Installing D7G Engine and Transmission into D7E48a.

Hello everyone, this is Siro from Argentina, and in my first post, I want to address something crazy and complex with much humility and respect. A while ago, we purchased a D7G, with a destroyed right final drive and undercarriage. The engine, torque converter, and transmission were completely rebuilt, using quality parts and skilled labor. However, due to the high repair costs for the undercarriage and final drive, we decided to buy another D7E48A, which appeared to be in good condition but had some missing parts. As a result, we had to buy a third D7E48A with a destroyed engine to salvage the necessary parts to complete the assembly of the other D7E48A (which is currently operational).

This is the context I wanted to provide. Now, here comes the main topic: would it be possible to install the engine, torque converter, and transmission from the D7G (Serial Number 92V3897) into the D7E48A (Serial Number 48A11821), which has a broken engine and missing parts? (The undercarriage and final drives still appear to have a useful life). Since the transmission couplings look identical, and considering the history from the D7E to the D7G, passing through the D7F, I believe Caterpillar didn’t make significant changes to the differential and final drives between these models. Therefore, if I can install the D7G’s gear and transmission, the gear ratio should remain consistent, and there should be no issues with the transmission ratio. On the other hand, I would keep the mechanical-type steering and brake controls from the D7E48A (without hydraulic assistance), or I could try to install them as well.

I would also need to fabricate the front engine supports and check for compatibility in the rear or make the necessary modifications. Aside from that, I don’t foresee any major issues. It would be extremely helpful to receive concrete opinions with solid reasoning, and there’s no need to tell me I’m crazy (I already know that). In Argentina, spare parts are very expensive, so adapting parts is more convenient, but I hope not to make any serious mistakes. I know the D7G has a more reinforced undercarriage and added weight at the front to improve traction, but this machine will be for personal use and will be treated with great care, so I don’t see an issue with making the adaptation as mentioned.

Thank you very much, I hope you can understand and share with me the knowledge and experiences that the great minds in this group have.

Siro

Hi, Siro.

The D7E was a 4-cylinder engine where the D7F and G were 6-cylinder engines. There was a transmission change part way through the D7F run because the old D7E transmission didn't handle the new 6-cylinder engine with its much higher revs very well. I don't know if they kept the same transmission from the later D7Fs into the D7Gs.

The D7E had hydraulic boosted steering clutches but I think the brakes were mechanical. Likewise with the D7F. I don't know about the D7G which MAY have been the first of the D7s with the inter-connected steering with clutches and brakes both actuated by the steering clutch levers.

I only ever operated one D7F and no D7Gs. The D7F was light on the front but we 'fixed' that. When it came time to put some reinforcing plates on the face of the blade for push-loading scrapers, we used 1 inch - 25 mm - steel plate instead of the usual 1/2 inch or 5/8 inch - 13 mm to 17 mm - plate that was the most commonly used. We bevelled the bottom edges of the plates so that the scraper push blocks would slide up more freely when picking up the scrapers to load them. THAT fixed the light front end issue.

Hope this helps.

Just my 0.02.

Thank you very much, I agree with what you say, I will add that the transmission of the last d7F was the same as that of the d6C, my hope is that the area where the crown and the transmission is screwed has been maintained, being able to place the crown and transmission of the d7G and adapt the 3306 engine by welding the front supports and modifying the rear ones. But maybe I'm wrong and the areas where they are screwed underwent modifications and then it would be impossible to adapt, I hope someone can confirm it or I'll have to take it down to see what I find. Cheers

That may not work out final drive wise with the 48A making full load HP @ 1200 rpm and the 92V @ 2000 rpm.

Hi, Siro.

From what Old Magnet has said, it seems that you could finish up with a 'high-speed dozer' if you go ahead wit this swap, maybe as much as 2/3 faster than the original. That'd raise some eyebrows. Might be a bit problematic out on the job though.

If my understanding is correct - I vaguely remember that actually happening a long time ago - the 7E and 7G undercarriage are pretty much the same. If this is right, is it possible to swap the good 7E undercarriage to the 7G and then repair the final drive?

Just my 0.02.

Hello, thanks for the comment. The final drive on the D7E and D7G is the same; I’ve been checking the manuals. There shouldn’t be any changes in speed since I plan to use the original D7G transmission with its corresponding crown gear, thus maintaining the original ratio. On the other hand, what you suggest about repairing the final drive of the D7G and using the D7E’s track rollers is something I also have in mind, but it involves using tools I don’t have and a much harder job. Thanks, guys!

Are the bevel gears also the same between the E and G? There's that ratio to consider as well. If they are (or at least have the same or close ratio), and the finals are the same, then the logic seems sound.

Yes, most of the D7E and G back end parts are interchangeable as long as you are above s/n 47A3396.

Thank you guys, I hope this works, I will let you know with the problems I find when disassembling and trying to assemble the parts.

Sounds good - by all means do keep us up to date with how the adaptation is going. We like pictures!

Hola Senor Siro,

For me, even if it is tool wise problematic, I would rebuild the D7G final drive with the D7E final drive if they are the same as you state. This has to be much easier than trying to retrofit D7G components into A D7E.

With that said, I do believe providing the transmission pinion is compatible with the crown wheel, you will find there will not be any speed issues as I believe the gearing in the drop box at back of each respective transmission will adjust for the different engine revs.

A further complication could be the saddle underneath the engine not allowing the donor six cylinder version. Maybe give us a full description of the D7G final drive damage.

Kind regards, Wombat