had a thermostat... Guess I had better get educated.

COS399 · 07-07-2014, 08:59 PM

Quote:

Originally Posted by Hankster

Uh oh.. I'm not real good with tansmission or transfercases.. but that can't be good?

I think it will be more labor than parts.

Quote:

Originally Posted by MTCK

That's a bummer. I didn't know the transmission had a thermostat... Guess I had better get educated.

The aftermarket transmission cooler mounted up front has a thermostat that turns the cooling fan on and off, not the transmission.

COS399 · 07-07-2014, 09:22 PM

I found the installation instructions for the B&M trans cooler and the instructions show that the fan is suppose to come on at 176 degrees F (+ or - 5.4 F) and turn off at 140 degrees F (+ or - 5.4 F). I don't think that this is accurate but the next time I take it out I will take my infrared thermometer and check.

MTCK · 07-08-2014, 01:31 AM

Oh that makes sense. I was thinking a thermostat like restricting flow...

ryanroo · 07-08-2014, 07:21 AM

That sucks. at least the input shaft seals on the t-case are pretty easy to do. the de-bug process can be a patience tester for sure.

COS399 · 07-08-2014, 08:13 PM

Quote:

Originally Posted by ryanroo

That sucks. at least the input shaft seals on the t-case are pretty easy to do. the de-bug process can be a patience tester for sure.

hopefully you will be doing some shake down runs soon. That oil pan is killer!

COS399 · 09-13-2014, 10:24 PM

Not much to report. I have just been occasionally driving the truck around town and to work, which is just one mile away, to keep the batteries charged . I will probably be dropping the transfer case and resealing it after the kid is done with football, basketball jamboree, and the hunting season is over. I sold his 1978 CCLB K35 the other day so I will definitely be giving him this truck. He will barely be 14 this December so I am not planning on doing too much more to it until he is closer to getting his permit. Thanks for following along.

**Dieselwrencher** · 09-16-2014, 03:54 PM

I have to say that is a bad azz first truck. I hope I can do the same for my kids when the time comes. It's good to hear it's starting alright now too.

COS399 · 09-18-2014, 08:12 PM

Quote:

Originally Posted by Dieselwrencher

I have to say that is a bad azz first truck. I hope I can do the same for my kids when the time comes. It's good to hear it's starting alright now too.

Thanks Ryan. I'm sure you will have something nice for them. I only have one kid so getting him a vehicle is easier on the wallet. Yes, the truck has been starting right up and I sure am glad I found the problem. We need some updates on your project vehicles.

COS399 · 10-25-2014, 01:51 AM

Hoping to get a chance to work on transfer case seal this weekend to keep the transmission fluid from going into the transfer case.

COS399 · 11-30-2014, 01:57 AM

I still haven't changed my leaking seal and now the heater core has sprung a leak. I have been driving it a lot and I have to say that it does really well in the snow and on the icy roads. However, the mileage hasn't been that impressive.

MTCK · 11-30-2014, 02:20 AM

How good (bad) is the mileage? Glad you are getting some miles on her.

MTCK · 11-30-2014, 02:21 PM

That could be a lot worse! Winter just kills mileage. My tacoma gets down to just over 10 mpg sometimes if I'm abusing the auto start and it's really cold out. You're driving twice as much truck.

COS399 · 12-01-2014, 12:25 AM

i picked up a heater core yesterday and found some time to get it installed today. Now if I could only find the time to fix the seal. Maybe when Ryan is doing his northern tour he could swing by and fix it.

**Dieselwrencher** · 12-01-2014, 04:41 PM

Don't get too excited. I doubt that trip will be happening anytime soon.

72MARIO · 01-17-2015, 08:12 PM

Any updates i am curious how everything is holding up ? How about the mpg any better ?

COS399 · 01-18-2015, 02:04 PM

72MARIO - Thanks for asking but I haven't had any time to work on it. It will more than likely be a few months before I will get around to it.

I just got done watching the first episode of POWERNATION: Truck Tech involving the installation of a LBZ Duramax and Allison combo in a 1987 C10 short bed.

COS399 · 01-26-2015, 02:06 AM

I know it's not a Chevy and it's not like I have a lot of spare time, but the price was right! That is probably how most of our projects get started. I may one day put it in the "Alternate Tinkering" section.

