3 speed auto rebuild or convert to 4 speed auto?

[Dieselnut59]

I have a friend with a 1989 250 4x4 with the 3 speed auto and (I believe) 3. 08 gears. He is looking to either upgrade to a 4-speed auto transmission (if not to difficult) or beef up/rebuild the 3-speed. Ideally, he wants to upgrade to the 4-speed and keep the 3. 08 gears so he can run in 3rd when pulling and have 4th for highway fuel economy.

How involved is a swap to a 4 speed auto. and approximately how much would it cost? Thanks for the help!

John

 

[Philip]

If he is planing on swaping to a OD trans. I would look for a trans out of a second gen to get the lockup converter. There are more of them out there than 1st gen A518's. Price is supply and demand. They are out there. But most are not cheap for eather generation of trucks.



I have 3:08's in my truck with a OD trans. I pull in OD all the time. The only time it comes out is when the speed is under 60 MPH. So unless he is pulling overloaded all the time. I wouldn't worry about hauling in OD.

 

[1stgen4evr]

auto rebuild or convert to OD

There is a very good chance that his ratio is 3:07 but not absolutely. Even so, the OD transmission will take the load to a point. My late 92 OD has a 3:54 rear and has 285k miles. I have never worried about the transmission except the hunting in and out of OD. It has lost some torque converter function and will need attention before I put many more miles on it. If he gets the converter to match his job, it will perform very nicely. Really depends what his loads are. Now if you are talking loads like the fellows in Elberton lay on, maybe not. Those rock are heavy.



Your friend can look at your cab/chassie and see all that is required except the drive shaft changes. He will want to install the OD control on the lever as others have described.



Sending along a PM as well.



1stgen4evr

James

 

[bgilbert]

A518 only used in diesel apps? What auto-od did gassers use? If same are the diesel 518's beefed up like the 727 modified behind the diesel is? Cause I got a 89 auto-od 2wd gasser pu in the works for parts, very large tree fell on it ...

 

[rowland]

The swap to a A518 isn't bad. You do have to shorten/lengthen the driveshafts and wire in the overdrive. I didn't even have to move the T-case cross member, although the front driveshaft clearance is pretty close at full droop.



The later model transmission is supposed to be a little better, you do have to wire in the lockup and operate it manually and I think it might need a late model starter. It's been done before so I'm sure somebody here has the scoop.



As for price, the first shop I went to looking for a rebuild happened to have an A518 lying in the corner they had just pulled out of a wrecked '93. Got the transmission and T-case together for $600. Not sure how good of a deal it was, but since it was the only deal going, I was happy. There is a fairly significant amount of labor involved, but really not any more than doing a full rebuild on the original.



The great benefit is that now I can finally pass people! Not to mention cruising at a reasonable rpm is great.



Isaac

 

[dan brooks]

From the info I found, the engine adapter and starter will need to be changed when going from a non-lockup to a lockup converter, plus driveshaft and (maybe) crossmember mods, so that may be something to consider, or at least research a little more.



Other than not being able to effectively use an exhaust brake, I'm very happy with my upgraded A-518: good rebuild with the TransGo TFOD-Diesel shift kit and a Hughes converter.



I have 3. 54 gears and sometimes wish I had 4. 10s when I have the camper on and the Jeep hooked up, so the 3. 07s may not be ideal for the OD trans when heavily loaded. Of course, kicking it out of OD will give the same performance he currently has with the 727. The fuel mileage will probably be awesome for unloaded freeway driving, though.



If he does go with a lockup trans, I'd suggest a high quality upgrade converter. After seeing the size of the stock lockup clutch, I'm surprised they hold up to the Cummins under normal driving, much less the added stress of BOMBs and/or an exhaust brake.

 

[Philip]

A518 only used in diesel apps? What auto-od did gassers use? If same are the diesel 518's beefed up like the 727 modified behind the diesel is? Cause I got a 89 auto-od 2wd gasser pu in the works for parts, very large tree fell on it ...

The 518 was used behind gasser trucks also. But the gas engine model was built weaker and the bolt pattern is different on the bell housing.

 

[Dieselnut59]

He just crashed the truck, so I am not sure what the deal on the transmission will be. Seems like a lot of work for a overworked truck. He does haul HEAVY and frequently... WAY more than I would want to do even with my 3500/manual trans setups.

 

[Paul Herioux]

I love my setup for the last 4 years. If your friend does this urge him to spend the money up front for a good torque converter. I didn't and it is the only sore point in the whole deal. Search my posts, I did a fairly detailed write up on what is involved.



Later,

Paul