I can't believe there's no "GMC Engine Options?" thread LOL

tmsnyder

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Oct 7, 2019
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This has been beat to death obviously, elsewhere, and my 455 seems healthy for now. But who doesn't love a good project?

Have any of you gearheads thought about the front wheel drive, diesel, Ram Promaster drivetrain as a possible swap option? I just saw one sell quick on ebay, low miles, t-boned damage on the side but front looked fine, for less then $7k.

I wonder how hard it would be to make that engine / tranny work?
 

6cuda6

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Oct 3, 2019
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As they say....anything is do able with enough time, skills and money.

Most of the time the limiting factor is your trying to move 12000lbs instead of about 6000lbs so car/suv stuff just is not built strong enough these days.....it would work but not for very long. (Plus im not sure if id want an 8 speed or 10 speed as the thing would be shifting all the time.)
 
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tmsnyder

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Promaster is a delivery van, there are 1500, 2500 and 3500 versions of it. A 6000lb half ton truck carrying / towing 5000 lb is reasonable to expect imo. It should be able to cut it but who knows how it would hold up over time? Depends on the design and the quality and I'm not sure the longevity of those vans in general. Maybe they're junk from the start, or maybe they're well made and would last a long time. I haven't looked into it.

Depending on how someone drives they might find it a little lacking in the hp category though. The extra gears, especially a low 1st gear might really help though, and that OD would be nice. But the little I4 diesel wouldn't be great in the hills or towing a toad.
 

johnny

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Oct 28, 2019
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My dealer tells me they've dropped the diesel promaster in this country. Maybe it will be back with the MV v6 diesel later.
 
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Mike Perez

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Oct 2, 2019
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This has been beat to death obviously, elsewhere, and my 455 seems healthy for now. But who doesn't love a good project?

Have any of you gearheads thought about the front wheel drive, diesel, Ram Promaster drivetrain as a possible swap option? I just saw one sell quick on ebay, low miles, t-boned damage on the side but front looked fine, for less then $7k.

I wonder how hard it would be to make that engine / tranny work?
The transmission SUCKS. It is an old 4 spd minivan transmission that had the fourth gear taken out and a "doubler" added to get 6 gears. It is horrendous. If they ever come out with a good transmission designed for the Promaster, then it may be a viable swap.
 
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johnny

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I've had good luck with it in my minivans but it (the trans) is too light for a GMC I think. Now, if you could get the MV and 9 speed out of the pickup sideways.....

--johnny
 

1976GMC

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Oct 14, 2019
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I've been looking at the modern FWD options to swap into GMC. I too have looked at the Promaster. Having zero experience driving one of them I've just focused on checking their specs. Yes, our GMC is 12,000+ lbs vs Promaster 6,000 lbs, so the question if that engine/transmission setup will be up to moving extra weight down the road is reasonable. Promaster is designed to tow a trailer too. The GCVW for 1-ton Promaster (loaded van plus trailer) is 11,500 lbs. That is getting pretty darn close to what we need to move. Don't forget, the original power plant that is currently in our vehicles was designed to move only 4,500 lb. Toronado. It was later put into GMC MH. This means we are 3x over the original "capability/capacity". It would be nice to know how much safety margin is built into the modern engine/transmission as far as load capacity.

Another option that i've mentaly entertaining is the Unimog power plant with the front wheel drive only. I've seen videos of couple Unimogs that are built that way, but i do not know how far back transmission extends. Those units themselves are 6,000-8,000 kg (13,000-17,000 lbs) plus they can tow another 6,000+ kg (13,000 lb) trailer. I doubt there will be any issues with exceeding designed capacity on the engine or transmission there. The question is - can we squeeze that under our hood?...
 

johnny

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Oct 28, 2019
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There are plenty of engines out there, both Oldsmobile and Cadillac , but so far no transmissions other than the THM-425 which can be used without major surgery. Hard parts for it are becoming unobtanium since many of them are common only to it. You mechanical gurus need to be addressing this problem.
DOS Tip: If you find a dealer or a shop with an NOS THM-425 drive chain on the shelf, BUY IT!!!

