'89 GMC 1500 Cummins complete!

[KMahnke]

Well It's driving now--'89 half ton reg cab long bed, 1990 6bt cummins with----TH400 GM transmission with custom built low stall 13" six bolt converter, 2:76 12 bolt rear with G 80 locker. Pinnacle 3 1/2"--4" mandrel bent exhaust with custom fabbed downpipe. Hybrid motor mounts and custom hacked/fabbed fan shroud. Light truck--strong engine & tight converter with tall gears=nice road machine. Hard to get engine up to 140 op temp. Got a custom transmission pan for the 400. Deep aluminum casting includes solid t/c cover that bolts to bellhousing adapter and is one part with oil pan. Finned with drain plug! Came from 4bt cracker van with th400. using stock GM single row v8 alum radiator. power steering lines bolted right up. one bad vacuum pod--needs to be replaced. Major pains were starter clearance on passenger side A arm attachment and pass side motor mount stud and bolt thru frame. If I had it to do again I would rethink this mount. Highest EGT's in the 850 range and about 27 lbs boost before defuel. Truck is strong and smooth. Need to fix the drivers side window operator and motor re calibrate the speedo and re clearance some exhaust parts (muffler hittihg drive shaft) and she'll be ready for my daughter to drive to school after new years :-laf



Three Cummins in the family now--one wrapped in a GMC!



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[Glen Pratt]

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Nice work. Like a glove. Looks like it was meant to be there. -Glen

 

[AndrewKing]

I like that!... . How does it drive handling wise?... . I've heard many say that 1/2 tons are hard to use because of the Cummins weight issue..... Maybe you proved them wrong... .

I like the idea of a light truck with the Cummins... . Should be a great performer and get good MPGs too..... Let us know how it does... Great Job!

Andrew

 

[KMahnke]

Thanks Guys. Used the trw load handler front springs for big block/diesel application with air etc. all new ball joints and tie rod ends to tighten her up a bit. Brakes are ok especially with the 11. 5" drums on the ol 12 bolt out back. 2" body lift kit didn't add any perceptable roll or other handling difficulties. Truck handles like new! Dont even know that ol 1,000 lb block of iron is up there--until you roll into the pedal a tad . transmission seems to be handling it well so far--cooler and lines have been reasonably warm to the touch--not hot at all. Trans was built for a 7krpm 400+ hp 383 stroker and lived behind it on the street for a year or so with a 10" converter. Shifts firmly but reasonable. will report on fuel mileage when speedo gets recal'd.

 

[KYLE4]

That is awesome nice work

 

[robbiesworld]

Thats pretty cool!!!! Looks like alot of work NICE JOB

 

[DPinkston]

Looks good. They were putting 454's in those models and it ain't no lightweight, though I'm sure the Cummins still has 200lbs on it.

Danny

 

[JLEONARD]

Looks very comfortable in there... nice job.

Jay

 

[BV]

Looking good - Did you have to do any work on the firewall?

 

[HoleshotHolset]

Major pains were starter clearance on passenger side...

Wait - doesn't the starter normally mount on the driver's side?



This looks like a VERY doable conversion - I've always been a Chevy guy... . hrmm...



EXCELLENT work. I'm jealous of your daughter... that's going to be the coolest rig at school.



Matt

 

[DPinkston]

Wait - doesn't the starter normally mount on the driver's side?

Matt

In Dodge applications yes. My Ford mounts on the right as well. The adapter plate positions the starter on whatever side the bellhousing has the starter bulge on. I had to grind a small amount off the inside of the bellhousing for the starter nose to clear. I think BV did too. I have a ZF and I believe he has an E4OD.

Danny

 

[KMahnke]

BV--no firewall mods necessary. about 1 1/2" clearance between the cylinder head and firewall. Did add a 2" body lift though. The Cummins is not only long but that stroke and deep skirted block takes up a lot of space too!



