no forward gear on th350. worked until i resealed transfer case.

[BigBlue22]

resealed transfer case. reinstalled and backed out of the garage. That is where it stayed. Put into first gear and nothing. Motor revs but no go. Any suggestions.

 

[HotRodPC]

resealed transfer case. reinstalled and backed out of the garage. That is where it stayed. Put into first gear and nothing. Motor revs but no go. Any suggestions.

But you have reverse? I'd be leaning more towards something in the Tcase isn't right.

 

[HotRodPC]

Ok wait !!! And let me ask this. So this is an NP203 in a 78 Right? Did you get the front driveshaft put back in yet? On an NP203, you need a front driveshaft, ORR put it in 4H Loc and see if it works then.

This is because NP203 is a full time Tcase, and works like a differential between the front and rear axles.

 

[BigBlue22]

Both shafts are in. and it is a 350/350/205

 

[HotRodPC]

But you have reverse??? I do believe Th350/NP205 uses a coupler too. Are you positive you didn't forget to put the coupler to the output shaft if one is required? Or am I getting confused with the NP203 again?

I'd say it's going to be a simple fix buddy. Something backwards or forgotten or something simple like that. Hopefully some back up ideas or help will be here soon. But, do answer if you have reverse or not. That's important to know.

 

[BigBlue22]

Thanks for responding. I do have the coupler installed. I do have reverse. I have been reading alot about people loosing the forward clutch packs and that means rebuild. Hoping its not that. I have had 4 of these trucks in the past but all manual. This is my first issue with an auto.

 

[HotRodPC]

Well yes, that's certainly true. If you have reverse, then your low/reverse clutch pack and your direct clutch pack are fine and you'd have lost your forward clutch pack. But, it seems strange all worked fine until you pulled the Tcase and now the trans don't work. I find that quite ironic. So I'm trying to think of what you could have done to the Tcase.

Now you took the case out of the truck for a reseal right? Didn't split the case for anything?

 

[BigBlue22]

Thats right. I only replaced the seals. The transmission was dumping into the tcase and blowing fluid out the vent when i got up to about 45. New seals front and rear drive shaft and adapter plate, new o-ring on input from transmission. Have had an issue with the truck seeming under powered even though the engine is a fresh build. After I posted is when I found the info about the clutch packs. Would make some sense with all of that put together. Out for tonight Thanks for the help.

 

[BigBlue22]

OK so if it is the clutch pack what rebuild kit do you guys recommend. I have looked around and there are too many out there to figure it out. I would like to go with a good duty kit. I am running 4" lift with 35's and .308 gears. Also while I am at it what gear should I use. I have run all of the calculations and they say a .373 would do it but the guys i know all say .411s. Again thanks for looking at this and any help you can give.

 

[HotRodPC]

OK so if it is the clutch pack what rebuild kit do you guys recommend. I have looked around and there are too many out there to figure it out. I would like to go with a good duty kit. I am running 4" lift with 35's and .308 gears. Also while I am at it what gear should I use. I have run all of the calculations and they say a .373 would do it but the guys i know all say .411s. Again thanks for looking at this and any help you can give.

Yep, those 3.08's will kill a trans with 35's. With 35's I too would run 4.10's. 3.73 is the bare minimun. You're talking a bit over 1/4 of 1 single turn difference. 35's are heavy tires, they are also 12.50 wide so that means you have 50 inches of tires creating friction on the pavement. Also lifted higher, means more wind drag. Some guys even go with 4.56's as a minumum. You're not running an OD trans and Th350's are fairly durable so you can get by with 3.73's if you want to. But all things considered, with 35's you can run without an OD and still run 65-70mph and still be cruising at just under 3000 rpm. Not good on fuel, but you're not going to anyway with those size tires. 3.73's would have you at just under 2700 rpm @ 70. Anything you can do to take strain off your powertrain is wise. Lower gears is the best way to do that.

If all you're wanting to do is replace clutches, just do a banner kit. 95% of the time, your steels are reusuable. If they are severly burnt and have colors on them like blue and yellow where they got so hot they glazed them replace them. Bushings a Th350 are USUALLY reuseable even with a little wear just long as they aren't so thin or gouged up. You could get just the common bushings if you want, but then you need a way to install them too. Here is a Banner kit. http://www.transmissionpartsusa.com/350_Transmission_banner_kit_p/470-000047015.htm
Nylon filters are good, if you don't use this type, go with Dacron.
http://www.transmissionpartsusa.com/TH350_Transmission_filter_p/470-000047922.htm

I've also got a Th350 Rebuild Thread in the Auto Trans section. If you try to do it, and have questions, just ask.

 

[BigBlue22]

Thanks for the info. I am running low on funds to get this thing on the road and the wife is running out of patience using her car to tote trash to dump. I will look into the items you listed and see what i can do. Thanks again.

 

[HotRodPC]

What you might do, is look over these 2 threads. 1 is disassembly, the other the build of a Th350. Look them over good and see if it's something you think you can tackle yourself before you tear it down. No trans builder likes doing a transmission that someone else tore apart then it brought to them in a basket to put together. That's how you tend to forget things like thrust washers or snap rings. Of course I don't mind to much on Th350 and Th400's. I've done enough of them, I can usually do them in my sleep having a nightmare or a wet dream bangin Ole Girl !!!

Disassembly
http://www.gmsquarebody.com/forum/showthread.php?t=911

Build
http://www.gmsquarebody.com/forum/showthread.php?t=1045

BTW, Moving this thread to Auto Transmission Category, so if you have it bookmarked, it's not going to work now and you'll have to re bookmark it in it's correct category.

 

[BigBlue22]

Read the disassembly last night and most of the assembly. Great information. As soon as I have the funds I think I will take a shot at the build. Thank you for all of the information on this site that you have added. All very good and insightful. What kit would you recommend for a rebuild? Would it still be that same one that you discussed earlier? I think that this tranny was run pretty hard before I got it.

 

[HotRodPC]

Th350's are fairly tough. Tougher than what most think since everyone gives all the credit to Th400 for being strong. True, you can't barely beat the strength of a Th400, but still Th350's aren't to bad. I've used Th350's for drag racing in the high 11's low 12's and they help up fine until they broke something like a sprag or input shaft which are about the only 2 hard parts that are common breaks. That kit I suggested is fine unless you burnt up steels. And then depending on the condition of your bushings you might to replace those as needed. As far as strength, you might want to get a hardened outer race gear for the intermediate roller clutch. Be sure to get a USA made one and not a China hunk of ****. You can get them on eBay.