Hi -
I have a 1984 GMC Kodiak log truck and i'm trying to find out a) what motors and transmissions it could have come with and b) what motors and transmissions could go into it with little or no fabrication. The VIN is 1GBM7D1Y2EV115836. I am quite sure it had a diesel engine in it originally, possibly a Cat 3208 or Detroit 8.2 liter and possibly a Clark CL-551-5 5-spd manual transmission. There are remnants of diesel-related controls under the dash, and the hood says Diesel 70 on it. A local GM truck dealership contacted GM for me with the VIN and was told that it came with a 454 gas engine, but I'm not convinced of that. It currently has a Chevy 427 gasser in it and an Eaton Road Ranger transmission with 3 ranges and 12 forward speeds. The engine is fair, tranny poor. The truck is very solid and I'd like to put in the proper diesel engine and an appropriate transmission, probably standard. I can get my hands on a 1984 GMC 7000 with a Detroit 8.2 turbo diesel and a 5-spd tranny. I don't yet know the make and model of this tranny. Would these be a possibility? Any info you could provide me with would be greatly appreciated. GVW of the truck is 48,500 - 10,500 front, 38,000 rear. Thanks, John D.

Those usually came with a Detroit 8.2L, with or without a turbo. Some had the Cat 3208, but only if it had the raised cab and taller hood. Otherwise, a 3208 will not fit. That VIN says it has a Cat 3208 (the 8th. character is a 'Y'). The raised cab versions had 4 square headlights under the grille. A few of those trucks had Deere 5.9L's and Deutz air-cooled diesels, but those would be very rare trucks.

C/K Man - thanks for the reply, very helpful. Now I know my truck is the raised cab version and it's looking pretty definitive that it came with a Cat 3208, and probably the Clark 5-spd.

I still need to figure out some things. I'll be getting a donor truck for the engine/tranny swap to makes things easier, so which engine to use? Since I have the higher hood, could I use either the Cat 3208 or the Detroit 8.2? I'm thinking that either of the two would fit the truck pretty well, although with the raised cab there could be a lot of differences at the firewall.

If the 3208 turns out to be the way to go, what years and models of donor trucks would be identical to my truck's engine compartment? So far it seems as if Kodiak and GMC 7000 of this vintage were very closely related. Then, were some of the Cats turbocharged? I've seen quite a few Detroit 8.2's and they've all been turbos, but I've seen mostly non-turbo Cats. I really want a turbo. I've heard, "a diesel engine without a turbo is incomplete." Not universally true, but in a truck, or in my woodchipper, I find it highly desirable. On the other hand, my 50-hp Kubota does fine without one, and I don't have to wait for the turbo to cool down :)

I need all the torque I can get with a 48,500 lb. truck, and being a log truck it's going to weigh that much half of the time. (And they built all the sawmills around here at the top of a hill.) I 'd love to find out how or if the 3208 got tweaked through the years and find one with the most torque I can get that will still fit. Also were the 3208's of that era all equally tuneable (injector pump, injectors, computer) with all internal components identical, so I can just tweak whatever engine I get? (Pardon my ignorance if they don't even have computers).

I just thought of one last (or so i hope) wrinkle. When new, my truck was refitted into a log truck, the main change being the replacement of the single rear axle (22,000 lbs.) with 2 bogie axles (38,500 lbs. combined). I'm thinking that the single axle might have been a 2-spd, hence the 5-spd manual. My axles are not and never will be 2-spd, so I'm thinking the 5-spd manual would be a poor choice, and was quite possibly replaced with something else at the time of the refitting. (Just realized I have to find out who converted the truck and pick their brains.) I'm guessing it was the Eaton 12-forward-speed 3-range manual that's in it now, although it doesn't seem to fit very well. The rear crossmember is about 8 inches forward of the mount holes on the tranny, which is now being held in place with a stout chain. This might be the result of slamming in the Chevy 427, I'll have to study the tranny mounts more closely. Lastly, did these trucks come with automatics (Allison I would hope) so I could have that option?