HolsetHoleshot--Starter mounts in the Chevy location with the GM adapter. Used a starter for Case 4B/6B applications I found on E Bay for about $160. Solenoid sticks out like a sore thumb. Had to heat and notch the rear upper A arm mount for clearance. Also pulled the drivers side motor mount over an inch farther than the passengers side. I think the GM frame is offset as the Cummins sat crooked when we test bedded it. The adapter puts a 4 degree or so tilt on the motor or trans --take your pick--I favored the passenger side tilt a degree or so and the trans is slightly cocked a bit to the drivers side. Cross member and original trans mount went into factory holes but I did notch for pan clearance.



Yes she is lucky and cant wait to drive it--if I can let it go :-laf

 

[HoleshotHolset]

Did add a 2" body lift though.

Could it have been done without the body lift? I've never been a fan of body lifts...

Starter mounts in the Chevy location with the GM adapter.

Okay - that makes perfect sense now. Chevy should have taken the Dodge route and crammed all of the stuff on the driver's side. That makes putting two turbos on the passenger side a walk in the park.

Yes she is lucky and cant wait to drive it--if I can let it go :-laf

I look forward to hearing more about this. Mom used to drive a '96 2-door Tahoe 4x4 with the 6. 5L TD/4L80-E combo. When I showed Dad this thread - he wishes he wouldn't have gotten rid of that Tahoe.



Sounds like we have another dieselhead in the making... gotta love it.



Matt

 

[KMahnke]

It would have worked without the body lift but things were getting pretty tight in the firewall/bellhousing adapter area. Also had to rake the motor back at a pretty good angle --below the natural position of the rear trans mount. Kit was relatively cheap and took an afternoon to install--modified the rear bumper brackets though to get full use out of the reese hitch on the truck--still not happy with the way the front bumper came out. Slight rake and tweaked a touch.



Ordered the speedo calibration kit and harness from GM today as well as a new drivers side window regulator. when this stuff gets bolted in the keys will be ready to hand over to her.



Oh yeay I found a pretty good deal on vacuum pods for first gen engines @ rock Auto. Cheaper than anything I could find around here locally. Cardone vacuum pump #641300. The first gen guys might want to check this out.



Pretty cool around here in the morning with three Cummins engines warming up in the driveway. Music to my ears--brings a tear to my eye--oh wait thats the smoke!

 

[HoleshotHolset]

It would have worked without the body lift but things were getting pretty tight in the firewall/bellhousing adapter area.

I hate to be a pain about this... but, how tight was it? I despise body lifts and would rather massage the firewall a bit rather than lift the body. From your description - it doesn't sound that bad at all.



By the way - TDR members get a 5% discount on all orders from RockAuto.com I have a thread that describes all about it - check the thread out here.



Pretty soon I'll have two 12-valve, P-pumped Cummins/Dodges in my garage - it brings tears to my eyes to know that I'll have both of the 'kids' living in the same house. :-laf



Matt

 

[KMahnke]

Holeshot--some hammer massaging would have worked or I could have simply brought the motor forward a little more to let the bolts clear the trans tunnel. My main concern was getting enough clearance between the radiator and the fan.



Thanks for the tip on the rockauto discount!

 

[HoleshotHolset]

10-4 on the 'hammer massaging' - anything to avoid a body lift.

I find it really cool that you were able to use an engine driven fan - I would have never guessed that it would all fit in there.



No problem - the RockAuto.com deal has worked out great for a lot of folks so far.



Thanks for answering my queries,



Matt

 

[RyanB]

10-4 on the 'hammer massaging' - anything to avoid a body lift.

I find it really cool that you were able to use an engine driven fan - I would have never guessed that it would all fit in there.



No problem - the RockAuto.com deal has worked out great for a lot of folks so far.



