88 E350 won't go into 3rd - Diesel Forum

CarbotechMatt · 06-29-2004, 07:52 AM

I just seem to keep having problems.

My recently acquired 88 E350 7.3L is turning into a money pit. Everything worked well on it when I test drove it.

The latest is now when I put it into "Drive", the trans stays in 1st gear. 25mph, the engine is screaming and about to leap out of the van and it still stays in 1st. If I manually shift to "2", it will go into 2nd. If I then shift back to "D", it stays in 2nd, but will still not shift to 3rd at all ever.

The trans fluid level is fine. I am changing the filter later this week. Any other suggestions?? Are there any electronics I should check? The fact that when I shift to "2" and it goes into that gear tells me it is completely capable of doing it, something is telling it not to.

I think this van hates me....

toalpi · 06-29-2004, 10:37 AM

Is this a C6? If not then disregard. Sounds like a possible problem with a vacuum actuated valve that is mounted on the right lower side of the transmission. It is held in with a small bolt and it has a rubber vacuum line connected to it. Possibly called a 'modulator valve'. Any sign of fluid when you pull the hose off definitely means the valve is faulty.

CarbotechMatt · 06-29-2004, 05:14 PM

[ QUOTE ]
Is this a C6?

[/ QUOTE ]

I dunno. What's a C6?? I mean, besides the new Corvette...

toalpi · 06-29-2004, 11:40 PM

[ QUOTE ]
I dunno. What's a C6?? I mean, besides the new Corvette

[/ QUOTE ] If you have a new Corvette you should park the van.

CarbotechMatt · 06-30-2004, 10:54 PM

Problem solved. I'm an idiot is what it comes down to. As I was changing the fuel filter (a fiasco in itself) I knocked some sort of vacuum line off that made the trans not want to shift.

All 3 speeds present and accounted for....

firedane · 07-01-2004, 01:22 AM

Yep - you whacked the vaccum line to the shift modulator valve. That puts the trans into stuck mode. Previous reply right on the money. It is a vaccum dashpot bolted to the tranny. If your 88 is like my 89 it has a C-6. It won't win any awards for gas mileage, but a C-6 is about as tough as they come. Ranks right there with the old Dodge 727 Torqueflite and the GM Turbo 400. Sometimes older and simpler is good.
Watch the screws that hold the screen on the valve body. They are not all the same length. Also, it is not hard to overtorque those little ones and strip the threads in the valve body.

firedane · 07-01-2004, 01:32 AM

Sorry for 2nd post. When you remove the filter from the valve body make sure you duck. Another quart of fluid will come your way!! Look for a kit that has the black fiber pan gasket with 4 holes a little smaller than the rest. They hold 4 bolts to the pan and the gasket in line for easier replacement. Also, I like the filter with the crushable metal gasket. It holds position and doesnt squish out like some of the paper ones. Clean the rails and pan and put the gasket on dry. Torque properly and then recheck it after a couple of days. Sometimes the gasket takes a compression set and will leak a few drops. No RTV silicone here. If even a small bit sucks into the trans, it will plug up the hydraulic passages. Some people use a bit of grease on the gasket to get it to stick in place. I prefer super-clean and dry.

Good luck-
Firedane

CarbotechMatt · 07-01-2004, 12:26 PM

If a 3-speed non-overdrive is a C6 trans, then that's what I have.

[ QUOTE ]
It won't win any awards for gas mileage, but a C-6 is about as tough as they come.

[/ QUOTE ]

Well, the previous owner reported 16mpg towing an enclosed trailer with a race car. My fiends with big block Chevys get 11. So I think 40% better mileage on fuel that costs 25% less is pretty award winning [img]/ubbthreads/images/graemlins/smile.gif[/img]

toalpi · 07-01-2004, 02:31 PM

[ QUOTE ]
the previous owner reported 16mpg towing an enclosed trailer with a race car.

[/ QUOTE ] He must have been towing his Corvette. [img]/ubbthreads/images/graemlins/smirk.gif[/img]