--johnny
 

tmsnyder

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Oct 7, 2019
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Aaaack, the old Chrysler minivan transmission? Run! LOL Just kidding to a certain extent, I read they beefed it up a bit . Maybe with the Pentastar gas engine instead of the diesel, and a monster fluid chiller it would hold up better. At least parts would be available. Who knows, maybe some smart tranny guy could bulletproof it!
 

Mike Perez

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Oct 2, 2019
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I've been looking at the modern FWD options to swap into GMC. I too have looked at the Promaster. Having zero experience driving one of them I've just focused on checking their specs. Yes, our GMC is 12,000+ lbs vs Promaster 6,000 lbs, so the question if that engine/transmission setup will be up to moving extra weight down the road is reasonable. Promaster is designed to tow a trailer too. The GCVW for 1-ton Promaster (loaded van plus trailer) is 11,500 lbs. That is getting pretty darn close to what we need to move. Don't forget, the original power plant that is currently in our vehicles was designed to move only 4,500 lb. Toronado. It was later put into GMC MH. This means we are 3x over the original "capability/capacity". It would be nice to know how much safety margin is built into the modern engine/transmission as far as load capacity.

Another option that i've mentaly entertaining is the Unimog power plant with the front wheel drive only. I've seen videos of couple Unimogs that are built that way, but i do not know how far back transmission extends. Those units themselves are 6,000-8,000 kg (13,000-17,000 lbs) plus they can tow another 6,000+ kg (13,000 lb) trailer. I doubt there will be any issues with exceeding designed capacity on the engine or transmission there. The question is - can we squeeze that under our hood?...
[/QUOT
I've been looking at the modern FWD options to swap into GMC. I too have looked at the Promaster. Having zero experience driving one of them I've just focused on checking their specs. Yes, our GMC is 12,000+ lbs vs Promaster 6,000 lbs, so the question if that engine/transmission setup will be up to moving extra weight down the road is reasonable. Promaster is designed to tow a trailer too. The GCVW for 1-ton Promaster (loaded van plus trailer) is 11,500 lbs. That is getting pretty darn close to what we need to move. Don't forget, the original power plant that is currently in our vehicles was designed to move only 4,500 lb. Toronado. It was later put into GMC MH. This means we are 3x over the original "capability/capacity". It would be nice to know how much safety margin is built into the modern engine/transmission as far as load capacity.

Another option that i've mentaly entertaining is the Unimog power plant with the front wheel drive only. I've seen videos of couple Unimogs that are built that way, but i do not know how far back transmission extends. Those units themselves are 6,000-8,000 kg (13,000-17,000 lbs) plus they can tow another 6,000+ kg (13,000 lb) trailer. I doubt there will be any issues with exceeding designed capacity on the engine or transmission there. The question is - can we squeeze that under our hood?...
I thought the GVWR on the Promaster 3500 was just under 10,000. Either way, what's the point? Major surgery to get minor gains. Electric motors with a gas driven engine/generator is a better option I think......eventually.
 
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1976GMC

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Oct 14, 2019
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That is not a terrible idea. You kind of having the best of both worlds here - easily available and transportable concentrated power (gasoline) and direct drive electric motors on wheels. Depending on how technology develops, perhaps one can add them onto the middle axle too. Having traveled in the winter in the Pacific Northwest I found myself on several occasions wishing GMC had another pair of drive wheels. I bet you wouldn't need the 455 behemoth under the hood to drive the generator ether.
 

Mike Perez

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That is not a terrible idea. You kind of having the best of both worlds here - easily available and transportable concentrated power (gasoline) and direct drive electric motors on wheels. Depending on how technology develops, perhaps one can add them onto the middle axle too. Having traveled in the winter in the Pacific Northwest I found myself on several occasions wishing GMC had another pair of drive wheels. I bet you wouldn't need the 455 behemoth under the hood to drive the generator ether.
Small turbo-charged 4 cylinder would enough. The thing with gasoline engines is that they have to be sized to where they make enough power for all situations. That's why there is a big V8 in there. So let's just say that a GMC typically takes 100 HP to move down the road at 60 mph on level ground. However, it takes more than that to accelerate or go up hill and it takes way less to idle downhill or stopped. 100 HP converts to 74,570 watts. If you add a large battery as a buffer to take up the slack for when you are going up hill or accelerating, then all you would need would be a generator that could put out enough electricity to average what you are using.