Thanks for answering my queries,



Matt

I am very glad to see these pictures and as soon as I get my digital camera I will be sure to post pic's of my GMC conversion also. I am totally against the body lift and I chose to massage the firewall. Turns out I didn't even need to do anything to the firewall. I put in a 12valve and a 6-speed. I made a custom cross-member for the 6-speed and the stock crossmember below the engine I cut 1" off it and there fore was able to drop the engine and transmission down to the point so the head was 1. 25" from the firewall. I then put in the rad and the fan blades were 1/4" from the rad :--) I thought this wasn't nearly far enough away but the center hub was okay being 1/4" away seeing it doesn't move. What I did was take the fan & hub to my local machine shop and he made me a 5/8" spacer to pull the fan back to being 7/8" away from the rad which is what the stock Dodges are. The rad is sitting in the stock location but I ran into major problems with the Intercooler. I wasn't able to put in a dodge intercooler so I went a brand new D-Max cooler that fit great other than that I had to chop and mod the rad support. In the end it worked great but I did have to put a 1/4" spacer between the rad support and the lights which make them stick 1/8" out past the grill but if you didn't know it you would think its stock. I am also building a custom front bummer for the truck and relocating the batteries down to the bumper which will make a ton of room. My truck is also a 2 wheel drive..... we the frame is anyway!!!!!!! Oo. Oo. Oo. I really wanted to run A/C but couldn't run it in the stock location due to frame clearance so I thought about and tried to mount it ontop of the motor like some of the ford conversions do but in the end there was only 1/4" from the hood lining so I thought about something else. I cut and notched the frame and now it looks totally stock and everything fits in great!!!!



If anyone has any questions feel free to ask and in the future I will post some pics..... Ryan

 

[camsv3500]

pics please... .

and a followup on both these trucks for driveability and fuel mileage... and mr murphy problems would be really nice... .

excellent work

If you both dont mind Im going to copy some of your info for my permanent chevy cummins tech thread over at ck5

thanks

cam

 

[KMahnke]

As far as driveability goes this seems to be the perfect truck. From my biased views toward the '88-99 GM body style to the superiority of the Cummins this in my opinion is a package the MFG's should have put together a long time ago. They cant see the forest from the trees when it come to what would really dominate a market segment. This thing is smooth---better ride than my '01 duramax crew cab, quieter than my '95 12 valve and a heck of a lot better riding. It is only a half ton and i expect nothing more than a half ton truck is capable of. It will however be able to do what I require of it for a heck of a lot longer than any factory package GM ever put out in that era of bodystyle. Parts are cheap and readily available for the entire pakage.



You are welcome to use info to help anyone in a public or private forum. All I ask is that credit is given where credit is due for the pics. If you need more detail just let me know. I can E Mail or post more as requested. Any help or information I may have to further someones creative talents will be shared freely.



Mileage is gonna be kind of tough to figure accurately as the odometer gave up at around 120,000. I will give you a good rough estimate after a couple of tankfulls have been run through it.



There are details such as adapting the old 12 bolt to the new body and availability of low numerical gearsets (2:73 and such) and compatable lockers etc. Also I have the part numbers for the required harness, tire size/pin chart and pins to calibrate the speedo--specific to 1988-92 trucks before obd2 diagnostics.



I am badgering a couple of transmission rebuildrs in the 700-R4 market to come up with something they will stand behind to beta test for the Cummins. If I could come up with something with od and lockup (combined with a little more pump tweaking and a GSK) this thing would be absolutely dangerous at highway speeds. With the 3:73's My son's 01 24 valve with 275 injectors and comp could not keep up with it until he hit third with converter lockup (of course in all fairness his converter is pushed to the max as far as stall speed is concerned--DTT goodies are sitting on the shelf in the garage, but thats another story). Then it was Bye Bye GMC. It would accellerate to defueling like a rocket (about 65 mph). Don't need no stinkin' 14CM housing--nothing even remotely close to turbo lag--just instant on with nothing but screwdriver mods to the VE.



Handed her the Keys over the weekend. Grinning from ear to ear. The'ol boys at school were beginning to think this thing was all story! I expect a lot of questions in an era of TBI and "flowmaster" bellybutton trucks.