Again, thanks for responding to my post, and if you can help me with even 1 of the 50 questions I just asked I'd sure appreciate it, as I appeciate your putting me on the right track :) John D.

O.K., here we go- those trucks had either the Detroit 8.2L or the Cat 3208. Either one should fit fine. Every 1980-1989 Topkick and Kodiak with the 3208 that I ever saw was turbo'ed, though many Fords had natural 3208's. Comparing the 3208 to the 8.2L:, I think the 3208 was a better engine. The 8.2L was good at blowing head gaskets, particularly if it was a 200 h.p. or better turbo model. The 8.2L has been out of production for just about 15 years now, and parts are starting to get a little scarce. 3208 parts are no problem at all. Neither the 3208 or the 8.2L had computers, and about the most powerful 3208 offered in a medium was 250 h.p. and 650 ft. lbs., as I remember. I think the most an 8.2L was good for was 230 h.p. and maybe 575 ft. lbs., but durability would probably be an issue at that output. As for transmissions, you are probably right, that truck very well could have been a 5 speed with a 2 speed. axle. That Eaton you have in their might work with a diesel, you should get the number off of it and figure out exactly what model it is to find out what the ratios are. I don't quite understand what the chain is doing, usually these transmissions just hang off of the clutch housing. Allisons were offered with the 427, 8.2L, and 3208 in these trucks. I think your best bet would be to find a 3208 doner truck and transfer everything over. Be advised, the 3208 is a tight fit in these trucks. You have to unbolt the front cab mounts, loosen the rear ones, and lift up the front of the cab to get the engine in. Look for a 1980-1989 3208 Kodiak or Topkick donor. They made a lot of those, so it shouldn't be too much trouble. Also, a lot of Brigadiers had 3208's, but you might not be able to use the mounts and such. Good luck!

C/K Man - Thanks once again for that excellent response, great information. The only other person on the entire internet that I've gotten a lot of info from (backing you up all the way) is a guy who goes by the name Kaptain Kodiak (Charley Anton). His website is smartspeckodiaks.com., and he has quite a background in these trucks from late 70's on. Check it out, it's pretty interesting.

It was good to know that I should absolutely rule out the Detroit 8.2 - I've had unanimous agreement with your observation that they have some problems - can't take the boost, blow head gaskets, and leak a lot. Add in the fact that the more reliable 250hp Cat will put out a lot more torque, and case closed. I was on schoolbusfleet.com in the "bus garage" forum and got an earful about the problems with the turbo Detroits - very informative site.

The tranny i would get without a doubt is the 8N. Charley/KK says the Kodiak/Topkick never had that transmission as an option (from 80-89 anyway) but that it should fit in just fine. He also told me that the 3rd digit of the tranny model number tells you the torque capacity in 100's, so I'd want 7 or 8 i guess. I have to check out all my ratios as you suggest, but I'm pretty sure the rear is geared for the diesel engine, making this thing undrivable for all practical purposes. Major disappointment, I need a log truck immediately, so unless a good donor appears in the next week I'm going to have bail on this one for now and grab a good used 80's vintage Kodiak log truck set up the way I want it - they can be had for around $15,000. I haven't committed to buying this truck yet, I wanted to find out which end is up with it first. I'm pretty sure I'll bring it back to life eventually, it's a very solid truck.

If I had the time and energy I'd attach Charley's replies, about four of them so far, chock full of good info just like yours. Let me know if you want me to post them. And oh yeah, the attachment is a picture of the beast we've been talking about.

Thanks again for all the excellent help, John D.

So, you found 'Kaptian Kodiak'? He is supposed to be one of the best G.M. commercial truck salesmen in the country. Can't go wrong listening to him. Anyway, glad to help you out. I am a shop foreman for a major utility here is Southern California, and we had a lot of those trucks over the years. I drove a '89 TopKick with a 3208 and an Allison MT 653 almost every day, and it was one of the best medium duties we ever had. About all I ever did to it was change the oil. Good luck!