Hey y'all! Fully installed a new rebuild transmission but realized I forgot one of the dowel pins that goes between the transmission and engine block. I got the one closer to the front of the car (on the right when looking at the rear main seal side), but forgot the one to the back of the car (left when looking from rear main seal side). It all bolted up fine and drives fine, but just for good measure should I separate the two and pop the pin in or am I good? Thanks in advance!

 

The dowel pin is there to help align everything up. if everything bolts up and drives fine then it's not necessary.

 

Perfect, thank you! That's what I was thinking as well, but I saw some horror stories of people who forgot them between the head and block of the engine and had pistons blowing holes where they shouldn't be, so was wondering if something could slip out of place over time

Thank you again!

 

I don't agree. The dual dowel pins are to prevent torsional twisting and is why they are an exact fit. The bolts, on the other hand, have a mm or two of play in the holes and as the motor torques the transmission, the transmission will twist over time the 1 or 2 mm which will then throw the alignment off of the input shaft and put added stress on it and all the bearings.

 

Dowel pins were put there for a reason... and TomCat39 explained it perfectly. OP, if you intend to drive the car in a spirited manner... EVER... then remove the transmission and re-install the missing dowel pin. If you drive the car like a granny and NEVER get on it... you might not cause any damage leaving out a dowel pin, but this is no guarantee. Better safe than sorry.

 

The misalignment possible with a pin missing is an order of magnitude greater than what is possible with the both pins installed. It's not going to move with the screws tight, but it may not be aligned precisely either. Clutch alignment is the primary means of alignment, but leaving a pin out is just asking for trouble. The forces on the bearings from misalignment are enough to cause premature failure regardless of how you drive.

 

OK y'all, I attempted a split between the engine and transmission today but wasn't about to rip the entire thing apart just for the single damn pin. Got it about 5mm apart, needed 20mm for the pin to fit, and the way it was set up if I went too far the entire thing would've fallen out. So, I've made the decision to just leave the pin out, undo my half-a-transmission job, and give it to the next owner (in a week), and let them know about the increased risk of misalignment and to pop the pin in during the next trans job. Whether that changes the price is up to them. Thank you all for your help once more!

 

Your so close! Why give up on something so easy. Just have a jack to support the tranny and use your muscles! At least you attempted it. With out the dowel, the first bearing to go will be the pilot bearing by premature wear..

 

Alright my guilt got the better of me and the buyer lowballed me so I said **** it and tried putting the pin in without dropping the transmission. I got it in eventually and got to keep the axles and bitch pin inserted, but for some reason the transmission would only move out 18mm instead of just dropping down, but there should have been nothing preventing its movement (shifter support removed, right LCA separated allowing axle to move). Instead of dropping it completely, I just ground the pin down by 2mm and made it fit. After many attempts and fails I finally got the pin in, so I'll see how it drives tomorrow and pray I didn't stick it in the wrong hole or something (it's kinda hard to see when you only have 18mm to look through). The timer says I took 6 hours and 11 minutes, which ironically means it probably would've been quicker to just drain the damn tranny, pull the axles and do it the right way, but what's done is done and now I pray I didn't **** up the ISB or pilot bearing with all my wrenching of the transmission around.


I hate cars.

 

Good job! It will be fine now. You should have no problems and your car thanks you lol 🙂