1986 F-250 XLT 6.9 idi C6 switch to 300 4 speed

[FuzzFace2]

You are right Jim I need to look at the countershaft low gear.

Hopefully I will be able to inspect it when I pull the PTO cover.

My experience with these transmissions is that low is only used from a standing start with a load or when you want to creep the vehicle. I would guess the damage was done from not letting the countershaft spin down before attempting engagement.

My solution for that is to engage 2nd to stop the countershaft and then attempt to engage low.

I can't imagine anyone downshifting from 2nd to low (more than once) while the truck is moving but who knows. I have seen pictures of these gears in much worse shape and with every tooth ground down. The picture I took is of the worst part of the gear so I think it was just something that happened only occasionally. I will let you know the condition of the countershaft gear but I don't think I will be able to get a picture.

I would also check out reverse gear as it is also a straight tooth gear and could be like that one.

The T18 I pulled from my 81 F100 was in pretty bad shape and being I was using the truck felt it best to swap in a different transmission, went with a NP435.

The NP435 has its little issue when cold but I can live with them till I figure if I want to deal with it or not.

What has helped with shifting is I drained the fresh W75-90 gear oil and filled it with Red Line MT-90.

Dave ----

 

[nic55kel]

I would also check out reverse gear as it is also a straight tooth gear and could be like that one.

The T18 I pulled from my 81 F100 was in pretty bad shape and being I was using the truck felt it best to swap in a different transmission, went with a NP435.

The NP435 has its little issue when cold but I can live with them till I figure if I want to deal with it or not.

What has helped with shifting is I drained the fresh W75-90 gear oil and filled it with Red Line MT-90.

Dave ----

Dave the reverse idler looks pretty good.

You can just see it by the date stamp in the first picture of the open gearbox.

Yes I have driven T98, T18 and NP435 and getting the right fluid in them to match the environment makes a huge difference.

On my NP435, as I recall, I put in a synthetic GL4 75-90 and that worked really well even at -40.

I remember back with that old T98 at -40, needing both hands on the stick to get it into neutral after parking it in low and when you first let the clutch out in neutral it would stall the engine if you weren't careful.

After reviewing a couple of T18 rebuilds and pictures of worn gears I don't think those gear chips are too serious. I am always careful about engaging low and don't use it that much so I am sure the transmission will outlast me just the way it is.

 

[ArdWrknTrk]

Well I really lucked out on the clutch. It appears the clutch is brand new and the flywheel appears to be as well. I had thought that the ring gear was in much worse shape than it really is - just a couple of small chips on two teeth. Has a needle pilot bearing and I am sure the release bearing is also new (20 odd years ago).

Starting to think I will not have to do much to this drivetrain at all.

The rear main seal looks nice and dry on the engine but the oil pan and valve cover gaskets are both pretty wet so I will reseal those and while I am at it I will pull the timing cover and change the seal. I want to be sure that the cam gear is cast iron.

That's great news!

[nic55kel]

That's great news!

Thanks Jim, yes things are going quite well.

I pulled the engine today. It was a tight fit but I had loosened the rad support so I could move it a couple of inches forward at the top and that really helped.

I really don't like ford electrical connectors and when they are 40 years old I REALLY don't like them. I gave up on them and cut the harness.

I love the simplicity of these old engines - two vacuum hoses other than the brake booster - doesn't get much simpler than that.

I see the exhaust bleed line to the choke is broken off but other than that everything looks to be in good shape.

I have a lot of cleaning to do.

 

[Gary Lewis]

Thanks Jim, yes things are going quite well.

I pulled the engine today. It was a tight fit but I had loosened the rad support so I could move it a couple of inches forward at the top and that really helped.

I really don't like ford electrical connectors and when they are 40 years old I REALLY don't like them. I gave up on them and cut the harness.

I love the simplicity of these old engines - two vacuum hoses other than the brake booster - doesn't get much simpler than that.

I see the exhaust bleed line to the choke is broken off but other than that everything looks to be in good shape.

I have a lot of cleaning to do.

Looking good!

[oldmansimek]

Looking good!

I have gotten rid of the barrel plugs on most of my trucks, I use the gm weatherpack connectors. I have to say you should keep the sterling and 4.10 gears, it is a better rear and you will be suffering on power with the higher ratio and a very heavy truck.