COS399 · 04-21-2016, 06:08 PM

Quote:

Originally Posted by 72MARIO

Any updates i am curious how everything is holding up ? How about the mpg any better ?

So today I took the red truck for a little drive and put about 140 miles on her. I checked the mileage and it was 12.5 mpg, but that includes a lot of idling and short trips while tweaking the transmission tune. On my trip today most of the driving was at 75-80 mph. I'm sure the mileage will go up some after I fix the problem with the 3rd to 4th gear shift. I have to say that I got a lot of thumbs up from drivers in the two little towns that I went through.

**Dieselwrencher** · 01-26-2015, 11:49 AM

That is in really nice shape. What are the plans for it?

84chevyguyid · 01-26-2015, 01:41 PM

I dont recognize the brand, what is it?

COS399 · 01-26-2015, 08:37 PM

Quote:

Originally Posted by Dieselwrencher

That is in really nice shape. What are the plans for it?

Don't really have any plans at the time. I like it the way it is right now.

Quote:

Originally Posted by 84chevyguyid

I dont recognize the brand, what is it?

It is an International.

My brother saw the picture and immediately thought of a 6bt conversion.

84chevyguyid · 01-26-2015, 09:43 PM

That would have been my guess, what year? Does it still run?

07-07-2014, 11:24 AM	#1
COS399 Registered User Join Date: Dec 2013 Location: Northern, MT Posts: 569	Re: 89 GMC Cummins conversion Yesterday I drove it on a 220 mile trip and after about 70 miles noticed that the transmission temperature was creeping up above 200 and finally settled in at 215. So I bypassed the thermostat switch on the trans cooler, added nearly two quarts of ATF and I am pretty sure that the ATF is leaking into the transfer case because there are no oil leaks. On the way home it stayed at about 185 degrees. __________________ 1987 GMC R2500 SC 454 T400 1988 Chevy R30 CC DRW 12 valve Cummins NV4500 GearVendors

07-07-2014, 08:13 PM	#2
Hankster Registered User Join Date: Jan 2013 Location: Nacogdoches, Texas Posts: 895	Re: 89 GMC Cummins conversion Uh oh.. I'm not real good with tansmission or transfercases.. but that can't be good? __________________ Current Build 89 s10 ecsb 2wd 4.3/700r4 50k OG Miles Instagram- shaggin_s10 '86 Chevrolet C10 Custom Deluxe - Gen V 454 - 4l80e - welded 12 bolt (Build thread: http://67-72chevytrucks.com/vboard/s...d.php?t=611611 ) SOLD

07-07-2014, 08:19 PM	#3
MTCK Registered User Join Date: Dec 2009 Location: Fairbanks, AK Posts: 1,830	Re: 89 GMC Cummins conversion That's a bummer. I didn't know the transmission had a thermostat... Guess I had better get educated. __________________ -Marcus 1991 V3500 L29 454 4L80E NP205 D60/14 Bolt 4.56's 1984 K30 292 TH400 NP205 D60/14 Bolt 4.56's flat bed 7'6" Meyer Plow 2022 Silverado 3500 L8T Project Daily Driver Project Heavy Hauler Project Plow Truck

07-07-2014, 09:22 PM	#5
COS399 Registered User Join Date: Dec 2013 Location: Northern, MT Posts: 569	Re: 89 GMC Cummins conversion I found the installation instructions for the B&M trans cooler and the instructions show that the fan is suppose to come on at 176 degrees F (+ or - 5.4 F) and turn off at 140 degrees F (+ or - 5.4 F). I don't think that this is accurate but the next time I take it out I will take my infrared thermometer and check. __________________ 1987 GMC R2500 SC 454 T400 1988 Chevy R30 CC DRW 12 valve Cummins NV4500 GearVendors

07-08-2014, 01:31 AM	#6
MTCK Registered User Join Date: Dec 2009 Location: Fairbanks, AK Posts: 1,830	Re: 89 GMC Cummins conversion Oh that makes sense. I was thinking a thermostat like restricting flow... __________________ -Marcus 1991 V3500 L29 454 4L80E NP205 D60/14 Bolt 4.56's 1984 K30 292 TH400 NP205 D60/14 Bolt 4.56's flat bed 7'6" Meyer Plow 2022 Silverado 3500 L8T Project Daily Driver Project Heavy Hauler Project Plow Truck