If you look at the numbers above, you'll see why I"m skeptical on having a pure EV conversion any time soon. Cruising down the freeway, at 60 mph, you'd use 74,570 watts (as an example) of electricity in an hour. That's basically one Tesla Model S battery an hour. So even if you triple the battery, you'd have to recharge in 3 hours. Now you'd be charging a massive battery. Current superchargers charge to 80% in 40 minutes, so It would take two hours at that rate. So if you don't mind charging two hours for every 3 of driving, it could work.

I just found an 83kW alternator online as an example, it requires 166 HP for gasoline and 128 for diesel. It also weighs 755 lbs. So that's before the engine and the electric motors and the batteries. I don't know, maybe all electric would be ultimately better if you can find a way to get 8 hours of driving in between charging. It's not for me though.
 

johnny

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Oct 28, 2019
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166 gas and 128 diesel? It is an alternator with ESP and thus can tell what fuel the prime mover uses? Can you explain this a bit further?
 

Mike Perez

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166 gas and 128 diesel? It is an alternator with ESP and thus can tell what fuel the prime mover uses? Can you explain this a bit further?
It was just what was quoted. Maybe due to the higher torque of the diesel.
 

tmsnyder

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Oct 7, 2019
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What's the difference between an Olds Toronado engine and tranny and the GMC? There seems to be no shortage of running Toro's for sale out there.
 

1976GMC

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Washington State
I think they are just about the same. Manny's transmissions have Power Drive belt setup (more torque) and possibly more clutch plates? Please correct me if I'm wrong on that.
 

Daniel

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Oct 9, 2019
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Landgraaf, the Netherlands
BTW .... the newest Fiat Ducato TurboDiesel, gets stronger crankshaft and bearings, starting with the 160 HP and 180 HP engines, almost 400 Nm of Torx and > 400 Nm for the 180 HP two stage TurboDiesels, and available with the all new ZF, 9-Speed Automatic transmission, much better then the till now used 6 speed robotic auto transmission.

as I hear, ProMaster, which base in fact by FCA was based on the Fiat Ducato, only does offer 6 cylinder gas engines ...
in my opinion the old 150 and 180 HP TurboDiesels with 6-Speed Stickshift already would not have a problem with the weight of the GMC, the newer ones even less ...

ok ..l much towing would be a problem perhaps, but ... all is possible.

bye Daniel
 

tmsnyder

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Oct 7, 2019
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Imagine what all that work would cost if someone had to pay for it. wow, not exactly an easy swap!

It will be interesting to see its performance, I suspect a lot of people in the US would say that it's way too underpowered for this side of the pond. With no Toad however, and staying out of the mountains, I would suspect that it would work for me personally.




Hi TM ......

actualy, a fellow Dutchman is doing this right now ...
Facebook page of the GMCato 3.0 ... merging a GMC 23 with a Fiat Ducato 3 liter TurboDiesel
he even made first successful driving tests:
Drive tests GMC+Ducato front wheel drive TurboDiesel

bye Daniel
 

JSanford

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Oct 4, 2019
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What's the difference between an Olds Toronado engine and tranny and the GMC? There seems to be no shortage of running Toro's for sale out there.
No difference, the THM425 was used in 1966-78 Olds Toronado and 1967-78 Cadillac Eldorado.

If you are looking for a more powerful engine than the low compression 455 that the GMCs came with your easiest route is to go with one of the pre-1971 high compression engines that was mated to the THM425 in the Toronado or Eldorado:
Olds 425
Olds 455
Cadillac 429
Cadillac 472
Cadillac 500
 
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