Construction and other equipment - One Herky Jerky 745H

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One Herky Jerky 745H

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Construction and other equipment
Forum Description: everything else with orange (or yellow) paint
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=165790
Printed Date: 06 May 2025 at 9:33am
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Topic: One Herky Jerky 745H

Posted By: Yarmouth Lumber
Subject: One Herky Jerky 745H
Date Posted: 12 Nov 2019 at 2:55pm

Hello everyone from the Redneck State of the North, MAINE!

Background: The shop I work for has a AC 745H. I am currently the only mechanic/Technician/Foreman/Porter/ETC ETC. I have a diesel truck, Class 3 to Class 8 Background. But if it has nuts and bolts, and I have a service manual, I can fix it.

Subj: Looking for some directions to look at regarding a possible transmission and or hydraulic pump issue.

Issues:

1) Once it does start, we have to wait 30-45min minimum before we can even think about it moving.

2) When 1st moving, it's very slow, almost crawling. Once it's warmed up more, it will actually go about 5-10mph, and pick up loads.

3) It is very jerky Left/Right.

Known: It does have a Hydraulic leak somewhere/Everywhere. If I top of the fluid, the issues above are slightly better, but not much, and not for long.

Used for: Transferring sand into plow truck & having a snow pusher for the winter.

TY in advance.

Replies:

Posted By: Eric B
Date Posted: 15 Nov 2019 at 12:14am

Welcome to the forum! Of course there is a lot of guesswork involved so any suggestions are speculations... It sounds a lot like supply of oil to the pump is a problem. Some of these machines would develop a crack in the pick-up tube and suck air and possibly some oil to make for a jerky operation. Any other form of restriction of oil supply such as a plugged screen etc is also a possibility. What kind of oil is in the transmission and what kind and type of oil do you add? Any oil that foams easy will give a jerky operation due to the air bubbles in the oil. I used 30W engine oil in my 745 transmission.

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Currently- WD,WC,3WF's,2 D14's B. Previously- I 600,TL745,200,FL9,FR12,H3,816 LBH. Earth has no sorrow that Heaven cannot heal!

Posted By: DMiller
Date Posted: 15 Nov 2019 at 5:05am

If the trans is similar to my 7G on function most likely the clutch pack seals are toast.

Posted By: Jim.ME
Date Posted: 15 Nov 2019 at 6:40am

From your wording ("But if it has nuts and bolts, and I have a service manual, I can fix it."); I am guessing you don't have a service manual for it, or you wouldn't be asking here with no diagnostic info. You need to find one and do the diagnostic checks for the transmission and hydraulics. You may have a suction leak(s) somewhere. You may have bad seals some where. There could be a sticking valve(s). Many possibilities exist. Short of tearing everything apart and renew it; that is just a crap shot without doing the diagnostics. I worked on some of the AC loaders but it was 35+ years ago and I had the manuals for doing the checks and access to an AC construction dealer, with a good knowledgeable staff to review the results with, at the time. Sorry if this sounds critical, but following the proper diagnostic testing steps is important in my opinion.

Posted By: Yarmouth Lumber
Date Posted: 15 Nov 2019 at 10:24am

ya, that was pretty condescending. I feel I addressed your point with my "Service Manual" comment. I am just trying to get some ideas, not diagnose via keyboard. That is due to me not being familiar with the equipment. Then I can relay that info to the owner to try and influence him to get a technician who is familiar with the equipment over to our yard.

Thanks to everyone else so far who has been helpful.

Posted By: JohnCO
Date Posted: 15 Nov 2019 at 10:50am

Jim must have gotten up before his breakfast this morning and is still grumpy. Most of us on the forum are that way some of the time.

I would have to guess the problem is oil related. I have a 545 which would work fine when it was cool but as it warmed up would get more and more sluggish. Found it would work better if the transmission was overfilled a bit. I run ATF in it. Finally discovered a crack in the suction pipe. To repair, the entire engine, cab and transmission has to be removed. A project I haven't had the time or incentive to attempt. Good luck !

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"If at first you don't succeed, get a bigger hammer"
Allis Express participant

Posted By: Jim.ME
Date Posted: 15 Nov 2019 at 11:31am

Sorry, I didn't mean to be that rough on you. I believe in having manuals and that is the first thing I track down for a machine. Here is a link to a site that has a 745 B parts manual, if you don't have anything for manuals that might help some as I think they were similar. They might be able to help you with manuals, as they have a request form on their manuals link. There are a number of 745 series manuals on eBay right now. The service manuals were in sections and there are some transmission manuals there as well.

https://machine.market/specification-8550" rel="nofollow - 745B manual

I believe those had a sump screen in the transmission, have you checked and cleaned it? Have you changed the transmission and hydraulic filters?

It seems I remember some of the 645 models had a spool in the transmission control valve that would hang at times, delaying movement. I think the 745s used similar transmissions. I remember AC and Fiat Allis used Allison transmissions in many units. I believe the 745 transmission was an Allison TT4720-1. NEW ENGLAND DETROIT DIESEL-ALLISON on Warren avenue might be able to help you with a transmission manual.

The transmission and hydraulic systems should be separate as far as oils and pumps, as I remember. As mentioned a leak on the suction side of either the hydraulic or transmission pump could cause slow or jerky action. Steering being jerky could be in a valve or linkage. Steering and loader hydraulics may be separate pumps using the same reservoir.

Posted By: DougG
Date Posted: 19 Nov 2019 at 6:16pm

I do that too - post on this site just to get past info on things that could be wrong,, - then get the - buy a manual - comments ,, sometimes its a lot faster looking for past experience,, oh well good luck with the loader