07-08-2014, 07:21 AM	#7
ryanroo Senior Member Join Date: Apr 2004 Location: sw colorado Posts: 2,720	Re: 89 GMC Cummins conversion That sucks. at least the input shaft seals on the t-case are pretty easy to do. the de-bug process can be a patience tester for sure. __________________ 72 K20 12v build 72 K20 "parts truck" A place for your diesel swap questions

09-13-2014, 10:24 PM	#9
COS399 Registered User Join Date: Dec 2013 Location: Northern, MT Posts: 569	Re: 89 GMC Cummins conversion Not much to report. I have just been occasionally driving the truck around town and to work, which is just one mile away, to keep the batteries charged . I will probably be dropping the transfer case and resealing it after the kid is done with football, basketball jamboree, and the hunting season is over. I sold his 1978 CCLB K35 the other day so I will definitely be giving him this truck. He will barely be 14 this December so I am not planning on doing too much more to it until he is closer to getting his permit. Thanks for following along. __________________ 1987 GMC R2500 SC 454 T400 1988 Chevy R30 CC DRW 12 valve Cummins NV4500 GearVendors Last edited by COS399; 09-13-2014 at 10:31 PM.

09-16-2014, 03:54 PM	#10
Dieselwrencher 6>8 Plugless........ Join Date: Sep 2007 Location: Prairie City, Ia Posts: 17,140	Re: 89 GMC Cummins conversion I have to say that is a bad azz first truck. I hope I can do the same for my kids when the time comes. It's good to hear it's starting alright now too. __________________ Ryan 1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread 1972 GMC Sierra Grande Longhorn 4x4 1972 Chevy Cheyenne Super K20 Long Step side tilt, tach, tow hooks, AC, 350 4 speed 1972 C10 Suburban Custom Deluxe 1969 Chevy milk truck 1971 Camaro RS 5.3 BTR STG3 Cam Super T10 1940 Ford 354 Hemi 46RH Ford 9" on air ride huge project *Tired of spark plugs? Check this out.*

10-25-2014, 01:51 AM	#12
COS399 Registered User Join Date: Dec 2013 Location: Northern, MT Posts: 569	Re: 89 GMC Cummins conversion Hoping to get a chance to work on transfer case seal this weekend to keep the transmission fluid from going into the transfer case. __________________ 1987 GMC R2500 SC 454 T400 1988 Chevy R30 CC DRW 12 valve Cummins NV4500 GearVendors

11-30-2014, 01:57 AM	#13
COS399 Registered User Join Date: Dec 2013 Location: Northern, MT Posts: 569	Re: 89 GMC Cummins conversion I still haven't changed my leaking seal and now the heater core has sprung a leak. I have been driving it a lot and I have to say that it does really well in the snow and on the icy roads. However, the mileage hasn't been that impressive. __________________ 1987 GMC R2500 SC 454 T400 1988 Chevy R30 CC DRW 12 valve Cummins NV4500 GearVendors

11-30-2014, 02:20 AM	#14
MTCK Registered User Join Date: Dec 2009 Location: Fairbanks, AK Posts: 1,830	Re: 89 GMC Cummins conversion How good (bad) is the mileage? Glad you are getting some miles on her. __________________ -Marcus 1991 V3500 L29 454 4L80E NP205 D60/14 Bolt 4.56's 1984 K30 292 TH400 NP205 D60/14 Bolt 4.56's flat bed 7'6" Meyer Plow 2022 Silverado 3500 L8T Project Daily Driver Project Heavy Hauler Project Plow Truck

11-30-2014, 02:21 PM	#15
MTCK Registered User Join Date: Dec 2009 Location: Fairbanks, AK Posts: 1,830	Re: 89 GMC Cummins conversion That could be a lot worse! Winter just kills mileage. My tacoma gets down to just over 10 mpg sometimes if I'm abusing the auto start and it's really cold out. You're driving twice as much truck. __________________ -Marcus 1991 V3500 L29 454 4L80E NP205 D60/14 Bolt 4.56's 1984 K30 292 TH400 NP205 D60/14 Bolt 4.56's flat bed 7'6" Meyer Plow 2022 Silverado 3500 L8T Project Daily Driver Project Heavy Hauler Project Plow Truck