[nic55kel]

I have gotten rid of the barrel plugs on most of my trucks, I use the gm weatherpack connectors. I have to say you should keep the sterling and 4.10 gears, it is a better rear and you will be suffering on power with the higher ratio and a very heavy truck.

Hello Oldman - sorry don't see your name.

I really prefer the GM connectors and that is what I was thinking of switching to.

I am keeping the sterling but it has the 3.55 gears in it.

I know it will be underpowered compared to today's vehicles but we are flatlanders here and I am getting older and slower.

The truck isn't going to be a daily driver just for going to the dump, picking things up and Sunday drives.

Speaking of heavy trucks, I scaled my 07 F250 the other day - 7700lbs empty.

It has a tommy gate so that adds but still I was surprised.

[oldmansimek]

Hello Oldman - sorry don't see your name.

I really prefer the GM connectors and that is what I was thinking of switching to.

I am keeping the sterling but it has the 3.55 gears in it.

I know it will be underpowered compared to today's vehicles but we are flatlanders here and I am getting older and slower.

The truck isn't going to be a daily driver just for going to the dump, picking things up and Sunday drives.

Speaking of heavy trucks, I scaled my 07 F250 the other day - 7700lbs empty.

It has a tommy gate so that adds but still I was surprised.

Names Ryan, still trying to set up my signature picture and info. Sorry thought I read it was 4.10's, you should be fine. I am of the belief that the ford 300 might be the best motor they ever made. Years ago I had an 85 f150 reg. cab flareside 2wd that I drove for years it had over 400k miles with the straight 6 and a np435 (original owner used to drive from CT-OK once a month for 20 years) I made the mistake of swapping in a 400m and it ruined the truck, about 4 years ago I bought another one with the 300 I love it.

[nic55kel]

Names Ryan, still trying to set up my signature picture and info. Sorry thought I read it was 4.10's, you should be fine. I am of the belief that the ford 300 might be the best motor they ever made. Years ago I had an 85 f150 reg. cab flareside 2wd that I drove for years it had over 400k miles with the straight 6 and a np435 (original owner used to drive from CT-OK once a month for 20 years) I made the mistake of swapping in a 400m and it ruined the truck, about 4 years ago I bought another one with the 300 I love it.

Hi Ryan,

The donor truck has a Dana 60 rear and it has the 4.10 gears.

The 86 truck that the engine and transmission are going into have the 3.55 Sterling.

I completely agree with you regarding the 300.

If you are happy with an old school truck that isn't going to win any races it is a superb engine.

It is simple, reliable, reasonably economical for the day and just does its' job.

I had an 86 reg cab, long box rwd with a 300 and NP 435 and I loved that truck for what it was.

It was like driving 6 cylinder cars and trucks from the 60's and so easy to work on.

Unfortunately rust killed it and I replaced it with the 86 that is the basis for this project.

At first I was excited about having a diesel, I am a diesel mechanic, but I soon got sick of the noise and smoke.

The diesel always had a bad case of piston slap that never completely went away.

I even took the radio out of the truck because there was no point.

Raining here for the next 2 or 3 days and I am also waiting for a gasket set for the engine so I can reseal it.

So I have time to read some more of the posts here.

[nic55kel]

Hi Ryan,

The donor truck has a Dana 60 rear and it has the 4.10 gears.

The 86 truck that the engine and transmission are going into have the 3.55 Sterling.

I completely agree with you regarding the 300.

If you are happy with an old school truck that isn't going to win any races it is a superb engine.

It is simple, reliable, reasonably economical for the day and just does its' job.

I had an 86 reg cab, long box rwd with a 300 and NP 435 and I loved that truck for what it was.

It was like driving 6 cylinder cars and trucks from the 60's and so easy to work on.

Unfortunately rust killed it and I replaced it with the 86 that is the basis for this project.

At first I was excited about having a diesel, I am a diesel mechanic, but I soon got sick of the noise and smoke.

The diesel always had a bad case of piston slap that never completely went away.

I even took the radio out of the truck because there was no point.

Raining here for the next 2 or 3 days and I am also waiting for a gasket set for the engine so I can reseal it.

So I have time to read some more of the posts here.

Hopefully we are coming to the end of this wet stretch. We really needed the rain and we got it.

Starting to clean things up a bit and working on changing the leaking gaskets.

Very happy to see that the cam gear is cast iron.

I can still see some of the cross hatch on the travelled sections of cylinder wall that I can see from the crankcase so very happy about the condition of this engine.