12-01-2014, 12:25 AM	#16
COS399 Registered User Join Date: Dec 2013 Location: Northern, MT Posts: 569	Re: 89 GMC Cummins conversion i picked up a heater core yesterday and found some time to get it installed today. Now if I could only find the time to fix the seal. Maybe when Ryan is doing his northern tour he could swing by and fix it. __________________ 1987 GMC R2500 SC 454 T400 1988 Chevy R30 CC DRW 12 valve Cummins NV4500 GearVendors

12-01-2014, 04:41 PM	#17
Dieselwrencher 6>8 Plugless........ Join Date: Sep 2007 Location: Prairie City, Ia Posts: 17,140	Re: 89 GMC Cummins conversion Don't get too excited. I doubt that trip will be happening anytime soon. __________________ Ryan 1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread 1972 GMC Sierra Grande Longhorn 4x4 1972 Chevy Cheyenne Super K20 Long Step side tilt, tach, tow hooks, AC, 350 4 speed 1972 C10 Suburban Custom Deluxe 1969 Chevy milk truck 1971 Camaro RS 5.3 BTR STG3 Cam Super T10 1940 Ford 354 Hemi 46RH Ford 9" on air ride huge project *Tired of spark plugs? Check this out.*

01-17-2015, 08:12 PM	#18
72MARIO Registered User Join Date: Nov 2000 Location: Huntsville Ontario Canada Posts: 4,052	Re: 89 GMC Cummins conversion Any updates i am curious how everything is holding up ? How about the mpg any better ? __________________ 1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD



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01-18-2015, 02:04 PM	#19
COS399 Registered User Join Date: Dec 2013 Location: Northern, MT Posts: 569	Re: 89 GMC Cummins conversion 72MARIO - Thanks for asking but I haven't had any time to work on it. It will more than likely be a few months before I will get around to it. I just got done watching the first episode of POWERNATION: Truck Tech involving the installation of a LBZ Duramax and Allison combo in a 1987 C10 short bed. __________________ 1987 GMC R2500 SC 454 T400 1988 Chevy R30 CC DRW 12 valve Cummins NV4500 GearVendors

01-26-2015, 02:06 AM	#20
COS399 Registered User Join Date: Dec 2013 Location: Northern, MT Posts: 569	Re: 89 GMC Cummins conversion I know it's not a Chevy and it's not like I have a lot of spare time, but the price was right! That is probably how most of our projects get started. I may one day put it in the "Alternate Tinkering" section. Attached Images __________________ 1987 GMC R2500 SC 454 T400 1988 Chevy R30 CC DRW 12 valve Cummins NV4500 GearVendors

01-26-2015, 11:49 AM	#22
Dieselwrencher 6>8 Plugless........ Join Date: Sep 2007 Location: Prairie City, Ia Posts: 17,140	Re: 89 GMC Cummins conversion That is in really nice shape. What are the plans for it? __________________ Ryan 1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread 1972 GMC Sierra Grande Longhorn 4x4 1972 Chevy Cheyenne Super K20 Long Step side tilt, tach, tow hooks, AC, 350 4 speed 1972 C10 Suburban Custom Deluxe 1969 Chevy milk truck 1971 Camaro RS 5.3 BTR STG3 Cam Super T10 1940 Ford 354 Hemi 46RH Ford 9" on air ride huge project *Tired of spark plugs? Check this out.*

01-26-2015, 01:41 PM	#23
84chevyguyid Registered User Join Date: Feb 2012 Location: Mud Lake, Idaho Posts: 346	Re: 89 GMC Cummins conversion I dont recognize the brand, what is it?

01-26-2015, 09:43 PM	#25
84chevyguyid Registered User Join Date: Feb 2012 Location: Mud Lake, Idaho Posts: 346	Re: 89 GMC Cummins conversion That would have been my guess, what year? Does it still run?

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